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<button class="button is-small is-link">Go</button> </div> </div> </form> </div> </div> <nav class="pagination is-small is-centered breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" class="pagination-previous is-invisible">Previous </a> <a href="/search/?searchtype=author&query=Sander%2C+A&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Sander%2C+A&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Sander%2C+A&start=50" class="pagination-link " aria-label="Page 2" aria-current="page">2 </a> </li> <li> <a href="/search/?searchtype=author&query=Sander%2C+A&start=100" class="pagination-link " aria-label="Page 3" aria-current="page">3 </a> </li> </ul> </nav> <ol class="breathe-horizontal" start="1"> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2411.14149">arXiv:2411.14149</a> <span> [<a href="https://arxiv.org/pdf/2411.14149">pdf</a>, <a href="https://arxiv.org/format/2411.14149">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> X-Shooting ULLYSES: Massive Stars at Low Metallicity X. Physical Parameters and Feedback of Massive Stars in the LMC N11 B Star-Forming Region </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=G%C3%B3mez-Gonz%C3%A1lez%2C+V+M+A">V. M. A. G贸mez-Gonz谩lez</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L+M">L. M. Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=Hamann%2C+W+-">W. -R. Hamann</a>, <a href="/search/astro-ph?searchtype=author&query=Todt%2C+H">H. Todt</a>, <a href="/search/astro-ph?searchtype=author&query=Pauli%2C+D">D. Pauli</a>, <a href="/search/astro-ph?searchtype=author&query=Serantes%2C+S+R">S. Reyero Serantes</a>, <a href="/search/astro-ph?searchtype=author&query=Bernini-Peron%2C+M">M. Bernini-Peron</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+C">A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">V. Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J+S">J. S. Vink</a>, <a href="/search/astro-ph?searchtype=author&query=Crowther%2C+P+A">P. A. Crowther</a>, <a href="/search/astro-ph?searchtype=author&query=Berlanas%2C+S+R">S. R. Berlanas</a>, <a href="/search/astro-ph?searchtype=author&query=ud-Doula%2C+A">A. ud-Doula</a>, <a href="/search/astro-ph?searchtype=author&query=Gormaz-Matamala%2C+A+C">A. C. Gormaz-Matamala</a>, <a href="/search/astro-ph?searchtype=author&query=Kehrig%2C+C">C. Kehrig</a>, <a href="/search/astro-ph?searchtype=author&query=Kuiper%2C+R">R. Kuiper</a>, <a href="/search/astro-ph?searchtype=author&query=Leitherer%2C+C">C. Leitherer</a>, <a href="/search/astro-ph?searchtype=author&query=Mahy%2C+L">L. Mahy</a>, <a href="/search/astro-ph?searchtype=author&query=McLeod%2C+A+F">A. F. McLeod</a>, <a href="/search/astro-ph?searchtype=author&query=Mehner%2C+A">A. Mehner</a>, <a href="/search/astro-ph?searchtype=author&query=Morrell%2C+N">N. Morrell</a>, <a href="/search/astro-ph?searchtype=author&query=Shenar%2C+T">T. Shenar</a>, <a href="/search/astro-ph?searchtype=author&query=Telford%2C+O+G">O. G. Telford</a>, <a href="/search/astro-ph?searchtype=author&query=van+Loon%2C+J+T">J. Th. van Loon</a>, <a href="/search/astro-ph?searchtype=author&query=Tramper%2C+F">F. Tramper</a> , et al. (1 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2411.14149v1-abstract-short" style="display: inline;"> Massive stars lead the ionization and mechanical feedback within young star-forming regions. The Large Magellanic Cloud (LMC) is an ideal galaxy for studying individual massive stars and quantifying their feedback contribution to the environment. We analyze eight exemplary targets in LMC N11 B from the Hubble UV Legacy Library of Young Stars as Essential Standards (ULLYSES) program, using novel sp… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.14149v1-abstract-full').style.display = 'inline'; document.getElementById('2411.14149v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2411.14149v1-abstract-full" style="display: none;"> Massive stars lead the ionization and mechanical feedback within young star-forming regions. The Large Magellanic Cloud (LMC) is an ideal galaxy for studying individual massive stars and quantifying their feedback contribution to the environment. We analyze eight exemplary targets in LMC N11 B from the Hubble UV Legacy Library of Young Stars as Essential Standards (ULLYSES) program, using novel spectra from HST (COS and STIS) in the UV, and from VLT (X-shooter) in the optical. We model the spectra of early to late O-type stars by using state-of-the-art PoWR atmosphere models. We determine the stellar and wind parameters (e.g., $T_\star$, $\log g$, $L_{\star}$, $\dot{M}$, $v_\infty$) of the analyzed objects, chemical abundances (C, N, O), ionizing and mechanical feedback ($Q_\mathrm{H}$, $Q_\mathrm{He{\small{I}}}$, $Q_\mathrm{He{\small{II}}}$, $L_\mathrm{mec}$) and X-rays. We report ages of $2-4.5$ Myr and masses of $30-60$ $M_\odot$ for the analyzed stars in N11 B, consistent with a scenario of sequential star formation. We note that the observed wind-momentum luminosity relation is consistent with theoretical predictions. We detect nitrogen enrichment in most of the stars, up to a factor of seven. However, we do not find a correlation between nitrogen enrichment and projected rotational velocity. Finally, based on their spectral type, we estimate the total ionizing photons injected from the O-type stars in N11 B into its environment. We report $\log$ ($\sum$ $Q_\mathrm{H}$)$=50.5$ ph s$^{-1}$, $\log$ ($\sum$ $Q_\mathrm{He{\small{I}}}$)$=49.6$ ph s$^{-1}$ and $\log$ ($\sum$ $Q_\mathrm{He{\small{II}}}$)$=44.4$ ph s$^{-1}$, consistent with the total ionizing budget in N11. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.14149v1-abstract-full').style.display = 'none'; document.getElementById('2411.14149v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 November, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted in Astronomy and Astrophysics</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2411.06884">arXiv:2411.06884</a> <span> [<a href="https://arxiv.org/pdf/2411.06884">pdf</a>, <a href="https://arxiv.org/format/2411.06884">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> X-Shooting ULLYSES: Massive stars at low metallicity VI. Atmosphere and mass-loss properties of O-type giants in the Small Magellanic Cloud </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Backs%2C+F">Frank Backs</a>, <a href="/search/astro-ph?searchtype=author&query=Brands%2C+S+A">S. A. Brands</a>, <a href="/search/astro-ph?searchtype=author&query=de+Koter%2C+A">A. de Koter</a>, <a href="/search/astro-ph?searchtype=author&query=Kaper%2C+L">L. Kaper</a>, <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J+S">J. S. Vink</a>, <a href="/search/astro-ph?searchtype=author&query=Puls%2C+J">J. Puls</a>, <a href="/search/astro-ph?searchtype=author&query=Sundqvist%2C+J">J. Sundqvist</a>, <a href="/search/astro-ph?searchtype=author&query=Tramper%2C+F">F. Tramper</a>, <a href="/search/astro-ph?searchtype=author&query=Sana%2C+H">H. Sana</a>, <a href="/search/astro-ph?searchtype=author&query=Bernini-Peron%2C+M">M. Bernini-Peron</a>, <a href="/search/astro-ph?searchtype=author&query=Bestenlehner%2C+J+M">J. M. Bestenlehner</a>, <a href="/search/astro-ph?searchtype=author&query=Crowther%2C+P+A">P. A. Crowther</a>, <a href="/search/astro-ph?searchtype=author&query=Hawcroft%2C+C">C. Hawcroft</a>, <a href="/search/astro-ph?searchtype=author&query=Ignace%2C+R">R. Ignace</a>, <a href="/search/astro-ph?searchtype=author&query=Kuiper%2C+R">R. Kuiper</a>, <a href="/search/astro-ph?searchtype=author&query=van+Loon%2C+J+T">J. Th. van Loon</a>, <a href="/search/astro-ph?searchtype=author&query=Mahy%2C+L">L. Mahy</a>, <a href="/search/astro-ph?searchtype=author&query=Marcolino%2C+W">W. Marcolino</a>, <a href="/search/astro-ph?searchtype=author&query=Najarro%2C+F">F. Najarro</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L+M">L. M. Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=Pauli%2C+D">D. Pauli</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">V. Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Verhamme%2C+O">O. Verhamme</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2411.06884v1-abstract-short" style="display: inline;"> Mass loss through a stellar wind is an important physical process that steers the evolution of massive stars and controls the properties of their end-of-life products, such as the supernova type and the mass of compact remnants. For an accurate mass loss determination, the inhomogeneities in the wind, known as clumping, needs to be taking into account. We aim to improve empirical estimates of mass… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.06884v1-abstract-full').style.display = 'inline'; document.getElementById('2411.06884v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2411.06884v1-abstract-full" style="display: none;"> Mass loss through a stellar wind is an important physical process that steers the evolution of massive stars and controls the properties of their end-of-life products, such as the supernova type and the mass of compact remnants. For an accurate mass loss determination, the inhomogeneities in the wind, known as clumping, needs to be taking into account. We aim to improve empirical estimates of mass loss and wind clumping for hot main-sequence massive stars, study the dependence of both properties on the metallicity, and compare the theoretical predictions to our findings. We analyzed the optical and UV spectra of 13 O-type stars in the Small Magellanic Cloud galaxy, which has a metallicity of $\sim 0.2\,Z_\odot$. We quantified the stellar atmosphere, outflow, and wind-clumping properties. To probe the role of metallicity, we compared our findings to studies of Galactic and Large Magellanic Cloud samples that were analyzed with similar methods. We find significant variations in the wind-clumping properties of the target stars, with clumping starting at flow velocities $0.01 - 0.23$ of the terminal wind velocity and reaching clumping factors $f_{\rm cl} = 2 - 30$. In the luminosity ($\log L / L_{\odot} = 5.0 - 6.0$) and metallicity ($Z/Z_{\odot} = 0.2 - 1$) range we considered, we find that the scaling of the mass loss $\dot{M}$ with metallicity $Z$ varies with luminosity. At $\log L/L_{\odot} = 5.75$, we find $\dot{M} \propto Z^m$ with $m = 1.02 \pm 0.30$, in agreement with pioneering work in the field. For lower luminosities, however, we obtain a significantly steeper scaling of $m > 2$. The monotonically decreasing $m(L)$ behavior adds a complexity to the functional description of the mass-loss rate of hot massive stars. Although the trend is present in the predictions, it is much weaker than we found here. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.06884v1-abstract-full').style.display = 'none'; document.getElementById('2411.06884v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 11 November, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">37 pages, 29 figures. Accepted for publication in Astronomy and Astrophysics</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2411.02484">arXiv:2411.02484</a> <span> [<a href="https://arxiv.org/pdf/2411.02484">pdf</a>, <a href="https://arxiv.org/format/2411.02484">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> Winds of change: why binary black hole formation is metallicity dependent, while binary neutron star formation is not </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=van+Son%2C+L+A+C">L. A. C. van Son</a>, <a href="/search/astro-ph?searchtype=author&query=Roy%2C+S+K">S. K. Roy</a>, <a href="/search/astro-ph?searchtype=author&query=Mandel%2C+I">I. Mandel</a>, <a href="/search/astro-ph?searchtype=author&query=Farr%2C+W+M">W. M. Farr</a>, <a href="/search/astro-ph?searchtype=author&query=Lam%2C+A">A. Lam</a>, <a href="/search/astro-ph?searchtype=author&query=Merritt%2C+J">J. Merritt</a>, <a href="/search/astro-ph?searchtype=author&query=Broekgaarden%2C+F+S">F. S. Broekgaarden</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A">A. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Andrews%2C+J+J">J. J. Andrews</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2411.02484v1-abstract-short" style="display: inline;"> Both detailed and rapid population studies alike predict that binary black hole (BHBH) formation is orders of magnitude more efficient at low metallicity than high metallicity, while binary neutron star (NSNS) formation remains mostly flat with metallicity, and black hole-neutron star (BHNS) mergers show intermediate behavior. This finding is a key input to employ double compact objects as tracers… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.02484v1-abstract-full').style.display = 'inline'; document.getElementById('2411.02484v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2411.02484v1-abstract-full" style="display: none;"> Both detailed and rapid population studies alike predict that binary black hole (BHBH) formation is orders of magnitude more efficient at low metallicity than high metallicity, while binary neutron star (NSNS) formation remains mostly flat with metallicity, and black hole-neutron star (BHNS) mergers show intermediate behavior. This finding is a key input to employ double compact objects as tracers of low-metallicity star formation, as spectral sirens, and for merger rate calculations. Yet, the literature offers various (sometimes contradicting) explanations for these trends. We investigate the dominant cause for the metallicity dependence of double compact object formation. We find that the BHBH formation efficiency at low metallicity is set by initial condition distributions, and conventional simulations suggest that about one in eight interacting binary systems with sufficient mass to form black holes will lead to a merging BHBH. We further find that the significance of metallicities in double compact object formation is a question of formation channel. The stable mass transfer and chemically homogeneous evolution channels mainly diminish at high metallicities due to changes in stellar radii, while the common envelope channel is primarily impacted by the combined effects of stellar winds and mass-scaled natal kicks. Outdated giant wind prescriptions exacerbate the latter effect, suggesting BHBH formation may be much less metallicity dependent than previously assumed. NSNS formation efficiency remains metallicity independent as they form exclusively through the common envelope channel, with natal kicks that are uncorrelated with mass. Forthcoming GW observations will provide valuable constraints on these findings <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.02484v1-abstract-full').style.display = 'none'; document.getElementById('2411.02484v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 4 November, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">14 pages, 8 Figures, Submitted to ApJ, Scripts and data to reproduce this work are at https://github.com/LiekeVanSon/ZdependentFormEff , and https://zenodo.org/records/13999532</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2410.14937">arXiv:2410.14937</a> <span> [<a href="https://arxiv.org/pdf/2410.14937">pdf</a>, <a href="https://arxiv.org/format/2410.14937">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> X-Shooting ULLYSES: Massive Stars at low metallicity IX: Empirical constraints on mass-loss rates and clumping parameters for OB supergiants in the Large Magellanic Cloud </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Verhamme%2C+O">O. Verhamme</a>, <a href="/search/astro-ph?searchtype=author&query=Sundqvist%2C+J">J. Sundqvist</a>, <a href="/search/astro-ph?searchtype=author&query=de+Koter%2C+A">A. de Koter</a>, <a href="/search/astro-ph?searchtype=author&query=Sana%2C+H">H. Sana</a>, <a href="/search/astro-ph?searchtype=author&query=Backs%2C+F">F. Backs</a>, <a href="/search/astro-ph?searchtype=author&query=Brands%2C+S+A">S. A. Brands</a>, <a href="/search/astro-ph?searchtype=author&query=Najarro%2C+F">F. Najarro</a>, <a href="/search/astro-ph?searchtype=author&query=Puls%2C+J">J. Puls</a>, <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J+S">J. S. Vink</a>, <a href="/search/astro-ph?searchtype=author&query=Crowther%2C+P+A">P. A. Crowther</a>, <a href="/search/astro-ph?searchtype=author&query=Kub%C3%A1tov%C3%A1%2C+B">B. Kub谩tov谩</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Bernini-Peron%2C+M">M. Bernini-Peron</a>, <a href="/search/astro-ph?searchtype=author&query=Kuiper%2C+R">R. Kuiper</a>, <a href="/search/astro-ph?searchtype=author&query=Prinja%2C+R+K">R. K. Prinja</a>, <a href="/search/astro-ph?searchtype=author&query=Schillemans%2C+P">P. Schillemans</a>, <a href="/search/astro-ph?searchtype=author&query=Shenar%2C+T">T. Shenar</a>, <a href="/search/astro-ph?searchtype=author&query=van+Loon%2C+J+T">J. Th. van Loon</a>, <a href="/search/astro-ph?searchtype=author&query=collaboration%2C+X">XShootu collaboration</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2410.14937v2-abstract-short" style="display: inline;"> Context. Current implementations of mass loss for hot, massive stars in stellar evolution models include a sharp increase in mass loss when blue supergiants become cooler than Teff 20-22kK. This drastic mass-loss jump has been motivated by the potential presence of a so-called bistability ionisation effect, which may occur for line-driven winds in this temperature region due to recombination of im… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.14937v2-abstract-full').style.display = 'inline'; document.getElementById('2410.14937v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2410.14937v2-abstract-full" style="display: none;"> Context. Current implementations of mass loss for hot, massive stars in stellar evolution models include a sharp increase in mass loss when blue supergiants become cooler than Teff 20-22kK. This drastic mass-loss jump has been motivated by the potential presence of a so-called bistability ionisation effect, which may occur for line-driven winds in this temperature region due to recombination of important line-driving ions. Aims. We perform quantitative spectroscopy using UV (ULLYSES program) and optical (XShootU collaboration) data for 17 OB-supergiant stars in the LMC (covering the range Teff 14-32kK), deriving absolute constraints on global stellar, wind, and clumping parameters. We examine whether there are any empirical signs of a mass-loss jump in the investigated region, and we study the clumped nature of the wind. Methods. We use a combination of the model atmosphere code fastwind and the genetic algorithm code Kiwi-GA to fit synthetic spectra of a multitude of diagnostic spectral lines in the optical and UV. Results. We find no signs of any upward mass loss jump anywhere in the examined region. Standard theoretical comparison models, which include a strong bistability jump thus severely over predict the empirical mass-loss rates on the cool side of the predicted jump. Additionally, we find that on average about 40% of the total wind mass seems to reside in the diluted medium in between dense clumps. Conclusions. Our derived mass-loss rates suggest that for applications like stellar evolution one should not include a drastic bistability jump in mass loss for stars in the temperature and luminosity region investigated here. The derived high values of interclump density further suggest that the common assumption of an effectively void interclump medium (applied in the vast majority of spectroscopic studies of hot star winds) is not generally valid in this parameter regime. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.14937v2-abstract-full').style.display = 'none'; document.getElementById('2410.14937v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 October, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 18 October, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2410.12484">arXiv:2410.12484</a> <span> [<a href="https://arxiv.org/pdf/2410.12484">pdf</a>, <a href="https://arxiv.org/format/2410.12484">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> Hot Star Winds </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2410.12484v1-abstract-short" style="display: inline;"> The properties, impact, and fate of hot stars cannot be understood without considering their winds. Revealed to be an almost ubiquitous phenomenon in the regime of massive stars, the winds of hot stars arise from a complex physical mechanism that still provides a major challenge for our understanding of massive stars. Different flavours of hot stars vary significantly in their winds with current e… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.12484v1-abstract-full').style.display = 'inline'; document.getElementById('2410.12484v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2410.12484v1-abstract-full" style="display: none;"> The properties, impact, and fate of hot stars cannot be understood without considering their winds. Revealed to be an almost ubiquitous phenomenon in the regime of massive stars, the winds of hot stars arise from a complex physical mechanism that still provides a major challenge for our understanding of massive stars. Different flavours of hot stars vary significantly in their winds with current evolution models still having problems to connect the zoo of observed phenomena. Moreover, the driving of hot star winds is inherently connected to the opacities arising from spectral line transitions, making the properties and strength of the winds strongly dependent on metallicity and changing them over cosmic time. In these proceedings, the current status in our understanding of hot star winds is briefly reviewed and recent progress in our perception of hot star winds and the consequences for the evolution of massive stars are presented. A particular emphasis is given on current efforts with hydrodynamically-consistent atmosphere models towards a better description of radiatively-driven mass loss of Wolf-Rayet stars with remaining hydrogen envelopes. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.12484v1-abstract-full').style.display = 'none'; document.getElementById('2410.12484v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 October, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">4 pages, 3 figures, to be published in the International Astronomical Union Proceedings Series for the IAU GA 2024 (Astronomy in Focus, Focus Meeting 4 "Bridging the final stages of massive stars to supernovae and transients")</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2409.15212">arXiv:2409.15212</a> <span> [<a href="https://arxiv.org/pdf/2409.15212">pdf</a>, <a href="https://arxiv.org/format/2409.15212">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> Investigating 39 Galactic Wolf-Rayet stars with VLTI/GRAVITY: Uncovering A Long Period Binary Desert </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Deshmukh%2C+K">K. Deshmukh</a>, <a href="/search/astro-ph?searchtype=author&query=Sana%2C+H">H. Sana</a>, <a href="/search/astro-ph?searchtype=author&query=M%C3%A9rand%2C+A">A. M茅rand</a>, <a href="/search/astro-ph?searchtype=author&query=Bordier%2C+E">E. Bordier</a>, <a href="/search/astro-ph?searchtype=author&query=Langer%2C+N">N. Langer</a>, <a href="/search/astro-ph?searchtype=author&query=Bodensteiner%2C+J">J. Bodensteiner</a>, <a href="/search/astro-ph?searchtype=author&query=Dsilva%2C+K">K. Dsilva</a>, <a href="/search/astro-ph?searchtype=author&query=Frost%2C+A+J">A. J. Frost</a>, <a href="/search/astro-ph?searchtype=author&query=Gosset%2C+E">E. Gosset</a>, <a href="/search/astro-ph?searchtype=author&query=Bouquin%2C+J+-+L">J. -B. Le Bouquin</a>, <a href="/search/astro-ph?searchtype=author&query=Lefever%2C+R+R">R. R. Lefever</a>, <a href="/search/astro-ph?searchtype=author&query=Mahy%2C+L">L. Mahy</a>, <a href="/search/astro-ph?searchtype=author&query=Patrick%2C+L+R">L. R. Patrick</a>, <a href="/search/astro-ph?searchtype=author&query=Reggiani%2C+M">M. Reggiani</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Shenar%2C+T">T. Shenar</a>, <a href="/search/astro-ph?searchtype=author&query=Tramper%2C+F">F. Tramper</a>, <a href="/search/astro-ph?searchtype=author&query=Villase%C3%B1or%2C+J+I">J. I. Villase帽or</a>, <a href="/search/astro-ph?searchtype=author&query=Waisberg%2C+I">I. Waisberg</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2409.15212v2-abstract-short" style="display: inline;"> Wolf-Rayet stars (WRs) are one of the final evolutionary stages of massive stars and immediate progenitors of stellar-mass black holes. Their multiplicity forms an important anchor point in single and binary population models for predicting gravitational-wave progenitors. Recent spectroscopic campaigns have suggested incompatible multiplicity fractions and period distributions for N- and C-rich Ga… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2409.15212v2-abstract-full').style.display = 'inline'; document.getElementById('2409.15212v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2409.15212v2-abstract-full" style="display: none;"> Wolf-Rayet stars (WRs) are one of the final evolutionary stages of massive stars and immediate progenitors of stellar-mass black holes. Their multiplicity forms an important anchor point in single and binary population models for predicting gravitational-wave progenitors. Recent spectroscopic campaigns have suggested incompatible multiplicity fractions and period distributions for N- and C-rich Galactic WRs (WNs and WCs) at short as well as long orbital periods, in contradiction with evolutionary model predictions. In this work, we employed infrared interferometry using the $K$-band instrument GRAVITY at the VLTI to investigate the multiplicity of WRs at long periods and explore the nature of their companions. We present a survey of 39 Galactic WRs, including 11 WN, 15 WC and 13 H-rich WN (WNh) stars. We detected wide companions with GRAVITY for only four stars: WR 48, WR 89, WR 93 and WR 115. Combining with spectroscopic studies, we arrived at multiplicity fractions of $f^{\rm WN}_{\rm obs} = 0.55\pm0.15$, $f^{\rm WC}_{\rm obs} = 0.40\pm0.13$ and $f^{\rm WNh}_{\rm obs} = 0.23\pm0.12$. In addition, we also found other features in the GRAVITY dataset such as (i) a diffuse extended component in over half the WR sample; (ii) five known spectroscopic binaries resolved in differential phase data and (iii) spatially resolved winds in four stars: WR 16, WR 31a, WR 78 and WR 110. Our survey reveals a lack of intermediate (few 100s d) and long- (few years to decades) period WR systems. The 200-d peak in the period distributions of WR+OB and BH+OB binaries predicted by Case B mass-transfer binary evolution models is not seen in our data. The rich companionship of their O-type progenitors in this separation range suggest that the WR progenitor stars expand and interact with their companions, most likely through unstable mass-transfer, resulting in either a short-period system or a merger. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2409.15212v2-abstract-full').style.display = 'none'; document.getElementById('2409.15212v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 October, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 23 September, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted in A&A</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2409.12133">arXiv:2409.12133</a> <span> [<a href="https://arxiv.org/pdf/2409.12133">pdf</a>, <a href="https://arxiv.org/format/2409.12133">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202451324">10.1051/0004-6361/202451324 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Multi-wavelength spectroscopic analysis of the ULX Holmberg II X-1 and its nebula suggests the presence of a heavy black hole accreting from a B-type donor </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Serantes%2C+S+R">S. Reyero Serantes</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L">L. Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=Hamann%2C+W+-">W. -R. Hamann</a>, <a href="/search/astro-ph?searchtype=author&query=G%C3%B3mez-Gonz%C3%A1lez%2C+V+M">V. M. G贸mez-Gonz谩lez</a>, <a href="/search/astro-ph?searchtype=author&query=Todt%2C+H">H. Todt</a>, <a href="/search/astro-ph?searchtype=author&query=Pauli%2C+D">D. Pauli</a>, <a href="/search/astro-ph?searchtype=author&query=Soria%2C+R">R. Soria</a>, <a href="/search/astro-ph?searchtype=author&query=Gies%2C+D+R">D. R. Gies</a>, <a href="/search/astro-ph?searchtype=author&query=Torrej%C3%B3n%2C+J+M">J. M. Torrej贸n</a>, <a href="/search/astro-ph?searchtype=author&query=Bulik%2C+T">T. Bulik</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">V. Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Bozzo%2C+E">E. Bozzo</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">J. Poutanen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2409.12133v2-abstract-short" style="display: inline;"> Ultra-luminous X-ray sources (ULXs) are high-mass X-ray binaries with an X-ray luminosity above $10^{39}$ erg s$^{-1}$. These ULXs can be powered by black holes that are more massive than $20M_\odot$, accreting in a standard regime, or lighter compact objects accreting supercritically. There are only a few ULXs with known optical or UV counterparts, and their nature is debated. Determining whether… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2409.12133v2-abstract-full').style.display = 'inline'; document.getElementById('2409.12133v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2409.12133v2-abstract-full" style="display: none;"> Ultra-luminous X-ray sources (ULXs) are high-mass X-ray binaries with an X-ray luminosity above $10^{39}$ erg s$^{-1}$. These ULXs can be powered by black holes that are more massive than $20M_\odot$, accreting in a standard regime, or lighter compact objects accreting supercritically. There are only a few ULXs with known optical or UV counterparts, and their nature is debated. Determining whether optical/UV radiation is produced by the donor star or by the accretion disc is crucial for understanding ULX physics and testing massive binary evolution. We conduct, for the first time, a fully consistent multi-wavelength spectral analysis of a ULX and its circumstellar nebula. We aim to establish the donor star type and test the presence of strong disc winds in the prototypical ULX Holmberg II X-1 (Ho II X-1). We intent to obtain a realistic spectral energy distribution of the ionising source, which is needed for robust nebula analysis. We acquired new UV spectra of Ho II X-1 with the HST and complemented them with archival optical and X-ray data. We explored the spectral energy distribution of the source and analysed the spectra using the stellar atmosphere code PoWR and the photoionisation code Cloudy. Our analysis of the X-ray, UV, and optical spectra of Ho II X-1 and its nebula consistently explains the observations. We do not find traces of disc wind signatures in the UV and the optical, rejecting previous claims of the ULX being a supercritical accretor. The optical/UV counterpart of HoII X-1 is explained by a B-type supergiant donor star. Thus, the observations are fully compatible with Ho II X-1 being a close binary consisting of an $\gtrsim 66\,M_\odot$ black hole accreting matter from an $\simeq 22 M_\odot$ B-supergiant companion. Also, we propose a possible evolution scenario for the system, suggesting that Ho II X-1 is a potential gravitational wave source progenitor. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2409.12133v2-abstract-full').style.display = 'none'; document.getElementById('2409.12133v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 19 September, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 18 September, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted in A&A. 14 pages (12 main body + 2 appendix), 6 figures, 6 tables</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2408.06215">arXiv:2408.06215</a> <span> [<a href="https://arxiv.org/pdf/2408.06215">pdf</a>, <a href="https://arxiv.org/format/2408.06215">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202450928">10.1051/0004-6361/202450928 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Gas-phase Fe/O and Fe/N abundances in Star-Forming Regions. Relations between nucleosynthesis, metallicity and dust </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=M%C3%A9ndez-Delgado%2C+J+E">J. E. M茅ndez-Delgado</a>, <a href="/search/astro-ph?searchtype=author&query=Kreckel%2C+K">K. Kreckel</a>, <a href="/search/astro-ph?searchtype=author&query=Esteban%2C+C">C. Esteban</a>, <a href="/search/astro-ph?searchtype=author&query=Garc%C3%ADa-Rojas%2C+J">J. Garc铆a-Rojas</a>, <a href="/search/astro-ph?searchtype=author&query=Carigi%2C+L">L. Carigi</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Palla%2C+M">M. Palla</a>, <a href="/search/astro-ph?searchtype=author&query=Chru%C5%9Bli%C5%84ska%2C+M">M. Chru艣li艅ska</a>, <a href="/search/astro-ph?searchtype=author&query=De+Looze%2C+I">I. De Looze</a>, <a href="/search/astro-ph?searchtype=author&query=Rela%C3%B1o%2C+M">M. Rela帽o</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Giessen%2C+S+A">S. A. van der Giessen</a>, <a href="/search/astro-ph?searchtype=author&query=Reyes-Rodr%C3%ADguez%2C+E">E. Reyes-Rodr铆guez</a>, <a href="/search/astro-ph?searchtype=author&query=S%C3%A1nchez%2C+S+F">S. F. S谩nchez</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2408.06215v1-abstract-short" style="display: inline;"> In stars, metallicity is usually traced using Fe, while in nebulae, O serves as the preferred proxy. Both elements have different nucleosynthetic origins and are not directly comparable. Additionally, in ionized nebulae, Fe is heavily depleted onto dust grains. We investigate the distribution of Fe gas abundances in a sample of 452 star-forming nebulae with \feiii~$位4658$ detections and their rela… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.06215v1-abstract-full').style.display = 'inline'; document.getElementById('2408.06215v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2408.06215v1-abstract-full" style="display: none;"> In stars, metallicity is usually traced using Fe, while in nebulae, O serves as the preferred proxy. Both elements have different nucleosynthetic origins and are not directly comparable. Additionally, in ionized nebulae, Fe is heavily depleted onto dust grains. We investigate the distribution of Fe gas abundances in a sample of 452 star-forming nebulae with \feiii~$位4658$ detections and their relationship with O and N. Additionally, we analyze the depletion of Fe onto dust grains in photoionized environments. We homogeneously determine the chemical abundances with direct determinations of electron temperature ($T_e$), considering the effect of possible internal variations of this parameter. We adopt a sample of 300 Galactic stars to interpret the nebular findings. We find a moderate linear correlation ($r=-0.59$) between Fe/O and O/H. In turn, we report a stronger correlation ($r=-0.80$) between Fe/N and N/H. We interpret the tighter correlation as evidence of Fe and N being produced on similar timescales while Fe-dust depletion scales with the Fe availability. The apparently flat distribution between Fe/N and N/H in Milky Way stars supports this interpretation. We find that when 12+log(O/H)<7.6, the nebulae seem to reach a plateau value around $\text{log(Fe/O)} \approx -1.7$. If this trend is confirmed, it would be consistent with a very small amount of Fe-dust in these systems, similar to what is observed in high-z galaxies discovered by the James Webb Space Telescope (JWST). We derive a relationship that allows us to approximate the fraction of Fe trapped into dust in ionized nebulae. If the O-dust scales in the same way, its possible contribution in low metallicity nebulae would be negligible. After analyzing the Fe/O abundances in J0811+4730 and J1631+4426, we do not see evidence of the presence of very massive stars with $M_\text{init}>300M_{\odot}$ in these systems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.06215v1-abstract-full').style.display = 'none'; document.getElementById('2408.06215v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 690, A248 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2407.20313">arXiv:2407.20313</a> <span> [<a href="https://arxiv.org/pdf/2407.20313">pdf</a>, <a href="https://arxiv.org/format/2407.20313">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> Observations of Extremely Metal-Poor O Stars: Weak Winds and Constraints for Evolution Models </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Telford%2C+O+G">O. Grace Telford</a>, <a href="/search/astro-ph?searchtype=author&query=Chisholm%2C+J">John Chisholm</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">Varsha Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=McQuinn%2C+K+B+W">Kristen B. W. McQuinn</a>, <a href="/search/astro-ph?searchtype=author&query=Berg%2C+D+A">Danielle A. Berg</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2407.20313v1-abstract-short" style="display: inline;"> Metal-poor massive stars drive the evolution of low-mass galaxies, both locally and at high redshift. However, quantifying the feedback they impart to their local surroundings remains uncertain because models of stellar evolution, mass loss, and ionizing spectra are unconstrained by observations below 20% solar metallicity ($Z_\odot$). We present new Keck Cosmic Web Imager optical spectroscopy of… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.20313v1-abstract-full').style.display = 'inline'; document.getElementById('2407.20313v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2407.20313v1-abstract-full" style="display: none;"> Metal-poor massive stars drive the evolution of low-mass galaxies, both locally and at high redshift. However, quantifying the feedback they impart to their local surroundings remains uncertain because models of stellar evolution, mass loss, and ionizing spectra are unconstrained by observations below 20% solar metallicity ($Z_\odot$). We present new Keck Cosmic Web Imager optical spectroscopy of three O stars in the nearby dwarf galaxies Leo P, Sextans A, and WLM, which have gas-phase oxygen abundances of 3-14% $Z_\odot$. To characterize their fundamental stellar properties and radiation-driven winds, we fit PoWR atmosphere models to the optical spectra simultaneously with Hubble Space Telescope far-ultraviolet (FUV) spectra and multi-wavelength photometry. We find that all three stars have effective temperatures consistent with their spectral types and surface gravities typical of main-sequence dwarf stars. Yet, the combination of those inferred parameters and luminosity for the two lower-$Z$ stars is not reproduced by stellar evolution models, even those that include rotation or binary interactions. The scenario of multiple-star systems is difficult to reconcile with all available data, suggesting that these observations pose a challenge to current evolution models. We highlight the importance of validating the relationship between stellar mass, temperature, and luminosity at very low $Z$ for accurate estimates of ionizing photon production and spectral hardness. Finally, all three stars' FUV wind profiles reveal low mass-loss rates and terminal wind velocities in tension with expectations from widely adopted radiation-driven wind models. These results provide empirical benchmarks for future development of mass-loss and evolution models for metal-poor stellar populations. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.20313v1-abstract-full').style.display = 'none'; document.getElementById('2407.20313v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 29 July, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted at ApJ. 10 figures, 25 pages</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2407.14593">arXiv:2407.14593</a> <span> [<a href="https://arxiv.org/pdf/2407.14593">pdf</a>, <a href="https://arxiv.org/format/2407.14593">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202451586">10.1051/0004-6361/202451586 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Binarity at LOw Metallicity (BLOeM): a spectroscopic VLT monitoring survey of massive stars in the SMC </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Shenar%2C+T">T. Shenar</a>, <a href="/search/astro-ph?searchtype=author&query=Bodensteiner%2C+J">J. Bodensteiner</a>, <a href="/search/astro-ph?searchtype=author&query=Sana%2C+H">H. Sana</a>, <a href="/search/astro-ph?searchtype=author&query=Crowther%2C+P+A">P. A. Crowther</a>, <a href="/search/astro-ph?searchtype=author&query=Lennon%2C+D+J">D. J. Lennon</a>, <a href="/search/astro-ph?searchtype=author&query=Abdul-Masih%2C+M">M. Abdul-Masih</a>, <a href="/search/astro-ph?searchtype=author&query=Almeida%2C+L+A">L. A. Almeida</a>, <a href="/search/astro-ph?searchtype=author&query=Backs%2C+F">F. Backs</a>, <a href="/search/astro-ph?searchtype=author&query=Berlanas%2C+S+R">S. R. Berlanas</a>, <a href="/search/astro-ph?searchtype=author&query=Bernini-Peron%2C+M">M. Bernini-Peron</a>, <a href="/search/astro-ph?searchtype=author&query=Bestenlehner%2C+J+M">J. M. Bestenlehner</a>, <a href="/search/astro-ph?searchtype=author&query=Bowman%2C+D+M">D. M. Bowman</a>, <a href="/search/astro-ph?searchtype=author&query=Bronner%2C+V+A">V. A. Bronner</a>, <a href="/search/astro-ph?searchtype=author&query=Britavskiy%2C+N">N. Britavskiy</a>, <a href="/search/astro-ph?searchtype=author&query=de+Koter%2C+A">A. de Koter</a>, <a href="/search/astro-ph?searchtype=author&query=de+Mink%2C+S+E">S. E. de Mink</a>, <a href="/search/astro-ph?searchtype=author&query=Deshmukh%2C+K">K. Deshmukh</a>, <a href="/search/astro-ph?searchtype=author&query=Evans%2C+C+J">C. J. Evans</a>, <a href="/search/astro-ph?searchtype=author&query=Fabry%2C+M">M. Fabry</a>, <a href="/search/astro-ph?searchtype=author&query=Gieles%2C+M">M. Gieles</a>, <a href="/search/astro-ph?searchtype=author&query=Gilkis%2C+A">A. Gilkis</a>, <a href="/search/astro-ph?searchtype=author&query=Gonz%C3%A1lez-Tor%C3%A0%2C+G">G. Gonz谩lez-Tor脿</a>, <a href="/search/astro-ph?searchtype=author&query=Gr%C3%A4fener%2C+G">G. Gr盲fener</a>, <a href="/search/astro-ph?searchtype=author&query=G%C3%B6tberg%2C+Y">Y. G枚tberg</a>, <a href="/search/astro-ph?searchtype=author&query=Hawcroft%2C+C">C. Hawcroft</a> , et al. (52 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2407.14593v2-abstract-short" style="display: inline;"> Surveys in the Milky Way and Large Magellanic Cloud revealed that the majority of massive stars will interact with companions during their lives. However, knowledge of the binary properties of massive stars at low metallicity, which approaches the conditions of the Early Universe, remains sparse. We present the Binarity at LOw Metallicity (BLOeM) campaign - an ESO large programme designed to obtai… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.14593v2-abstract-full').style.display = 'inline'; document.getElementById('2407.14593v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2407.14593v2-abstract-full" style="display: none;"> Surveys in the Milky Way and Large Magellanic Cloud revealed that the majority of massive stars will interact with companions during their lives. However, knowledge of the binary properties of massive stars at low metallicity, which approaches the conditions of the Early Universe, remains sparse. We present the Binarity at LOw Metallicity (BLOeM) campaign - an ESO large programme designed to obtain 25 epochs of spectroscopy for 929 massive stars in the SMC - the lowest metallicity conditions in which multiplicity is probed to date (Z = 0.2 Zsun). BLOeM will provide (i) the binary fraction, (ii) the orbital configurations of systems with periods P < 3 yr, (iii) dormant OB+BH binaries, and (iv) a legacy database of physical parameters of massive stars at low metallicity. The stars are observed with the LR02 setup of the giraffe instrument of the Very Large Telescope (3960-4570A, resolving power R=6200; typical signal-to-noise ratio S/N=70-100). This paper utilises the first 9 epochs obtained over a three-month time. We describe the survey and data reduction, perform a spectral classification of the stacked spectra, and construct a Hertzsprung-Russell diagram of the sample via spectral-type and photometric calibrations. The sample covers spectral types from O4 to F5, spanning the effective temperature and luminosity ranges 6.5<Teff/kK<45 and 3.7<log L/Lsun<6.1 and initial masses 8<Mini/Msun<80. It comprises 159 O-type stars, 331 early B-type (B0-3) dwarfs and giants (luminosity classes V-III), 303 early B-type supergiants (II-I), and 136 late-type supergiants. At least 82 stars are Oe/Be stars: 20 O-type and 62 B-type (13% and 11% of the respective samples). In addition, it includes 4 high-mass X-ray binaries, 3 stars resembling luminous blue variables, 2 bloated stripped-star candidates, 2 candidate magnetic stars, and 74 eclipsing binaries. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.14593v2-abstract-full').style.display = 'none'; document.getElementById('2407.14593v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 September, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 19 July, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted to A&A on 27 Aug 2024</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 690, A289 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2407.14216">arXiv:2407.14216</a> <span> [<a href="https://arxiv.org/pdf/2407.14216">pdf</a>, <a href="https://arxiv.org/format/2407.14216">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> X-Shooting ULLYSES: Massive stars at low metallicity VII. Stellar and wind properties of B supergiants in the Small Magellanic Cloud </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Bernini-Peron%2C+M">M. Bernini-Peron</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">V. Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L+M">L. M. Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J+S">J. S. Vink</a>, <a href="/search/astro-ph?searchtype=author&query=Verhamme%2C+O">O. Verhamme</a>, <a href="/search/astro-ph?searchtype=author&query=Najarro%2C+F">F. Najarro</a>, <a href="/search/astro-ph?searchtype=author&query=Josiek%2C+J">J. Josiek</a>, <a href="/search/astro-ph?searchtype=author&query=Brands%2C+S+A">S. A. Brands</a>, <a href="/search/astro-ph?searchtype=author&query=Crowther%2C+P+A">P. A. Crowther</a>, <a href="/search/astro-ph?searchtype=author&query=G%C3%B3mez-Gonz%C3%A1lez%2C+V+M+A">V. M. A. G贸mez-Gonz谩lez</a>, <a href="/search/astro-ph?searchtype=author&query=Gormaz-Matamala%2C+A+C">A. C. Gormaz-Matamala</a>, <a href="/search/astro-ph?searchtype=author&query=Hawcroft%2C+C">C. Hawcroft</a>, <a href="/search/astro-ph?searchtype=author&query=Kuiper%2C+R">R. Kuiper</a>, <a href="/search/astro-ph?searchtype=author&query=Mahy%2C+L">L. Mahy</a>, <a href="/search/astro-ph?searchtype=author&query=Marcolino%2C+W+L+F">W. L. F. Marcolino</a>, <a href="/search/astro-ph?searchtype=author&query=Martins%2C+L+P">L. P. Martins</a>, <a href="/search/astro-ph?searchtype=author&query=Mehner%2C+A">A. Mehner</a>, <a href="/search/astro-ph?searchtype=author&query=Parsons%2C+T+N">T. N. Parsons</a>, <a href="/search/astro-ph?searchtype=author&query=Pauli%2C+D">D. Pauli</a>, <a href="/search/astro-ph?searchtype=author&query=Shenar%2C+T">T. Shenar</a>, <a href="/search/astro-ph?searchtype=author&query=Schootemeijer%2C+A">A. Schootemeijer</a>, <a href="/search/astro-ph?searchtype=author&query=Todt%2C+H">H. Todt</a>, <a href="/search/astro-ph?searchtype=author&query=van+Loon%2C+J+T">J. Th. van Loon</a>, <a href="/search/astro-ph?searchtype=author&query=collaboration%2C+t+X">the XShootU collaboration</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2407.14216v1-abstract-short" style="display: inline;"> Context. B supergiants (BSGs) represent an important connection between the main sequence and more extreme evolutionary stages of massive stars. Additionally, lying toward the cool end of the hot star regime, determining their wind properties is crucial to constrain the evolution and feedback of massive stars as, for instance, they might manifest the bi-stability jump phenomenon. Aims. We undertak… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.14216v1-abstract-full').style.display = 'inline'; document.getElementById('2407.14216v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2407.14216v1-abstract-full" style="display: none;"> Context. B supergiants (BSGs) represent an important connection between the main sequence and more extreme evolutionary stages of massive stars. Additionally, lying toward the cool end of the hot star regime, determining their wind properties is crucial to constrain the evolution and feedback of massive stars as, for instance, they might manifest the bi-stability jump phenomenon. Aims. We undertake a detailed analysis of a representative sample of 18 Small Magellanic Cloud (SMC) BSGs within the ULLYSES and XShootU datasets. Our UV and optical analysis spans BSGs from B0 to B8 - covering the bi-stability jump region. We aim to evaluate their evolutionary status and verify what their wind properties say about the bi-stability jump in a low-metallicity environment. Methods. We used the CMFGEN to model the spectra and photometry (from UV to infrared) of our sample. We compare our results with different evolutionary models, with previous determinations in the literature of OB stars, and with diverging mass-loss recipes at the bi-stability jump. Additionally, we provide the first BSG models in the SMC including X-rays. Results. (i) Within a single-stellar evolution framework, the evolutionary status of early BSGs seem less clear than that of late BSGs, which agree with H-shell burning models. (ii) UV analysis shows evidence that BSGs contain X-rays in their atmospheres, for which we provide constraints. In general, we find higher X-ray luminosity (close to the standard log(L_X/L) ~ -7) for early BSGs. For cooler BSGs, lower values are preferred, log(L_X/L) ~ -8.5. (iii) The obtained mass-loss rates suggest neither a jump nor a monotonic decrease with temperature. Instead, a rather constant trend is observed, which is at odds with the increase found for Galactic BSGs. (iv) The wind velocity behavior with temperature shows a sharp drop at ~19 kK, similar to what is observed for Galactic BSGs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.14216v1-abstract-full').style.display = 'none'; document.getElementById('2407.14216v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 19 July, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">33 pages (23+10)+(22 at Zenodo), 34 figures (21+13)+(21 at Zenodo), 7 tables (3+4)+(1 at Zenodo), accepted for publication</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2407.07983">arXiv:2407.07983</a> <span> [<a href="https://arxiv.org/pdf/2407.07983">pdf</a>, <a href="https://arxiv.org/format/2407.07983">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> New Wolf-Rayet wind yields and nucleosynthesis of Helium stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Higgins%2C+E+R">Erin R. Higgins</a>, <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J+S">Jorick S. Vink</a>, <a href="/search/astro-ph?searchtype=author&query=Hirschi%2C+R">Raphael Hirschi</a>, <a href="/search/astro-ph?searchtype=author&query=Laird%2C+A+M">Alison M. Laird</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2407.07983v1-abstract-short" style="display: inline;"> Strong metallicity-dependent winds dominate the evolution of core He-burning, classical Wolf-Rayet (cWR) stars, which eject both H and He-fusion products such as 14N, 12C, 16O, 19F, 22Ne and 23Na during their evolution. The chemical enrichment from cWRs can be significant. cWR stars are also key sources for neutron production relevant for the weak s-process. We calculate stellar models of cWRs at… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.07983v1-abstract-full').style.display = 'inline'; document.getElementById('2407.07983v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2407.07983v1-abstract-full" style="display: none;"> Strong metallicity-dependent winds dominate the evolution of core He-burning, classical Wolf-Rayet (cWR) stars, which eject both H and He-fusion products such as 14N, 12C, 16O, 19F, 22Ne and 23Na during their evolution. The chemical enrichment from cWRs can be significant. cWR stars are also key sources for neutron production relevant for the weak s-process. We calculate stellar models of cWRs at solar metallicity for a range of initial Helium star masses (12-50M), adopting the recent hydrodynamical wind rates from Sander & Vink (2020). Stellar wind yields are provided for the entire post-main sequence evolution until core O-exhaustion. While literature has previously considered cWRs as a viable source of the radioisotope 26Al, we confirm that negligible 26Al is ejected by cWRs since it has decayed to 26Mg or proton-captured to 27Al. However, in Paper I, Higgins et al. (2023) we showed that very massive stars eject substantial quantities of 26Al, among other elements including N, Ne, and Na, already from the zero-age-main-sequence. Here, we examine the production of 19F and find that even with lower mass-loss rates than previous studies, our cWR models still eject substantial amounts of 19F. We provide central neutron densities (Nn) of a 30M cWR compared with a 32M post-VMS WR and confirm that during core He-burning, cWRs produce a significant number of neutrons for the weak s-process via the 22Ne(alpha,n)25Mg reaction. Finally, we compare our cWR models with observed [Ne/He], [C/He] and [O/He] ratios of Galactic WC and WO stars. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.07983v1-abstract-full').style.display = 'none'; document.getElementById('2407.07983v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 10 July, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in MNRAS. 17 pages, 16 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2407.03137">arXiv:2407.03137</a> <span> [<a href="https://arxiv.org/pdf/2407.03137">pdf</a>, <a href="https://arxiv.org/format/2407.03137">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202449829">10.1051/0004-6361/202449829 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> X-Shooting ULLYSES: Massive stars at low metallicity. IV. Spectral analysis methods and exemplary results for O stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Bouret%2C+J+-">J. -C. Bouret</a>, <a href="/search/astro-ph?searchtype=author&query=Bernini-Peron%2C+M">M. Bernini-Peron</a>, <a href="/search/astro-ph?searchtype=author&query=Puls%2C+J">J. Puls</a>, <a href="/search/astro-ph?searchtype=author&query=Backs%2C+F">F. Backs</a>, <a href="/search/astro-ph?searchtype=author&query=Berlanas%2C+S+R">S. R. Berlanas</a>, <a href="/search/astro-ph?searchtype=author&query=Bestenlehner%2C+J+M">J. M. Bestenlehner</a>, <a href="/search/astro-ph?searchtype=author&query=Brands%2C+S+A">S. A. Brands</a>, <a href="/search/astro-ph?searchtype=author&query=Herrero%2C+A">A. Herrero</a>, <a href="/search/astro-ph?searchtype=author&query=Martins%2C+F">F. Martins</a>, <a href="/search/astro-ph?searchtype=author&query=Maryeva%2C+O">O. Maryeva</a>, <a href="/search/astro-ph?searchtype=author&query=Pauli%2C+D">D. Pauli</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">V. Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Crowther%2C+P+A">P. A. Crowther</a>, <a href="/search/astro-ph?searchtype=author&query=G%C3%B3mez-Gonz%C3%A1lez%2C+V+M+A">V. M. A. G贸mez-Gonz谩lez</a>, <a href="/search/astro-ph?searchtype=author&query=Gormaz-Matamala%2C+A+C">A. C. Gormaz-Matamala</a>, <a href="/search/astro-ph?searchtype=author&query=Hamann%2C+W+-">W. -R. Hamann</a>, <a href="/search/astro-ph?searchtype=author&query=Hillier%2C+D+J">D. J. Hillier</a>, <a href="/search/astro-ph?searchtype=author&query=Kuiper%2C+R">R. Kuiper</a>, <a href="/search/astro-ph?searchtype=author&query=Larkin%2C+C+J+K">C. J. K. Larkin</a>, <a href="/search/astro-ph?searchtype=author&query=Lefever%2C+R+R">R. R. Lefever</a>, <a href="/search/astro-ph?searchtype=author&query=Mehner%2C+A">A. Mehner</a>, <a href="/search/astro-ph?searchtype=author&query=Najarro%2C+F">F. Najarro</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L+M">L. M. Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=Sch%C3%B6sser%2C+E+C">E. C. Sch枚sser</a> , et al. (4 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2407.03137v2-abstract-short" style="display: inline;"> CONTEXT: The spectral analysis of hot, massive stars is a fundamental astrophysical method to obtain their intrinsic properties and their feedback. Quantitative spectroscopy for hot, massive stars requires detailed numerical modeling of the atmosphere and an iterative treatment to obtain the best solution within a given framework. AIMS: We present an overview of different techniques for the quanti… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.03137v2-abstract-full').style.display = 'inline'; document.getElementById('2407.03137v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2407.03137v2-abstract-full" style="display: none;"> CONTEXT: The spectral analysis of hot, massive stars is a fundamental astrophysical method to obtain their intrinsic properties and their feedback. Quantitative spectroscopy for hot, massive stars requires detailed numerical modeling of the atmosphere and an iterative treatment to obtain the best solution within a given framework. AIMS: We present an overview of different techniques for the quantitative spectroscopy of hot stars employed within the X-Shooting ULLYSES collaboration, from grid-based approaches to tailored fits. By performing a blind test, we gain an overview about the similarities and differences of the resulting parameters. Our study aims to provide an overview of the parameter spread caused by different approaches. METHODS: For three different stars from the sample (SMC O5 star AzV 377, LMC O7 star Sk -69 50, and LMC O9 star Sk -66 171), we employ different atmosphere codes (CMFGEN, Fastwind, PoWR) and strategies to determine their best-fitting model. For our analyses, UV and optical spectra are used to derive the properties with some methods relying purely on optical data for comparison. To determine the overall spectral energy distribution, we further employ additional photometry from the literature. RESULTS: Effective temperatures for each of three sample stars agree within 3 kK while the differences in log g can be up to 0.2 dex. Luminosity differences of up to 0.1 dex result from different reddening assumptions, which seem to be larger for the methods employing a genetic algorithm. All sample stars are nitrogen-enriched. CONCLUSIONS: We find a reasonable agreement between the different methods. Tailored fitting tends to be able to minimize discrepancies obtained with more course or automatized treatments. UV spectral data is essential for the determination of realistic wind parameters. For one target (Sk -69 50), we find clear indications of an evolved status. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.03137v2-abstract-full').style.display = 'none'; document.getElementById('2407.03137v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 September, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 3 July, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">19+15 pages, 21+4 figures, accepted version (A&A 689, A30) including language editing, condensed abstract</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 689, A30 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2406.17678">arXiv:2406.17678</a> <span> [<a href="https://arxiv.org/pdf/2406.17678">pdf</a>, <a href="https://arxiv.org/format/2406.17678">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> X-Shooting ULLYSES: Massive Stars at low metallicity VIII. Stellar and wind parameters of newly revealed stripped stars in Be binaries </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">V. Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Pauli%2C+D">D. Pauli</a>, <a href="/search/astro-ph?searchtype=author&query=Klencki%2C+J">J. Klencki</a>, <a href="/search/astro-ph?searchtype=author&query=Backs%2C+F">F. Backs</a>, <a href="/search/astro-ph?searchtype=author&query=Tramper%2C+F">F. Tramper</a>, <a href="/search/astro-ph?searchtype=author&query=Bernini-Peron%2C+M">M. Bernini-Peron</a>, <a href="/search/astro-ph?searchtype=author&query=Crowther%2C+P">P. Crowther</a>, <a href="/search/astro-ph?searchtype=author&query=Hamann%2C+W+-">W. -R. Hamann</a>, <a href="/search/astro-ph?searchtype=author&query=Ignace%2C+R">R. Ignace</a>, <a href="/search/astro-ph?searchtype=author&query=Kuiper%2C+R">R. Kuiper</a>, <a href="/search/astro-ph?searchtype=author&query=Oey%2C+S">S. Oey</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L+M">L. M. Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=Shenar%2C+T">T. Shenar</a>, <a href="/search/astro-ph?searchtype=author&query=Todt%2C+H">H. Todt</a>, <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J+S">J. S. Vink</a>, <a href="/search/astro-ph?searchtype=author&query=Wang%2C+L">L. Wang</a>, <a href="/search/astro-ph?searchtype=author&query=Wofford%2C+A">A. Wofford</a>, <a href="/search/astro-ph?searchtype=author&query=collaboration%2C+t+X">the XShootU collaboration</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2406.17678v1-abstract-short" style="display: inline;"> On the route towards merging neutron stars and stripped-envelope supernovae, binary population synthesis predicts a large number of post-interaction systems with massive stars that have stripped off their outer layers. Yet, observations of such stars in the intermediate-mass regime below the Wolf-Rayet masses are rare. Using X-Shooting ULLYSES (XShootU) data, we discovered three partially stripped… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.17678v1-abstract-full').style.display = 'inline'; document.getElementById('2406.17678v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2406.17678v1-abstract-full" style="display: none;"> On the route towards merging neutron stars and stripped-envelope supernovae, binary population synthesis predicts a large number of post-interaction systems with massive stars that have stripped off their outer layers. Yet, observations of such stars in the intermediate-mass regime below the Wolf-Rayet masses are rare. Using X-Shooting ULLYSES (XShootU) data, we discovered three partially stripped star + Be/Oe binaries in the Magellanic Clouds. We analyzed the UV and optical spectra using the PoWR model atmosphere code by superimposing model spectra corresponding to each component. The estimated current masses of the partially stripped stars fall within the intermediate mass range of 4-8 $M_{\odot}$. These objects are overluminous for their stellar masses, matching core He-burning luminosities. Their Be/Oe secondaries have much higher masses than their stripped primaries (mass ratio > 2). All three partially stripped stars show significant nitrogen enrichment and carbon and oxygen depletion on their surfaces. Additionally, one of our sample stars exhibits significant helium enrichment. Our study provides the first comprehensive determination of the wind parameters of partially stripped stars in the intermediate mass range. The wind mass-loss rates of these stars are found to be on the order of $10^{-7} M_\odot$ yr$^{-1}$, which is over ten times higher than that of OB stars of the same luminosity. Current evolutionary models characterizing this phase typically employ OB or WR mass-loss rates, which underestimate or overestimate stripped stars' mass-loss rates by an order of magnitude. Binary evolution models indicate that the observed primaries had initial masses of 12-17 $M_{\odot}$, making them potential candidates for stripped-envelope supernovae that form neutron stars. If they survive the explosion, these systems may become Be X-ray binaries and later double neutron stars. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.17678v1-abstract-full').style.display = 'none'; document.getElementById('2406.17678v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 June, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in Astronomy & Astrophysics</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2406.13589">arXiv:2406.13589</a> <span> [<a href="https://arxiv.org/pdf/2406.13589">pdf</a>, <a href="https://arxiv.org/format/2406.13589">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> </div> <p class="title is-5 mathjax"> Hydrodynamic simulation of Cygnus OB2: the absence of a cluster wind termination shock </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Vieu%2C+T">Thibault Vieu</a>, <a href="/search/astro-ph?searchtype=author&query=Larkin%2C+C+J+K">Cormac J. K. Larkin</a>, <a href="/search/astro-ph?searchtype=author&query=H%C3%A4rer%2C+L">Lucia H盲rer</a>, <a href="/search/astro-ph?searchtype=author&query=Reville%2C+B">Brian Reville</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">Varsha Ramachandran</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2406.13589v1-abstract-short" style="display: inline;"> We perform a large-scale hydrodynamic simulation of a massive star cluster whose stellar population mimics that of the Cygnus OB2 association. The main-sequence stars are first simulated during 1.6 Myr, until a quasi-stationary state is reached. At this time the three Wolf-Rayet stars observed in Cygnus OB2 are added to the simulation, which continues to 2 Myr. Using a high-resolution grid in the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.13589v1-abstract-full').style.display = 'inline'; document.getElementById('2406.13589v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2406.13589v1-abstract-full" style="display: none;"> We perform a large-scale hydrodynamic simulation of a massive star cluster whose stellar population mimics that of the Cygnus OB2 association. The main-sequence stars are first simulated during 1.6 Myr, until a quasi-stationary state is reached. At this time the three Wolf-Rayet stars observed in Cygnus OB2 are added to the simulation, which continues to 2 Myr. Using a high-resolution grid in the centre of the domain, we can resolve the most massive stars individually, which allows us to probe the kinetic structures at small (parsec) scales. We find that, although the cluster excavates a spherical "superbubble" cavity, the stellar population is too loosely distributed to blow a large-scale cluster wind termination shock, and that collective effects from wind-wind interactions are much less efficient than usually assumed. This challenges our understanding of the ultra-high energy emission observed from the region. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.13589v1-abstract-full').style.display = 'none'; document.getElementById('2406.13589v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 19 June, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">15 pages, 12 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2405.10177">arXiv:2405.10177</a> <span> [<a href="https://arxiv.org/pdf/2405.10177">pdf</a>, <a href="https://arxiv.org/format/2405.10177">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> </div> <p class="title is-5 mathjax"> Peering into the Wolf-Rayet phenomenon through [WO] and [WC] stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Toal%C3%A1%2C+J+A">Jes煤s A. Toal谩</a>, <a href="/search/astro-ph?searchtype=author&query=Todt%2C+H">Helge Todt</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2405.10177v1-abstract-short" style="display: inline;"> Spectroscopic observations have shown for decades that the Wolf-Rayet (WR) phenomenon is ubiquitous among stars with different initial masses. Although much effort to understand the winds from massive WR stars has been presented in the literature, not much has been done for such type of stars in the low-mass range. Here we present an attempt to understand the winds from [WR]-type stars using resul… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.10177v1-abstract-full').style.display = 'inline'; document.getElementById('2405.10177v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2405.10177v1-abstract-full" style="display: none;"> Spectroscopic observations have shown for decades that the Wolf-Rayet (WR) phenomenon is ubiquitous among stars with different initial masses. Although much effort to understand the winds from massive WR stars has been presented in the literature, not much has been done for such type of stars in the low-mass range. Here we present an attempt to understand the winds from [WR]-type stars using results from spectral analyses with the full non-LTE stellar atmosphere code PoWR. These results are put into context with the properties of massive WR stars. We found that WC+[WC] stars and WO+[WO] stars create independent sequences in the mass-loss rate ($\dot{M}$) and modified wind momentum ($D_\mathrm{mom}$) versus luminosity ($L$) diagrams. Our analysis indicates that even when the winds of WR and [WR] stars become optically thin, there is no breakdown of the general mass-loss trend, contrary to the observed ``weak wind phenomenon'' in OB stars. We report that all WR-type stars studied here broadly define single sequences in the wind efficiency ($畏$) versus transformed mass-loss rate ($\dot{M}_\mathrm{t}$), the $\dot{M}_\mathrm{t}$-$T_\mathrm{eff}$ diagram, and the $(L, T_\mathrm{eff}, \dot{M})$ space, which suggest these to be fundamental properties of the WR phenomenon (regardless of the mass range), at least for WR-type stars of the O and C sequences. Our analytical estimations could drive computations of future stellar evolution models for WR-type stars. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.10177v1-abstract-full').style.display = 'none'; document.getElementById('2405.10177v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">11 pages; 5 Figures; 2 Tables; Accepted to MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2405.01267">arXiv:2405.01267</a> <span> [<a href="https://arxiv.org/pdf/2405.01267">pdf</a>, <a href="https://arxiv.org/ps/2405.01267">ps</a>, <a href="https://arxiv.org/format/2405.01267">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> X-Shooting ULLYSES: Massive stars at low metallicity -- V. Effect of metallicity on surface abundances of O stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Martins%2C+F">F. Martins</a>, <a href="/search/astro-ph?searchtype=author&query=Bouret%2C+J+-">J. -C. Bouret</a>, <a href="/search/astro-ph?searchtype=author&query=Hillier%2C+D+J">D. J. Hillier</a>, <a href="/search/astro-ph?searchtype=author&query=Brands%2C+S+A">S. A. Brands</a>, <a href="/search/astro-ph?searchtype=author&query=Crowther%2C+P+A">P. A. Crowther</a>, <a href="/search/astro-ph?searchtype=author&query=Herrero%2C+A">A. Herrero</a>, <a href="/search/astro-ph?searchtype=author&query=Najarro%2C+F">F. Najarro</a>, <a href="/search/astro-ph?searchtype=author&query=Pauli%2C+D">D. Pauli</a>, <a href="/search/astro-ph?searchtype=author&query=Puls%2C+J">J. Puls</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">V. Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J+S">J. S. Vink</a>, <a href="/search/astro-ph?searchtype=author&query=collaboration%2C+t+X">the XshootU collaboration</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2405.01267v1-abstract-short" style="display: inline;"> Massive stars rotate faster, on average, than lower mass stars. Stellar rotation triggers hydrodynamical instabilities which transport angular momentum and chemical species from the core to the surface. Models of high-mass stars that include these processes predict that chemical mixing is stronger at lower metallicity. We aim to test this prediction by comparing the surface abundances of massive s… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.01267v1-abstract-full').style.display = 'inline'; document.getElementById('2405.01267v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2405.01267v1-abstract-full" style="display: none;"> Massive stars rotate faster, on average, than lower mass stars. Stellar rotation triggers hydrodynamical instabilities which transport angular momentum and chemical species from the core to the surface. Models of high-mass stars that include these processes predict that chemical mixing is stronger at lower metallicity. We aim to test this prediction by comparing the surface abundances of massive stars at different metallicities. We performed a spectroscopic analysis of single O stars in the Magellanic Clouds (MCs) based on the ULLYSES and XshootU surveys. We determined the fundamental parameters and helium, carbon, nitrogen, and oxygen surface abundances of 17 LMC and 17 SMC non-supergiant O6-9.5 stars. We complemented these determinations by literature results for additional MCs and also Galactic stars to increase the sample size and metallicity coverage. We investigated the differences in the surface chemical enrichment at different metallicities and compared them with predictions of three sets of evolutionary models. Surface abundances are consistent with CNO-cycle nucleosynthesis. The maximum surface nitrogen enrichment is stronger in MC stars than in Galactic stars. Nitrogen enrichment is also observed in stars with higher surface gravities in the SMC than in the Galaxy. This trend is predicted by models that incorporate chemical transport caused by stellar rotation. The distributions of projected rotational velocities in our samples are likely biased towards slow rotators. A metallicity dependence of surface abundances is demonstrated. The analysis of larger samples with an unbiased distribution of projected rotational velocities is required to better constrain the treatment of chemical mixing and angular momentum transport in massive single and binary stars. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.01267v1-abstract-full').style.display = 'none'; document.getElementById('2405.01267v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">15 pages + appendix. Accepted in Astronomy & Astrophysics</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2405.00085">arXiv:2405.00085</a> <span> [<a href="https://arxiv.org/pdf/2405.00085">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> </div> </div> <p class="title is-5 mathjax"> X-Shooting ULLYSES: Massive Stars at Low Metallicity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J+S">Jorick S. Vink</a>, <a href="/search/astro-ph?searchtype=author&query=Crowther%2C+P">Paul Crowther</a>, <a href="/search/astro-ph?searchtype=author&query=Fullerton%2C+A">Alex Fullerton</a>, <a href="/search/astro-ph?searchtype=author&query=Garcia%2C+M">Miriam Garcia</a>, <a href="/search/astro-ph?searchtype=author&query=Martins%2C+F">Fabrice Martins</a>, <a href="/search/astro-ph?searchtype=author&query=Morrell%2C+N">Nidia Morrell</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L">Lida Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=Louis%2C+N+S">Nicole St. Louis</a>, <a href="/search/astro-ph?searchtype=author&query=ud-Doula%2C+A">Asif ud-Doula</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A">Andreas Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Sana%2C+H">Hugues Sana</a>, <a href="/search/astro-ph?searchtype=author&query=Bouret%2C+J">Jean-Claude Bouret</a>, <a href="/search/astro-ph?searchtype=author&query=Kubatova%2C+B">Brankica Kubatova</a>, <a href="/search/astro-ph?searchtype=author&query=Marchant%2C+P">Pablo Marchant</a>, <a href="/search/astro-ph?searchtype=author&query=Martins%2C+L+P">Lucimara P. Martins</a>, <a href="/search/astro-ph?searchtype=author&query=Wofford%2C+A">Aida Wofford</a>, <a href="/search/astro-ph?searchtype=author&query=van+Loon%2C+J">Jacco van Loon</a>, <a href="/search/astro-ph?searchtype=author&query=Telford%2C+O+G">O. Grace Telford</a>, <a href="/search/astro-ph?searchtype=author&query=G%C3%B6tberg%2C+Y">Ylva G枚tberg</a>, <a href="/search/astro-ph?searchtype=author&query=Bowman%2C+D">Dominic Bowman</a>, <a href="/search/astro-ph?searchtype=author&query=Erba%2C+C">Christi Erba</a>, <a href="/search/astro-ph?searchtype=author&query=Kalari%2C+V">Venu Kalari</a>, <a href="/search/astro-ph?searchtype=author&query=Collaboration%2C+T+X">The XShootU Collaboration</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2405.00085v1-abstract-short" style="display: inline;"> The Hubble Space Telescope has devoted 500 orbits to observing 250 massive stars with low metallicity in the ultraviolet (UV) range within the framework of the ULLYSES program. The X-Shooting ULLYSES (XShootU) project enhances the legacy value of this UV dataset by providing high-quality optical and near-infrared spectra, which are acquired using the wide-wavelength-coverage X-shooter spectrograph… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.00085v1-abstract-full').style.display = 'inline'; document.getElementById('2405.00085v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2405.00085v1-abstract-full" style="display: none;"> The Hubble Space Telescope has devoted 500 orbits to observing 250 massive stars with low metallicity in the ultraviolet (UV) range within the framework of the ULLYSES program. The X-Shooting ULLYSES (XShootU) project enhances the legacy value of this UV dataset by providing high-quality optical and near-infrared spectra, which are acquired using the wide-wavelength-coverage X-shooter spectrograph at ESO's Very Large Telescope. XShootU emphasises the importance of combining UV with optical spectra for the consistent determination of key stellar parameters such as effective temperature, surface gravity, luminosity, abundances, and wind characteristics including mass-loss rates as a function of metallicity. Since uncertainties in these parameters have implications across various branches of astrophysics, the data and modelling generated by the XShootU project are poised to significantly advance our understanding of massive stars at low metallicity. This is particularly crucial for confidently interpreting JWST data of the earliest stellar generations, making XShootU a unique resource for comprehending individual spectra of low-metallicity stars. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.00085v1-abstract-full').style.display = 'none'; document.getElementById('2405.00085v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 30 April, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">6 pages, 6 figures. ESO Large Programme Overview</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> ESO Messenger, 2024 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2404.14488">arXiv:2404.14488</a> <span> [<a href="https://arxiv.org/pdf/2404.14488">pdf</a>, <a href="https://arxiv.org/format/2404.14488">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202449281">10.1051/0004-6361/202449281 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Impact of main-sequence mass loss on the appearance, structure and evolution of Wolf-Rayet stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Josiek%2C+J">Joris Josiek</a>, <a href="/search/astro-ph?searchtype=author&query=Ekstr%C3%B6m%2C+S">Sylvia Ekstr枚m</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2404.14488v1-abstract-short" style="display: inline;"> Stellar winds are one of the most important drivers of massive star evolution and a vital source of chemical, mechanical, and radiative feedback. Despite its significance, mass loss remains a major uncertainty in stellar evolution models. Particularly the interdependencies of different approaches with subsequent evolutionary stages and predicted observable phenomena are far from being systematical… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2404.14488v1-abstract-full').style.display = 'inline'; document.getElementById('2404.14488v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2404.14488v1-abstract-full" style="display: none;"> Stellar winds are one of the most important drivers of massive star evolution and a vital source of chemical, mechanical, and radiative feedback. Despite its significance, mass loss remains a major uncertainty in stellar evolution models. Particularly the interdependencies of different approaches with subsequent evolutionary stages and predicted observable phenomena are far from being systematically understood. In this study, we examine the impact of main sequence mass loss on the structure of massive stars throughout their evolution. A particular focus is placed on the consequences for entering the Wolf-Rayet (WR) regime and the subsequent evolution. Using the Geneva stellar evolution code, we compute grids of single, non-rotating stellar models at solar and Large Magellanic Cloud (LMC) metallicity of initial masses between 20 and 120 solar masses, with two representative prescriptions for high and low main sequence mass loss. We obtain detailed numerical predictions regarding the structure and evolution of massive stars, and infer the role of main sequence mass loss by comparison of the mass-loss rate prescriptions. We present implications for the overall evolutionary trajectory, including the evolution of WR stars, as well as the effect on stellar yields and stellar populations. Mass loss during the main sequence plays an important role due to its ability to affect the sequence and duration of all subsequent phases. We identify several distinct evolutionary paths for massive stars which are significantly influenced by the chosen main sequence mass-loss description. We also discuss the impact of uncertainties other than mass loss on the evolution, in particular those relating to convection. We further demonstrate that not just the total mass loss, but the specific mass-loss history throughout a star's life is a crucial determinant of many aspects, such as the resulting stellar yields. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2404.14488v1-abstract-full').style.display = 'none'; document.getElementById('2404.14488v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 April, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">15 pages, 12 figures, accepted for publication in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 688, A71 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2403.05398">arXiv:2403.05398</a> <span> [<a href="https://arxiv.org/pdf/2403.05398">pdf</a>, <a href="https://arxiv.org/format/2403.05398">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> </div> <p class="title is-5 mathjax"> The Wide-field Spectroscopic Telescope (WST) Science White Paper </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Mainieri%2C+V">Vincenzo Mainieri</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+R+I">Richard I. Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=Brinchmann%2C+J">Jarle Brinchmann</a>, <a href="/search/astro-ph?searchtype=author&query=Cimatti%2C+A">Andrea Cimatti</a>, <a href="/search/astro-ph?searchtype=author&query=Ellis%2C+R+S">Richard S. Ellis</a>, <a href="/search/astro-ph?searchtype=author&query=Hill%2C+V">Vanessa Hill</a>, <a href="/search/astro-ph?searchtype=author&query=Kneib%2C+J">Jean-Paul Kneib</a>, <a href="/search/astro-ph?searchtype=author&query=McLeod%2C+A+F">Anna F. McLeod</a>, <a href="/search/astro-ph?searchtype=author&query=Opitom%2C+C">Cyrielle Opitom</a>, <a href="/search/astro-ph?searchtype=author&query=Roth%2C+M+M">Martin M. Roth</a>, <a href="/search/astro-ph?searchtype=author&query=Sanchez-Saez%2C+P">Paula Sanchez-Saez</a>, <a href="/search/astro-ph?searchtype=author&query=Smiljanic%2C+R">Rodolfo Smiljanic</a>, <a href="/search/astro-ph?searchtype=author&query=Tolstoy%2C+E">Eline Tolstoy</a>, <a href="/search/astro-ph?searchtype=author&query=Bacon%2C+R">Roland Bacon</a>, <a href="/search/astro-ph?searchtype=author&query=Randich%2C+S">Sofia Randich</a>, <a href="/search/astro-ph?searchtype=author&query=Adamo%2C+A">Angela Adamo</a>, <a href="/search/astro-ph?searchtype=author&query=Annibali%2C+F">Francesca Annibali</a>, <a href="/search/astro-ph?searchtype=author&query=Arevalo%2C+P">Patricia Arevalo</a>, <a href="/search/astro-ph?searchtype=author&query=Audard%2C+M">Marc Audard</a>, <a href="/search/astro-ph?searchtype=author&query=Barsanti%2C+S">Stefania Barsanti</a>, <a href="/search/astro-ph?searchtype=author&query=Battaglia%2C+G">Giuseppina Battaglia</a>, <a href="/search/astro-ph?searchtype=author&query=Aran%2C+A+M+B">Amelia M. Bayo Aran</a>, <a href="/search/astro-ph?searchtype=author&query=Belfiore%2C+F">Francesco Belfiore</a>, <a href="/search/astro-ph?searchtype=author&query=Bellazzini%2C+M">Michele Bellazzini</a>, <a href="/search/astro-ph?searchtype=author&query=Bellini%2C+E">Emilio Bellini</a> , et al. (192 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2403.05398v2-abstract-short" style="display: inline;"> The Wide-field Spectroscopic Telescope (WST) is proposed as a new facility dedicated to the efficient delivery of spectroscopic surveys. This white paper summarises the initial concept as well as the corresponding science cases. WST will feature simultaneous operation of a large field-of-view (3 sq. degree), a high multiplex (20,000) multi-object spectrograph (MOS) and a giant 3x3 sq. arcmin integ… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2403.05398v2-abstract-full').style.display = 'inline'; document.getElementById('2403.05398v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2403.05398v2-abstract-full" style="display: none;"> The Wide-field Spectroscopic Telescope (WST) is proposed as a new facility dedicated to the efficient delivery of spectroscopic surveys. This white paper summarises the initial concept as well as the corresponding science cases. WST will feature simultaneous operation of a large field-of-view (3 sq. degree), a high multiplex (20,000) multi-object spectrograph (MOS) and a giant 3x3 sq. arcmin integral field spectrograph (IFS). In scientific capability these requirements place WST far ahead of existing and planned facilities. Given the current investment in deep imaging surveys and noting the diagnostic power of spectroscopy, WST will fill a crucial gap in astronomical capability and work synergistically with future ground and space-based facilities. This white paper shows that WST can address outstanding scientific questions in the areas of cosmology; galaxy assembly, evolution, and enrichment, including our own Milky Way; origin of stars and planets; time domain and multi-messenger astrophysics. WST's uniquely rich dataset will deliver unforeseen discoveries in many of these areas. The WST Science Team (already including more than 500 scientists worldwide) is open to the all astronomical community. To register in the WST Science Team please visit https://www.wstelescope.com/for-scientists/participate <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2403.05398v2-abstract-full').style.display = 'none'; document.getElementById('2403.05398v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 April, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 8 March, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">194 pages, 66 figures. Comments are welcome (wstelescope@gmail.com)</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2402.16987">arXiv:2402.16987</a> <span> [<a href="https://arxiv.org/pdf/2402.16987">pdf</a>, <a href="https://arxiv.org/format/2402.16987">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202347479">10.1051/0004-6361/202347479 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> X-Shooting ULLYSES: Massive Stars at low metallicity II. DR1: Advanced optical data products for the Magellanic Clouds </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Sana%2C+H">H. Sana</a>, <a href="/search/astro-ph?searchtype=author&query=Tramper%2C+F">F. Tramper</a>, <a href="/search/astro-ph?searchtype=author&query=Abdul-Masih%2C+M">M. Abdul-Masih</a>, <a href="/search/astro-ph?searchtype=author&query=Blomme%2C+R">R. Blomme</a>, <a href="/search/astro-ph?searchtype=author&query=Dsilva%2C+K">K. Dsilva</a>, <a href="/search/astro-ph?searchtype=author&query=Maravelias%2C+G">G. Maravelias</a>, <a href="/search/astro-ph?searchtype=author&query=Martins%2C+L">L. Martins</a>, <a href="/search/astro-ph?searchtype=author&query=Mehner%2C+A">A. Mehner</a>, <a href="/search/astro-ph?searchtype=author&query=Wofford%2C+A">A. Wofford</a>, <a href="/search/astro-ph?searchtype=author&query=Banyard%2C+G">G. Banyard</a>, <a href="/search/astro-ph?searchtype=author&query=Barbosa%2C+C+L">C. L. Barbosa</a>, <a href="/search/astro-ph?searchtype=author&query=Bestenlehner%2C+J">J. Bestenlehner</a>, <a href="/search/astro-ph?searchtype=author&query=Hawcroft%2C+C">C. Hawcroft</a>, <a href="/search/astro-ph?searchtype=author&query=Hillier%2C+D+J">D. John Hillier</a>, <a href="/search/astro-ph?searchtype=author&query=Todt%2C+H">H. Todt</a>, <a href="/search/astro-ph?searchtype=author&query=Larkin%2C+C+J+K">C. J. K. Larkin</a>, <a href="/search/astro-ph?searchtype=author&query=Mahy%2C+L">L. Mahy</a>, <a href="/search/astro-ph?searchtype=author&query=Najarro%2C+F">F. Najarro</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">V. Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Ramirez-Tannus%2C+M+C">M. C. Ramirez-Tannus</a>, <a href="/search/astro-ph?searchtype=author&query=Rubio-Diez%2C+M+M">M. M. Rubio-Diez</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Shenar%2C+T">T. Shenar</a>, <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J+S">J. S. Vink</a>, <a href="/search/astro-ph?searchtype=author&query=Backs%2C+F">F. Backs</a> , et al. (12 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2402.16987v1-abstract-short" style="display: inline;"> Using the medium resolution spectrograph X-shooter, spectra of 235 OB and Wolf-Rayet (WR) stars in sub-solar metallicity environments have been secured. [...]This second paper focuses on the optical observations of 232 Magellanic Clouds targets. It describes the uniform reduction of the UVB (300 - 560 nm) and VIS (550 - 1020 nm) XShootU data as well as the preparation of advanced data products [..… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.16987v1-abstract-full').style.display = 'inline'; document.getElementById('2402.16987v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2402.16987v1-abstract-full" style="display: none;"> Using the medium resolution spectrograph X-shooter, spectra of 235 OB and Wolf-Rayet (WR) stars in sub-solar metallicity environments have been secured. [...]This second paper focuses on the optical observations of 232 Magellanic Clouds targets. It describes the uniform reduction of the UVB (300 - 560 nm) and VIS (550 - 1020 nm) XShootU data as well as the preparation of advanced data products [...] . The data reduction of the raw data is based on the ESO CPL X-shooter pipeline. We paid particular attention to the determination of the response curves [...] We implemented slit-loss correction, absolute flux calibration, (semi-)automatic rectification to the continuum, and a correction for telluric lines. The spectra of individual epochs were corrected for the barycentric motion, re-sampled and co-added, and the spectra from the two arms were merged into a single flux calibrated spectrum covering the entire optical range with maximum signal-to-noise ratio. [...] We provide three types of data products: (i) two-dimensional spectra for each UVB and VIS exposure; (ii) one-dimensional UVB and VIS spectra before and after response-correction, as well as after applying various processing, including absolute flux calibration, telluric removal, normalisation and barycentric correction; and (iii) co-added flux-calibrated and rectified spectra over the full optical range, for which all available XShootU exposures were combined. For many of the targets, the final signal-to-noise ratio per resolution element is above 200 in both the UVB and the VIS co-added spectra. The reduced data and advanced scientific data products will be made available to the community upon publication of this paper. [...] <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.16987v1-abstract-full').style.display = 'none'; document.getElementById('2402.16987v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 February, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">22 pages, 19 figures; accepted for publication in Astronomy & Astrophysics. Links to online tables and databases will be included upon publication</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 688, A104 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2402.13230">arXiv:2402.13230</a> <span> [<a href="https://arxiv.org/pdf/2402.13230">pdf</a>, <a href="https://arxiv.org/format/2402.13230">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> Chemical abundances and ionizing mechanisms in the star-forming double-ring of AM 0644-741 using MUSE data </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=G%C3%B3mez-Gonz%C3%A1lez%2C+V+M+A">V. M. A. G贸mez-Gonz谩lez</a>, <a href="/search/astro-ph?searchtype=author&query=Mayya%2C+Y+D">Y. D. Mayya</a>, <a href="/search/astro-ph?searchtype=author&query=Zaragoza-Cardiel%2C+J">J. Zaragoza-Cardiel</a>, <a href="/search/astro-ph?searchtype=author&query=Bruzual%2C+G">G. Bruzual</a>, <a href="/search/astro-ph?searchtype=author&query=Charlot%2C+S">S. Charlot</a>, <a href="/search/astro-ph?searchtype=author&query=Ramos-Larios%2C+G">G. Ramos-Larios</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L+M">L. M. Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Serantes%2C+S+R">S. Reyero Serantes</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2402.13230v1-abstract-short" style="display: inline;"> We present the analysis of archival Very Large Telescope (VLT) Multi-Unit Spectroscopic Explorer (MUSE) observations of 179 HII regions in the star-forming double-ring collisional galaxy AM 0644-741 at 98.6 Mpc. We determined ionic abundances of He, N, O and Fe using the direct method for the brightest H II region (ID 39); we report $\log\rm{(\frac{N}{O})}=-1.3\pm0.2$ and… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.13230v1-abstract-full').style.display = 'inline'; document.getElementById('2402.13230v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2402.13230v1-abstract-full" style="display: none;"> We present the analysis of archival Very Large Telescope (VLT) Multi-Unit Spectroscopic Explorer (MUSE) observations of 179 HII regions in the star-forming double-ring collisional galaxy AM 0644-741 at 98.6 Mpc. We determined ionic abundances of He, N, O and Fe using the direct method for the brightest H II region (ID 39); we report $\log\rm{(\frac{N}{O})}=-1.3\pm0.2$ and $12+\log\rm{(\frac{O}{H})}=8.9\pm0.2$. We also find the so-called `blue-bump', broad He II $\lambda4686$, in the spectrum of this knot of massive star-formation; its luminosity being consistent with the presence of $\sim430$ Wolf-Rayet (WR) stars of the Nitrogen late-type. We determined the O abundances for 137 HII regions using the strong-line method; we report a median value of $12+\log\rm{(\frac{O}{H})}=8.5\pm0.8$. The location of three objects, including the WR complex, coincide with that of an Ultra Luminous X-ray source. Nebular He II is not detected in any H II region. We investigate the physical mechanisms responsible for the observed spectral lines using appropriate diagnostic diagrams and ionization models. We find that the H II regions are being photoionized by star clusters with ages $\sim2.5-20$ Myr and ionization potential $-3.5<$$\log\langle U\rangle$$<-3.0$. In these diagrams, a binary population is needed to reproduce the observables considered in this work. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.13230v1-abstract-full').style.display = 'none'; document.getElementById('2402.13230v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 20 February, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">20 pages. Accepted in MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2401.08971">arXiv:2401.08971</a> <span> [<a href="https://arxiv.org/pdf/2401.08971">pdf</a>, <a href="https://arxiv.org/format/2401.08971">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> Aperture and Resolution Effects on Ultraviolet Star-Forming Properties: Insights from Local Galaxies and Implications for High-Redshift Observations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Clark%2C+I">Ilyse Clark</a>, <a href="/search/astro-ph?searchtype=author&query=Berg%2C+D+A">Danielle A. Berg</a>, <a href="/search/astro-ph?searchtype=author&query=Leitherer%2C+C">Claus Leitherer</a>, <a href="/search/astro-ph?searchtype=author&query=Arellano-Cordova%2C+K+Z">Karla Z. Arellano-Cordova</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2401.08971v1-abstract-short" style="display: inline;"> We present an analysis of the effects of spectral resolution and aperture scales on derived galaxy properties using far-ultraviolet (FUV) spectra of local star-forming galaxies from the International Ultraviolet Explorer (R~250, FOV~10"x20") and Cosmic Origins Spectrograph on the Hubble Space Telescope (R~15,000, FOV~2.5"). Using these spectra, we measured FUV luminosities, spectral slopes, dust a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.08971v1-abstract-full').style.display = 'inline'; document.getElementById('2401.08971v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2401.08971v1-abstract-full" style="display: none;"> We present an analysis of the effects of spectral resolution and aperture scales on derived galaxy properties using far-ultraviolet (FUV) spectra of local star-forming galaxies from the International Ultraviolet Explorer (R~250, FOV~10"x20") and Cosmic Origins Spectrograph on the Hubble Space Telescope (R~15,000, FOV~2.5"). Using these spectra, we measured FUV luminosities, spectral slopes, dust attenuation, and equivalent widths. We find that galaxies with one dominant stellar cluster have FUV properties that are independent of aperture size, while galaxies with multiple bright clusters are sensitive to the total light fraction captured by the aperture. Additionally, we find significant correlations between the strength of stellar and interstellar absorption-lines and metallicity, indicating metallicity-dependent line-driven stellar winds and interstellar macroscopic gas flows shape the stellar and interstellar spectral lines, respectively. The observed line-strength versus metallicity relation of stellar-wind lines agrees with the prediction of population synthesis models for young starbursts. In particular, measurements of the strong stellar CIV 1548,1550 line provide an opportunity to determine stellar abundances as a complement to gas-phase abundances. We provide a relation between the equivalent width of the CIV line and the oxygen abundance of the galaxy. We discuss this relation in terms of the stellar-wind properties of massive stars. As the driving lines in stellar winds are mostly ionized iron species, the CIV line may eventually offer a method to probe alpha-element-to-iron ratios in star-forming galaxies once consistent models with non-solar abundance ratios are available. These results have important implications for the galaxy-scale, low-resolution observations of high-redshift galaxies from JWST (R~100-3,500). <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.08971v1-abstract-full').style.display = 'none'; document.getElementById('2401.08971v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 January, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">This paper has 31 pages total, 11 figures, and a figureset. Accepted for publication in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2401.01240">arXiv:2401.01240</a> <span> [<a href="https://arxiv.org/pdf/2401.01240">pdf</a>, <a href="https://arxiv.org/format/2401.01240">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnras/stad3966">10.1093/mnras/stad3966 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Optically-thick Structure in Early B Type Supergiant Stellar Winds at Low Metallicities </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Parsons%2C+T+N">Timothy N. Parsons</a>, <a href="/search/astro-ph?searchtype=author&query=Prinja%2C+R+K">Raman K. Prinja</a>, <a href="/search/astro-ph?searchtype=author&query=Bernini-Peron%2C+M">Matheus Bernini-Peron</a>, <a href="/search/astro-ph?searchtype=author&query=Fullerton%2C+A+W">Alex W. Fullerton</a>, <a href="/search/astro-ph?searchtype=author&query=Massa%2C+D+L">Derck L. Massa</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L+M">Lidia M. Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=Pauli%2C+D">Daniel Pauli</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Rickard%2C+M+J">Matthew J. Rickard</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2401.01240v1-abstract-short" style="display: inline;"> Accurate determination of mass-loss rates from massive stars is important to understanding stellar and galactic evolution and enrichment of the interstellar medium. Large-scale structure and variability in stellar winds have significant effects on mass-loss rates. Time-series observations provide direct quantification of such variability. Observations of this nature are available for some Galactic… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.01240v1-abstract-full').style.display = 'inline'; document.getElementById('2401.01240v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2401.01240v1-abstract-full" style="display: none;"> Accurate determination of mass-loss rates from massive stars is important to understanding stellar and galactic evolution and enrichment of the interstellar medium. Large-scale structure and variability in stellar winds have significant effects on mass-loss rates. Time-series observations provide direct quantification of such variability. Observations of this nature are available for some Galactic early supergiant stars but not yet for stars in lower metallicity environments such as the Magellanic Clouds. We utilise ultraviolet spectra from the Hubble Space Telescope ULLYSES program to demonstrate that the presence of structure in stellar winds of supergiant stars at low metallicities may be discerned from single-epoch spectra. We find evidence that, for given stellar luminosities and mean stellar wind optical depths, structure is more prevalent at higher metallicities. We confirm, at Large Magellanic Cloud (0.5 Z_solar), Small Magellanic Cloud (0.2 Z_solar) and lower (0.14 -- 0.1 Z_solar) metallicities, earlier Galactic results that there does not appear to be correlation between the degree of structure in stellar winds of massive stars and stellar effective temperature. Similar lack of correlation is found with regard to terminal velocity of stellar winds. Additional and revised values for radial velocities of stars and terminal velocities of stellar winds are presented. Direct evidence of temporal variability, on timescales of several days, in stellar wind at low metallicity is found. We illustrate that narrow absorption components in wind-formed profiles of Galactic OB stellar spectra remain common in early B supergiant spectra at low metallicities, providing means for better constraining hot, massive star mass-loss rates. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.01240v1-abstract-full').style.display = 'none'; document.getElementById('2401.01240v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 January, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">18 pages plus Appendices, 9 figures plus 37 figures in Appendices. Accepted by MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2311.14792">arXiv:2311.14792</a> <span> [<a href="https://arxiv.org/pdf/2311.14792">pdf</a>, <a href="https://arxiv.org/format/2311.14792">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> A soft and transient ultraluminous X-ray source with 6-h modulation in the NGC 300 galaxy </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Sacchi%2C+A">A. Sacchi</a>, <a href="/search/astro-ph?searchtype=author&query=Esposito%2C+P">P. Esposito</a>, <a href="/search/astro-ph?searchtype=author&query=de+Martino%2C+D">D. de Martino</a>, <a href="/search/astro-ph?searchtype=author&query=Soria%2C+R">R. Soria</a>, <a href="/search/astro-ph?searchtype=author&query=Israel%2C+G+L">G. L. Israel</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Sidoli%2C+L">L. Sidoli</a>, <a href="/search/astro-ph?searchtype=author&query=Buckley%2C+D+A+H">D. A. H. Buckley</a>, <a href="/search/astro-ph?searchtype=author&query=Monageng%2C+I+M">I. M. Monageng</a>, <a href="/search/astro-ph?searchtype=author&query=Tiengo%2C+A">A. Tiengo</a>, <a href="/search/astro-ph?searchtype=author&query=Sedda%2C+M+A">M. Arca Sedda</a>, <a href="/search/astro-ph?searchtype=author&query=Pinto%2C+C">C. Pinto</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Stefano%2C+R">R. Di Stefano</a>, <a href="/search/astro-ph?searchtype=author&query=Imbrogno%2C+M">M. Imbrogno</a>, <a href="/search/astro-ph?searchtype=author&query=Carleo%2C+A">A. Carleo</a>, <a href="/search/astro-ph?searchtype=author&query=Rivolta%2C+G">G. Rivolta</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2311.14792v1-abstract-short" style="display: inline;"> We investigate the nature of CXOU J005440.5-374320 (J0054), a peculiar bright ($\sim$$4\times10^{39}$ erg/s) and soft X-ray transient in the spiral galaxy NGC 300 with a 6-hour periodic flux modulation that was detected in a 2014 Chandra observation. Subsequent observations with Chandra and XMM-Newton, as well as a large observational campaign of NGC 300 and its sources performed with the Swift Ne… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.14792v1-abstract-full').style.display = 'inline'; document.getElementById('2311.14792v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2311.14792v1-abstract-full" style="display: none;"> We investigate the nature of CXOU J005440.5-374320 (J0054), a peculiar bright ($\sim$$4\times10^{39}$ erg/s) and soft X-ray transient in the spiral galaxy NGC 300 with a 6-hour periodic flux modulation that was detected in a 2014 Chandra observation. Subsequent observations with Chandra and XMM-Newton, as well as a large observational campaign of NGC 300 and its sources performed with the Swift Neil Gehrels Observatory, showed that this source exhibits recurrent flaring activity: four other outbursts were detected across $\sim$8 years of monitoring. Using data from the Swift/UVOT archive and from the XMM-Newton/OM and Gaia catalogues, we noted the source is likely associated with a bright blue optical/ultraviolet counterpart. This prompted us to perform follow-up observations with the Southern African Large Telescope in December 2019. With the multi-wavelength information at hand, we discuss several possibilities for the nature of J0054. Although none is able to account for the full range of the observed peculiar features, we found that the two most promising scenarios are a stellar-mass compact object in a binary system with a Wolf$-$Rayet star companion, or the recurrent tidal stripping of a stellar object trapped in a system with an intermediate-mass ($\sim1000$ $M_\odot$) black hole. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.14792v1-abstract-full').style.display = 'none'; document.getElementById('2311.14792v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">13 pages, 11 Figures, 3 Tables (the Table in appendix A will be available in the published version). Accepted for publication in A&A</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2309.13113">arXiv:2309.13113</a> <span> [<a href="https://arxiv.org/pdf/2309.13113">pdf</a>, <a href="https://arxiv.org/format/2309.13113">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202346930">10.1051/0004-6361/202346930 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Constraints on the multiplicity of the most massive stars known: R136 a1, a2, a3, and c </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Shenar%2C+T">T. Shenar</a>, <a href="/search/astro-ph?searchtype=author&query=Sana%2C+H">H. Sana</a>, <a href="/search/astro-ph?searchtype=author&query=Crowther%2C+P+A">P. A. Crowther</a>, <a href="/search/astro-ph?searchtype=author&query=Bostroem%2C+K+A">K. A. Bostroem</a>, <a href="/search/astro-ph?searchtype=author&query=Mahy%2C+L">L. Mahy</a>, <a href="/search/astro-ph?searchtype=author&query=Najarro%2C+F">F. Najarro</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L">L. Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2309.13113v1-abstract-short" style="display: inline;"> The most massive stars known to date are R 136 a1, a2, a3, and c within the central cluster R 136a of the Tarantula nebula in the Large Magellanic Cloud (LMC), with reported masses in excess of 150-200$M_\odot$. However, the mass estimation of these stars relies on the assumption that they are single. We collected three epochs of spectroscopy for R 136 a1, a2, a3, and c with the Space Telescope Im… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.13113v1-abstract-full').style.display = 'inline'; document.getElementById('2309.13113v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2309.13113v1-abstract-full" style="display: none;"> The most massive stars known to date are R 136 a1, a2, a3, and c within the central cluster R 136a of the Tarantula nebula in the Large Magellanic Cloud (LMC), with reported masses in excess of 150-200$M_\odot$. However, the mass estimation of these stars relies on the assumption that they are single. We collected three epochs of spectroscopy for R 136 a1, a2, a3, and c with the Space Telescope Imaging Spectrograph (STIS) of the Hubble Space Telescope (HST) in the years 2020-2021 to probe potential radial-velocity (RV) variations. We combine these epochs with an additional HST/STIS observation taken in 2012. We use cross-correlation to quantify the RVs, and establish constraints on possible companions to these stars up to periods of ~10 yr. Objects are classified as binaries when the peak-to-peak RV shifts exceed 50 km/s, and when the RV shift is significant with respect to errors. R 136 a1, a2, and a3 do not satisfy the binary criteria and are thus classified as putatively single, although formal peak-to-peak RV variability on the level 40 km/s is noted for a3. Only R 136 c is classified as binary, in agreement with literature. We can generally rule out massive companions (M2 > ~50 Msun) to R 136 a1, a2, and a3 out to orbital periods of < 1 yr (separations < 5 au) at 95% confidence, or out to tens of years (separations < ~100 au) at 50% confidence. Highly eccentric binaries (e > ~0.9) or twin companions with similar spectra could evade detection down to shorter periods (> ~10 d), though their presence is not supported by the relative X-ray faintness of R 136 a1, a2, and a3. We derive a preliminary orbital solution with a 17.2 d period for the X-ray bright binary R 136 c, though more data are needed to conclusively derive its orbit. Our study supports a lower bound of 150-200 $M_\odot$ on the upper-mass limit at LMC metallicity <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.13113v1-abstract-full').style.display = 'none'; document.getElementById('2309.13113v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 September, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted to A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 679, A36 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2307.05421">arXiv:2307.05421</a> <span> [<a href="https://arxiv.org/pdf/2307.05421">pdf</a>, <a href="https://arxiv.org/format/2307.05421">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202346469">10.1051/0004-6361/202346469 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Clumping and X-Rays in cooler B supergiant stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Bernini-Peron%2C+M">Matheus Bernini-Peron</a>, <a href="/search/astro-ph?searchtype=author&query=Marcolino%2C+W+L+F">Wagner L. F. Marcolino</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Bouret%2C+J">Jean-Claude Bouret</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">Varsha Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Saling%2C+J">Julian Saling</a>, <a href="/search/astro-ph?searchtype=author&query=Schneider%2C+F+R+N">Fabian R. N. Schneider</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L+M">Lidia M. Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=Najarro%2C+F">Francisco Najarro</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2307.05421v2-abstract-short" style="display: inline;"> B supergiants (BSGs) are evolved stars with effective temperatures between 10 to 30 kK and are important to understand massive star evolution. Located on the edge of the line-driven wind regime, the study of their atmospheres is helpful to understand phenomena such as the bi-stability jump. Key UV features of their spectra have so far not been reproduced by models for types later than B1. Here, we… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2307.05421v2-abstract-full').style.display = 'inline'; document.getElementById('2307.05421v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2307.05421v2-abstract-full" style="display: none;"> B supergiants (BSGs) are evolved stars with effective temperatures between 10 to 30 kK and are important to understand massive star evolution. Located on the edge of the line-driven wind regime, the study of their atmospheres is helpful to understand phenomena such as the bi-stability jump. Key UV features of their spectra have so far not been reproduced by models for types later than B1. Here, we aim to remedy this situation via spectral analysis that accounts for wind clumping and X-rays. In addition, we investigate the evolutionary status of our sample stars based on the obtained stellar parameters. We determined parameters via quantitative spectroscopy using CMFGEN and PoWR codes. The models were compared to UV and optical data of four BSGs: HD206165, HD198478, HD53138, and HD164353. We also study the evolutionary status of our sample using GENEC and MESA tracks. When including clumping and X-rays, we find good agreements between synthetic and observed spectra for our sample stars. For the first time, we reproduced key lines in the UV. For that, we require a moderately clumped wind (f_infty > ~0.5). We also infer relative X-ray luminosities of ~10^-7.5 to 10^-8 -- lower than the typical ratio of 10^-7. Moreover, we find a possible mismatch between evolutionary and spectroscopic masses, which could be related to the mass-discrepancy problem present in other OB stars. Our results provide evidence that X-rays and clumping are needed to describe the winds of cool BSGs. However, their winds seem less structured than in earlier type stars. This aligns with observational X-rays and clumping constraints as well as recent hydrodynamical simulations. The BSGs' evolutionary status appears diverse: some objects are potentially post-red supergiants or merger products. The wind parameters provide evidence for a moderate mass-loss rate increase around the bi-stability jump. Abstract abridged <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2307.05421v2-abstract-full').style.display = 'none'; document.getElementById('2307.05421v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 July, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 11 July, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">27 pages, 22 figures, accepted for publication in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 677, A50 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2306.11785">arXiv:2306.11785</a> <span> [<a href="https://arxiv.org/pdf/2306.11785">pdf</a>, <a href="https://arxiv.org/format/2306.11785">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnras/stad1888">10.1093/mnras/stad1888 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Very Massive Stars and Pair-Instability Supernovae: Mass-loss Framework for low Metallicity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Sabhahit%2C+G+N">Gautham N. Sabhahit</a>, <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J+S">Jorick S. Vink</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Higgins%2C+E+R">Erin R. Higgins</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2306.11785v1-abstract-short" style="display: inline;"> Very massive stars (VMS) up to 200-300 $M_\odot$ have been found in the Local Universe. If they would lose little mass they produce intermediate-mass black holes or pair-instability supernovae (PISNe). Until now, VMS modellers have extrapolated mass-loss vs. metallicity ($Z$) exponents from optically-thin winds, resulting in a range of PISN thresholds that might be unrealistically high in $Z$, as… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.11785v1-abstract-full').style.display = 'inline'; document.getElementById('2306.11785v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2306.11785v1-abstract-full" style="display: none;"> Very massive stars (VMS) up to 200-300 $M_\odot$ have been found in the Local Universe. If they would lose little mass they produce intermediate-mass black holes or pair-instability supernovae (PISNe). Until now, VMS modellers have extrapolated mass-loss vs. metallicity ($Z$) exponents from optically-thin winds, resulting in a range of PISN thresholds that might be unrealistically high in $Z$, as VMS develop optically-thick winds. We utilize the transition mass-loss rate of Vink and Gr盲fener (2012) that accurately predicts mass-loss rates of Of/WNh ("slash") stars that characterize the morphological transition from absorption-dominated O-type spectra to emission-dominated WNh spectra. We develop a wind efficiency framework, where optically thin winds transition to enhanced winds, enabling us to study VMS evolution at high redshift where individual stars cannot be resolved. We present a MESA grid covering $Z_\odot/2$ to $Z_\odot/100$. VMS above the transition evolve towards lower luminosity, skipping the cool supergiant phase but directly forming pure He stars at the end of hydrogen burning. Below the transition, VMS evolve as cooler luminous blue variables (LBVs) or yellow hypergiants (YHGs), naturally approaching the Eddington limit. Strong winds in this YHG/LBV regime -- combined with a degeneracy in luminosity -- result in a mass-loss runaway where a decrease in mass increases wind mass loss. Our models indicate an order-of-magnitude lower threshold than usually assumed, at $Z_\odot/20$ due to our mass-loss runaway. While future work on LBV mass loss could affect the PISN threshold, our framework will be critical for establishing definitive answers on the PISN threshold and galactic chemical evolution modelling. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.11785v1-abstract-full').style.display = 'none'; document.getElementById('2306.11785v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 20 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in MNRAS, 18 pages, 8 figures, 2 appendix</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2305.14557">arXiv:2305.14557</a> <span> [<a href="https://arxiv.org/pdf/2305.14557">pdf</a>, <a href="https://arxiv.org/format/2305.14557">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/acd4c5">10.3847/1538-4357/acd4c5 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> From Dust to Nanodust: Resolving Circumstellar Dust from the Colliding-Wind Binary Wolf-Rayet (WR) 140 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Lau%2C+R+M">Ryan M. Lau</a>, <a href="/search/astro-ph?searchtype=author&query=Wang%2C+J">Jason Wang</a>, <a href="/search/astro-ph?searchtype=author&query=Hankins%2C+M+J">Matthew J. Hankins</a>, <a href="/search/astro-ph?searchtype=author&query=Currie%2C+T">Thayne Currie</a>, <a href="/search/astro-ph?searchtype=author&query=Deo%2C+V">Vincent Deo</a>, <a href="/search/astro-ph?searchtype=author&query=Endo%2C+I">Izumi Endo</a>, <a href="/search/astro-ph?searchtype=author&query=Guyon%2C+O">Olivier Guyon</a>, <a href="/search/astro-ph?searchtype=author&query=Han%2C+Y">Yinuo Han</a>, <a href="/search/astro-ph?searchtype=author&query=Jones%2C+A+P">Anthony P. Jones</a>, <a href="/search/astro-ph?searchtype=author&query=Jovanovic%2C+N">Nemanja Jovanovic</a>, <a href="/search/astro-ph?searchtype=author&query=Lozi%2C+J">Julien Lozi</a>, <a href="/search/astro-ph?searchtype=author&query=Moffat%2C+A+F+J">Anthony F. J. Moffat</a>, <a href="/search/astro-ph?searchtype=author&query=Onaka%2C+T">Takashi Onaka</a>, <a href="/search/astro-ph?searchtype=author&query=Ruane%2C+G">Garreth Ruane</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Tinyanont%2C+S">Samaporn Tinyanont</a>, <a href="/search/astro-ph?searchtype=author&query=Tuthill%2C+P+G">Peter G. Tuthill</a>, <a href="/search/astro-ph?searchtype=author&query=Weigelt%2C+G">Gerd Weigelt</a>, <a href="/search/astro-ph?searchtype=author&query=Williams%2C+P+M">Peredur M. Williams</a>, <a href="/search/astro-ph?searchtype=author&query=Vievard%2C+S">Sebastien Vievard</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2305.14557v1-abstract-short" style="display: inline;"> Wolf-Rayet (WR) 140 is the archetypal periodic dust-forming colliding-wind binary that hosts a carbon-rich WR (WC) star and an O-star companion with an orbital period of 7.93 years and an orbital eccentricity of 0.9. Throughout the past several decades, multiple dust-formation episodes from WR 140 have been observed that are linked to the binary orbit and occur near the time of periastron passage.… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.14557v1-abstract-full').style.display = 'inline'; document.getElementById('2305.14557v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2305.14557v1-abstract-full" style="display: none;"> Wolf-Rayet (WR) 140 is the archetypal periodic dust-forming colliding-wind binary that hosts a carbon-rich WR (WC) star and an O-star companion with an orbital period of 7.93 years and an orbital eccentricity of 0.9. Throughout the past several decades, multiple dust-formation episodes from WR 140 have been observed that are linked to the binary orbit and occur near the time of periastron passage. Given its predictable dust-formation episodes, WR 140 presents an ideal astrophysical laboratory for investigating the formation and evolution of dust in the hostile environment around a massive binary system. In this paper, we present near- and mid-infrared (IR) spectroscopic and imaging observations of WR 140 with Subaru/SCExAO+CHARIS, Keck/NIRC2+PyWFS, and Subaru/COMICS taken between 2020 June and Sept that resolve the circumstellar dust emission linked to its most recent dust-formation episode in 2016 Dec. Our spectral energy distribution (SED) analysis of WR 140's resolved circumstellar dust emission reveals the presence of a hot ($T_\mathrm{d}\sim1000$ K) near-IR dust component that is co-spatial with the previously known and cooler ($T_\mathrm{d}\sim500$ K) mid-IR dust component composed of $300-500$ 脜-sized dust grains. We attribute the hot near-IR dust emission to the presence of nano-sized ("nanodust") grains and suggest they were formed from grain-grain collisions or the rotational disruption of the larger grain size population by radiative torques in the strong radiation field from the central binary. Lastly, we speculate on the astrophysical implications of nanodust formation around colliding-wind WC binaries, which may present an early source of carbonaceous nanodust in the interstellar medium. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.14557v1-abstract-full').style.display = 'none'; document.getElementById('2305.14557v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 May, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">21 pages, 8 figures, Accepted for publication in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2305.14262">arXiv:2305.14262</a> <span> [<a href="https://arxiv.org/pdf/2305.14262">pdf</a>, <a href="https://arxiv.org/format/2305.14262">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202346818">10.1051/0004-6361/202346818 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A partially stripped massive star in a Be binary at low metallicity: A missing link towards Be X-ray binaries and double neutron star mergers </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">V. Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Klencki%2C+J">J. Klencki</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Pauli%2C+D">D. Pauli</a>, <a href="/search/astro-ph?searchtype=author&query=Shenar%2C+T">T. Shenar</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L+M">L. M. Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=Hamann%2C+W+-">W. -R. Hamann</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2305.14262v2-abstract-short" style="display: inline;"> Standard binary evolutionary models predict a significant population of core helium-burning stars that lost their hydrogen-rich envelope after mass transfer via Roche-lobe overflow. However, there is a scarcity of observations of such stripped stars in the intermediate mass regime (~1.5 - 8$ M_{\odot}$), which are thought to be prominent progenitors of SN Ib/c. Especially at low metallicity, a sig… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.14262v2-abstract-full').style.display = 'inline'; document.getElementById('2305.14262v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2305.14262v2-abstract-full" style="display: none;"> Standard binary evolutionary models predict a significant population of core helium-burning stars that lost their hydrogen-rich envelope after mass transfer via Roche-lobe overflow. However, there is a scarcity of observations of such stripped stars in the intermediate mass regime (~1.5 - 8$ M_{\odot}$), which are thought to be prominent progenitors of SN Ib/c. Especially at low metallicity, a significant fraction of these stars is expected to be only partially stripped, retaining a significant amount of hydrogen on their surfaces. For the first time, we discovered a partially stripped massive star in a binary with a Be-type companion located in the Small Magellanic Cloud (SMC) using a detailed spectroscopic analysis. The stripped-star nature of the primary is revealed by the extreme CNO abundance pattern and very high luminosity-to-mass ratio, which suggest that the primary is likely shell-hydrogen burning. Our target SMCSGS-FS 69 is the most luminous and most massive system among the known stripped star + Be binaries, with Mstripped ~3$ M_{\odot}$ and MBe ~17$ M_{\odot}$. Binary evolutionary tracks suggest an initial mass of Mini $\gtrsim 12 M_{\odot}$ for the stripped star and predict it to be in a transition phase towards a hot compact He star, which will eventually produce a stripped-envelope supernova. Our target marks the first representative of a so-far missing evolutionary stage in the formation pathway of Be X-ray binaries and double neutron star mergers. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.14262v2-abstract-full').style.display = 'none'; document.getElementById('2305.14262v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 23 May, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication as A&A Letter to the Editor</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 674, L12 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2305.06376">arXiv:2305.06376</a> <span> [<a href="https://arxiv.org/pdf/2305.06376">pdf</a>, <a href="https://arxiv.org/format/2305.06376">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202245650">10.1051/0004-6361/202245650 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> X-Shooting ULLYSES: massive stars at low metallicity. I. Project Description </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J+S">Jorick S. Vink</a>, <a href="/search/astro-ph?searchtype=author&query=Mehner%2C+A">A. Mehner</a>, <a href="/search/astro-ph?searchtype=author&query=Crowther%2C+P+A">P. A. Crowther</a>, <a href="/search/astro-ph?searchtype=author&query=Fullerton%2C+A">A. Fullerton</a>, <a href="/search/astro-ph?searchtype=author&query=Garcia%2C+M">M. Garcia</a>, <a href="/search/astro-ph?searchtype=author&query=Martins%2C+F">F. Martins</a>, <a href="/search/astro-ph?searchtype=author&query=Morrell%2C+N">N. Morrell</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L+M">L. M. Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=St-Louis%2C+N">N. St-Louis</a>, <a href="/search/astro-ph?searchtype=author&query=ud-Doula%2C+A">A. ud-Doula</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Sana%2C+H">H. Sana</a>, <a href="/search/astro-ph?searchtype=author&query=Bouret%2C+J+-">J. -C. Bouret</a>, <a href="/search/astro-ph?searchtype=author&query=Kubatova%2C+B">B. Kubatova</a>, <a href="/search/astro-ph?searchtype=author&query=Marchant%2C+P">P. Marchant</a>, <a href="/search/astro-ph?searchtype=author&query=Martins%2C+L+P">L. P. Martins</a>, <a href="/search/astro-ph?searchtype=author&query=Wofford%2C+A">A. Wofford</a>, <a href="/search/astro-ph?searchtype=author&query=van+Loon%2C+J+T">J. Th. van Loon</a>, <a href="/search/astro-ph?searchtype=author&query=Telford%2C+O+G">O. Grace Telford</a>, <a href="/search/astro-ph?searchtype=author&query=Gotberg%2C+Y">Y. Gotberg</a>, <a href="/search/astro-ph?searchtype=author&query=Bowman%2C+D+M">D. M. Bowman</a>, <a href="/search/astro-ph?searchtype=author&query=Erba%2C+C">C. Erba</a>, <a href="/search/astro-ph?searchtype=author&query=Kalari%2C+V+M">V. M. Kalari</a>, <a href="/search/astro-ph?searchtype=author&query=Abdul-Masih%2C+M">M. Abdul-Masih</a>, <a href="/search/astro-ph?searchtype=author&query=Alkousa%2C+T">T. Alkousa</a> , et al. (56 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2305.06376v3-abstract-short" style="display: inline;"> Observations of individual massive stars, super-luminous supernovae, gamma-ray bursts, and gravitational-wave events involving spectacular black-hole mergers, indicate that the low-metallicity Universe is fundamentally different from our own Galaxy. Many transient phenomena will remain enigmatic until we achieve a firm understanding of the physics and evolution of massive stars at low metallicity… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.06376v3-abstract-full').style.display = 'inline'; document.getElementById('2305.06376v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2305.06376v3-abstract-full" style="display: none;"> Observations of individual massive stars, super-luminous supernovae, gamma-ray bursts, and gravitational-wave events involving spectacular black-hole mergers, indicate that the low-metallicity Universe is fundamentally different from our own Galaxy. Many transient phenomena will remain enigmatic until we achieve a firm understanding of the physics and evolution of massive stars at low metallicity (Z). The Hubble Space Telescope has devoted 500 orbits to observe 250 massive stars at low Z in the ultraviolet (UV) with the COS and STIS spectrographs under the ULLYSES program. The complementary ``X-Shooting ULLYSES'' (XShootU) project provides enhanced legacy value with high-quality optical and near-infrared spectra obtained with the wide-wavelength coverage X-shooter spectrograph at ESO's Very Large Telescope. We present an overview of the XShootU project, showing that combining ULLYSES UV and XShootU optical spectra is critical for the uniform determination of stellar parameters such as effective temperature, surface gravity, luminosity, and abundances, as well as wind properties such as mass-loss rates in function of Z. As uncertainties in stellar and wind parameters percolate into many adjacent areas of Astrophysics, the data and modelling of the XShootU project is expected to be a game-changer for our physical understanding of massive stars at low Z. To be able to confidently interpret James Webb Space Telescope (JWST) spectra of the first stellar generations, the individual spectra of low Z stars need to be understood, which is exactly where XShootU can deliver. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.06376v3-abstract-full').style.display = 'none'; document.getElementById('2305.06376v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 10 May, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted in A&A - 35 Pages, 12 Figures, 4 Tables, 2 Large Tables</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 675, A154 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2303.12165">arXiv:2303.12165</a> <span> [<a href="https://arxiv.org/pdf/2303.12165">pdf</a>, <a href="https://arxiv.org/format/2303.12165">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202245588">10.1051/0004-6361/202245588 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> X-Shooting ULLYSES: Massive stars at low metallicity. III. Terminal wind speeds of ULLYSES massive stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Hawcroft%2C+C">C. Hawcroft</a>, <a href="/search/astro-ph?searchtype=author&query=Sana%2C+H">H. Sana</a>, <a href="/search/astro-ph?searchtype=author&query=Mahy%2C+L">L. Mahy</a>, <a href="/search/astro-ph?searchtype=author&query=Sundqvist%2C+J+O">J. O. Sundqvist</a>, <a href="/search/astro-ph?searchtype=author&query=de+Koter%2C+A">A. de Koter</a>, <a href="/search/astro-ph?searchtype=author&query=Crowther%2C+P+A">P. A. Crowther</a>, <a href="/search/astro-ph?searchtype=author&query=Bestenlehner%2C+J+M">J. M. Bestenlehner</a>, <a href="/search/astro-ph?searchtype=author&query=Brands%2C+S+A">S. A. Brands</a>, <a href="/search/astro-ph?searchtype=author&query=David-Uraz%2C+A">A. David-Uraz</a>, <a href="/search/astro-ph?searchtype=author&query=Decin%2C+L">L. Decin</a>, <a href="/search/astro-ph?searchtype=author&query=Erba%2C+C">C. Erba</a>, <a href="/search/astro-ph?searchtype=author&query=Garcia%2C+M">M. Garcia</a>, <a href="/search/astro-ph?searchtype=author&query=Hamann%2C+W+-">W. -R. Hamann</a>, <a href="/search/astro-ph?searchtype=author&query=Herrero%2C+A">A. Herrero</a>, <a href="/search/astro-ph?searchtype=author&query=Ignace%2C+R">R. Ignace</a>, <a href="/search/astro-ph?searchtype=author&query=Kee%2C+N+D">N. D. Kee</a>, <a href="/search/astro-ph?searchtype=author&query=Kub%C3%A1tov%C3%A1%2C+B">B. Kub谩tov谩</a>, <a href="/search/astro-ph?searchtype=author&query=Lefever%2C+R">R. Lefever</a>, <a href="/search/astro-ph?searchtype=author&query=Moffat%2C+A">A. Moffat</a>, <a href="/search/astro-ph?searchtype=author&query=Najarro%2C+F">F. Najarro</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L">L. Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=Pauli%2C+D">D. Pauli</a>, <a href="/search/astro-ph?searchtype=author&query=Prinja%2C+R">R. Prinja</a>, <a href="/search/astro-ph?searchtype=author&query=Puls%2C+J">J. Puls</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a> , et al. (4 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2303.12165v2-abstract-short" style="display: inline;"> The winds of massive stars have an impact on stellar evolution and on the surrounding medium. The maximum speed reached by these outflows, the terminal wind speed, is a global wind parameter and an essential input for models of stellar atmospheres and feedback. With the arrival of the ULLYSES programme, a legacy UV spectroscopic survey with HST, we have the opportunity to quantify the wind speeds… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.12165v2-abstract-full').style.display = 'inline'; document.getElementById('2303.12165v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2303.12165v2-abstract-full" style="display: none;"> The winds of massive stars have an impact on stellar evolution and on the surrounding medium. The maximum speed reached by these outflows, the terminal wind speed, is a global wind parameter and an essential input for models of stellar atmospheres and feedback. With the arrival of the ULLYSES programme, a legacy UV spectroscopic survey with HST, we have the opportunity to quantify the wind speeds of massive stars at sub-solar metallicity (in the Large and Small Magellanic Clouds, 0.5Z and 0.2Z) at an unprecedented scale. We empirically quantify the wind speeds of a large sample of OB stars, including supergiants, giants, and dwarfs at sub-solar metallicity. Using these measurements, we investigate trends of terminal wind speed with a number of fundamental stellar parameters, namely effective temperature, metallicity, and surface escape velocity. We empirically determined the terminal wind speed for a sample of 149 OB stars in the Magellanic Clouds either by directly measuring the maximum velocity shift of the absorption component of the Civ 1548-1550 line profile, or by fitting synthetic spectra produced using the Sobolev with exact integration method. Stellar parameters were either collected from the literature, obtained using spectral-type calibrations, or predicted from evolutionary models. We find strong trends of terminal wind speed with effective temperature and surface escape speed when the wind is strong enough to cause a saturated P Cygni profile in Civ 1548-1550. We find evidence for a metallicity dependence on the terminal wind speed proportional to Z^0.22+-0.03 when we compared our results to previous Galactic studies. Our results suggest that effective temperature rather than surface escape speed should be used as a straightforward empirical prediction of terminal wind speed and that the observed metallicity dependence is steeper than suggested by earlier works. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.12165v2-abstract-full').style.display = 'none'; document.getElementById('2303.12165v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 March, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 21 March, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">21 pages, 16 figures, 8 tables. Accepted in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 688, A105 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2303.03989">arXiv:2303.03989</a> <span> [<a href="https://arxiv.org/pdf/2303.03989">pdf</a>, <a href="https://arxiv.org/format/2303.03989">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202345881">10.1051/0004-6361/202345881 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Spectroscopic and evolutionary analyses of the binary system AzV 14 outline paths toward the WR stage at low metallicity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Pauli%2C+D">D. Pauli</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L+M">L. M. Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=Hamann%2C+W+-">W. -R. Hamann</a>, <a href="/search/astro-ph?searchtype=author&query=Bowman%2C+D+M">D. M. Bowman</a>, <a href="/search/astro-ph?searchtype=author&query=Todt%2C+H">H. Todt</a>, <a href="/search/astro-ph?searchtype=author&query=Shenar%2C+T">T. Shenar</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Erba%2C+C">C. Erba</a>, <a href="/search/astro-ph?searchtype=author&query=G%C3%B3mez-Gonz%C3%A1lez%2C+V+M+A">V. M. A. G贸mez-Gonz谩lez</a>, <a href="/search/astro-ph?searchtype=author&query=Kehrig%2C+C">C. Kehrig</a>, <a href="/search/astro-ph?searchtype=author&query=Klencki%2C+J">J. Klencki</a>, <a href="/search/astro-ph?searchtype=author&query=Kuiper%2C+R">R. Kuiper</a>, <a href="/search/astro-ph?searchtype=author&query=Mehner%2C+A">A. Mehner</a>, <a href="/search/astro-ph?searchtype=author&query=de+Mink%2C+S+E">S. E. de Mink</a>, <a href="/search/astro-ph?searchtype=author&query=Oey%2C+M+S">M. S. Oey</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">V. Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Schootemeijer%2C+A">A. Schootemeijer</a>, <a href="/search/astro-ph?searchtype=author&query=Serantes%2C+S+R">S. Reyero Serantes</a>, <a href="/search/astro-ph?searchtype=author&query=Wofford%2C+A">A. Wofford</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2303.03989v1-abstract-short" style="display: inline;"> The origin of the observed population of Wolf-Rayet (WR) stars in low-metallicity (low-Z) galaxies, such as the Small Magellanic Cloud (SMC), is not yet understood. Standard, single-star evolutionary models predict that WR stars should stem from very massive O-type star progenitors, but these are very rare. On the other hand, binary evolutionary models predict that WR stars could originate from pr… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.03989v1-abstract-full').style.display = 'inline'; document.getElementById('2303.03989v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2303.03989v1-abstract-full" style="display: none;"> The origin of the observed population of Wolf-Rayet (WR) stars in low-metallicity (low-Z) galaxies, such as the Small Magellanic Cloud (SMC), is not yet understood. Standard, single-star evolutionary models predict that WR stars should stem from very massive O-type star progenitors, but these are very rare. On the other hand, binary evolutionary models predict that WR stars could originate from primary stars in close binaries. We conduct an analysis of the massive O star, AzV 14, to spectroscopically determine its fundamental and stellar wind parameters, which are then used to investigate evolutionary paths from the O-type to the WR stage with stellar evolutionary models. Multi-epoch UV and optical spectra of AzV 14 are analyzed using the non-LTE stellar atmosphere code PoWR. An optical TESS light curve was extracted and analyzed using the PHOEBE code. The obtained parameters are put into an evolutionary context, using the MESA code. AzV 14 is a close binary system consisting of two similar main sequence stars with masses of 32 Msol. Both stars have weak stellar winds with mass-loss rates of log $\dot{M}$ = -7.7. Binary evolutionary models can explain the empirically derived stellar and orbital parameters. The model predicts that the primary will evolve into a WR star with T = 100 kK, while the secondary, which will accrete significant amounts of mass during the first mass transfer phase, will become a cooler WR star with T = 50 kK and are predicted to have compared to other WR stars increased oxygen abundances. This model prediction is supported by a spectroscopic analysis of a WR star in the SMC. We hypothesize that the populations of WR stars in low-Z galaxies may have bimodal temperature distributions. Hotter WR stars might originate from primary stars, while cooler WR stars are the evolutionary descendants of the secondary stars if they accreted a significant amount of mass. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.03989v1-abstract-full').style.display = 'none'; document.getElementById('2303.03989v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 7 March, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">21 pages (13 main body + 8 appendix), 16 figures, 9 tables</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 673, A40 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2302.13964">arXiv:2302.13964</a> <span> [<a href="https://arxiv.org/pdf/2302.13964">pdf</a>, <a href="https://arxiv.org/format/2302.13964">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnras/stad625">10.1093/mnras/stad625 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Exploring the influence of different velocity fields on Wolf-Rayet star spectra </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Lefever%2C+R+R">Roel R. Lefever</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Shenar%2C+T">Tomer Shenar</a>, <a href="/search/astro-ph?searchtype=author&query=Poniatowski%2C+L+G">Luka G. Poniatowski</a>, <a href="/search/astro-ph?searchtype=author&query=Dsilva%2C+K">Karan Dsilva</a>, <a href="/search/astro-ph?searchtype=author&query=Todt%2C+H">Helge Todt</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2302.13964v2-abstract-short" style="display: inline;"> Given their strong stellar winds, Wolf-Rayet (WR) stars exhibit emission line spectra that are predominantly formed in expanding atmospheric layers. The description of the wind velocity field $v(r)$ is therefore a crucial ingredient in the spectral analysis of WR stars, possibly influencing the determination of stellar parameters. In view of this, we perform a systematic study by simulating a sequ… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.13964v2-abstract-full').style.display = 'inline'; document.getElementById('2302.13964v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2302.13964v2-abstract-full" style="display: none;"> Given their strong stellar winds, Wolf-Rayet (WR) stars exhibit emission line spectra that are predominantly formed in expanding atmospheric layers. The description of the wind velocity field $v(r)$ is therefore a crucial ingredient in the spectral analysis of WR stars, possibly influencing the determination of stellar parameters. In view of this, we perform a systematic study by simulating a sequence of WR-star spectra for different temperatures and mass-loss rates using $尾$-type laws with $0.5\leq尾\leq 20$. We quantify the impact of varying $v(r)$ by analysing diagnostic lines and spectral classifications of emergent model spectra computed with the Potsdam Wolf-Rayet (PoWR) code. We additionally cross-check these models with hydrodynamically consistent -- hydro -- model atmospheres. Our analysis confirms that the choice of the $尾$-exponent has a strong impact on WR-star spectra, affecting line widths, line strengths and line profiles. In some parameter regimes, the entire range of WR subtypes could be covered. Comparison with observed WR stars and hydro models revealed that values of $尾\gtrsim 8$ are unlikely to be realized in nature, but a range of $尾$-values needs to be considered in spectral analysis. UV spectroscopy is crucial here to avoid an underestimation of the terminal velocity $v_\infty$. Neither single- nor double-$尾$ descriptions yield an acceptable approximation of the inner wind when compared to hydro models. Instead, we find temperature shifts to lower $T_{2/3}$ when employing a hydro model. Additionally, there are further hints that round-lined profiles seen in several early WN stars are an effect from non-$尾$ velocity laws. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.13964v2-abstract-full').style.display = 'none'; document.getElementById('2302.13964v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 28 February, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 27 February, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">19 pages, 21 figures, accepted for publication in MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2301.13611">arXiv:2301.13611</a> <span> [<a href="https://arxiv.org/pdf/2301.13611">pdf</a>, <a href="https://arxiv.org/format/2301.13611">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1538-3873/acb6b5">10.1088/1538-3873/acb6b5 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Bringing Stellar Evolution & Feedback Together: Summary of proposals from the Lorentz Center Workshop, 2022 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Geen%2C+S">Sam Geen</a>, <a href="/search/astro-ph?searchtype=author&query=Agrawal%2C+P">Poojan Agrawal</a>, <a href="/search/astro-ph?searchtype=author&query=Crowther%2C+P+A">Paul A. Crowther</a>, <a href="/search/astro-ph?searchtype=author&query=Keller%2C+B+W">B. W. Keller</a>, <a href="/search/astro-ph?searchtype=author&query=de+Koter%2C+A">Alex de Koter</a>, <a href="/search/astro-ph?searchtype=author&query=Keszthelyi%2C+Z">Zsolt Keszthelyi</a>, <a href="/search/astro-ph?searchtype=author&query=van+de+Voort%2C+F">Freeke van de Voort</a>, <a href="/search/astro-ph?searchtype=author&query=Ali%2C+A+A">Ahmad A. Ali</a>, <a href="/search/astro-ph?searchtype=author&query=Backs%2C+F">Frank Backs</a>, <a href="/search/astro-ph?searchtype=author&query=Bonne%2C+L">Lars Bonne</a>, <a href="/search/astro-ph?searchtype=author&query=Brugaletta%2C+V">Vittoria Brugaletta</a>, <a href="/search/astro-ph?searchtype=author&query=Derkink%2C+A">Annelotte Derkink</a>, <a href="/search/astro-ph?searchtype=author&query=Ekstr%C3%B6m%2C+S">Sylvia Ekstr枚m</a>, <a href="/search/astro-ph?searchtype=author&query=Fichtner%2C+Y+A">Yvonne A. Fichtner</a>, <a href="/search/astro-ph?searchtype=author&query=Grassitelli%2C+L">Luca Grassitelli</a>, <a href="/search/astro-ph?searchtype=author&query=G%C3%B6tberg%2C+Y">Ylva G枚tberg</a>, <a href="/search/astro-ph?searchtype=author&query=Higgins%2C+E+R">Erin R. Higgins</a>, <a href="/search/astro-ph?searchtype=author&query=Laplace%2C+E">Eva Laplace</a>, <a href="/search/astro-ph?searchtype=author&query=Liow%2C+K+Y">Kong You Liow</a>, <a href="/search/astro-ph?searchtype=author&query=Lorenzo%2C+M">Marta Lorenzo</a>, <a href="/search/astro-ph?searchtype=author&query=McLeod%2C+A+F">Anna F. McLeod</a>, <a href="/search/astro-ph?searchtype=author&query=Meynet%2C+G">Georges Meynet</a>, <a href="/search/astro-ph?searchtype=author&query=Newsome%2C+M">Megan Newsome</a>, <a href="/search/astro-ph?searchtype=author&query=Oliva%2C+G+A">G. Andr茅 Oliva</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">Varsha Ramachandran</a> , et al. (12 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2301.13611v1-abstract-short" style="display: inline;"> Stars strongly impact their environment, and shape structures on all scales throughout the universe, in a process known as ``feedback''. Due to the complexity of both stellar evolution and the physics of larger astrophysical structures, there remain many unanswered questions about how feedback operates, and what we can learn about stars by studying their imprint on the wider universe. In this whit… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.13611v1-abstract-full').style.display = 'inline'; document.getElementById('2301.13611v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2301.13611v1-abstract-full" style="display: none;"> Stars strongly impact their environment, and shape structures on all scales throughout the universe, in a process known as ``feedback''. Due to the complexity of both stellar evolution and the physics of larger astrophysical structures, there remain many unanswered questions about how feedback operates, and what we can learn about stars by studying their imprint on the wider universe. In this white paper, we summarize discussions from the Lorentz Center meeting `Bringing Stellar Evolution and Feedback Together' in April 2022, and identify key areas where further dialogue can bring about radical changes in how we view the relationship between stars and the universe they live in. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.13611v1-abstract-full').style.display = 'none'; document.getElementById('2301.13611v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 31 January, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted to the Publications of the Astronomical Society of the Pacific</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2301.01785">arXiv:2301.01785</a> <span> [<a href="https://arxiv.org/pdf/2301.01785">pdf</a>, <a href="https://arxiv.org/format/2301.01785">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202245110">10.1051/0004-6361/202245110 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The temperature dependency of Wolf-Rayet-type mass loss: An exploratory study for winds launched by the hot iron bump </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Lefever%2C+R+R">R. R. Lefever</a>, <a href="/search/astro-ph?searchtype=author&query=Poniatowski%2C+L+G">L. G. Poniatowski</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">V. Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Sabhahit%2C+G+N">G. N. Sabhahit</a>, <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J+S">J. S. Vink</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2301.01785v1-abstract-short" style="display: inline;"> CONTEXT: The mass loss of He-burning stars, which are partially or completely stripped of their outer hydrogen envelope, is a catalyst of the cosmic matter cycle and decisive ingredient of massive star evolution. Yet, its theoretical fundament is only starting to emerge with major dependencies still to be uncovered. AIMS: A temperature or radius dependence is usually not included in descriptions… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.01785v1-abstract-full').style.display = 'inline'; document.getElementById('2301.01785v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2301.01785v1-abstract-full" style="display: none;"> CONTEXT: The mass loss of He-burning stars, which are partially or completely stripped of their outer hydrogen envelope, is a catalyst of the cosmic matter cycle and decisive ingredient of massive star evolution. Yet, its theoretical fundament is only starting to emerge with major dependencies still to be uncovered. AIMS: A temperature or radius dependence is usually not included in descriptions for the mass loss of classical Wolf-Rayet (cWR) stars, despite being crucial for other hot star wind domains. We thus aim to determine whether such a dependency will also be necessary for a comprehensive description of mass loss in the cWR regime. METHODS: Sequences of dynamically consistent atmosphere models were calculated with the hydrodynamic branch of the PoWR code along the temperature domain, using different choices for luminosity, mass, and surface abundances. For the first time, we allowed nonmonotonic velocity fields when solving the equation of motion. The resulting velocity structures were then interpolated for the comoving-frame radiative transfer, ensuring that the main wind characteristics were preserved. RESULTS: We find a strong dependence of the mass-loss rate with the temperature of the critical/sonic point which mainly reflects the different radii and resulting gravitational accelerations. Moreover, we obtain a relation between the observed effective temperature and the transformed mass-loss rate which seems to be largely independent of the underlying stellar parameters. The relation shifts for different clumping factors in the outer wind. Below a characteristic value of -4.5, the slope of this relation changes and the winds become transparent for He II ionizing photons. CONCLUSIONS: The mass loss of cWR stars is a high-dimensional problem but also shows inherent scalings which can be used to obtain an approximation of the observed effective temperature. (...) <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.01785v1-abstract-full').style.display = 'none'; document.getElementById('2301.01785v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 4 January, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">16 pages + 5 page appendix, 17+9 figures, 3+2 tables. Accepted for publication in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 670, A83 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2211.11457">arXiv:2211.11457</a> <span> [<a href="https://arxiv.org/pdf/2211.11457">pdf</a>, <a href="https://arxiv.org/format/2211.11457">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> The Driving of Hot Star Winds </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2211.11457v1-abstract-short" style="display: inline;"> In the regime of hot stars, winds were not seen as a common thing until the era of UV astronomy. Since we have access to the UV wavelength range, it has become clear that winds are not an exotic phenomenon limited to some special objects, but actually ubiquitous among hot and massive stars. The opacities due to spectral lines are the decisive ingredient that allows hot, massive stars to launch pow… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.11457v1-abstract-full').style.display = 'inline'; document.getElementById('2211.11457v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2211.11457v1-abstract-full" style="display: none;"> In the regime of hot stars, winds were not seen as a common thing until the era of UV astronomy. Since we have access to the UV wavelength range, it has become clear that winds are not an exotic phenomenon limited to some special objects, but actually ubiquitous among hot and massive stars. The opacities due to spectral lines are the decisive ingredient that allows hot, massive stars to launch powerful winds. While the fundamental principles of these so-called line-driven winds have been realized decades ago, their proper quantitative prediction is still a major challenge today. Established theoretical and empirical descriptions have allowed us to make major progress on all astrophysical scales. However, we are now reaching their limitations as we still lack various fundamental insights on the nature of hot star winds, thereby hampering us from drawing deeper conclusions, not least when dealing with stellar or sub-stellar companions. This has spawned a new generation of researchers searching for answers with a yet unprecedented level of detail in observational and new theoretical approaches. In these proceedings, the fundamental principles of driving hot star winds will be briefly reviewed. Starting from the classical CAK theory and its extensions, over Monte Carlo and recent comoving-frame-based simulations, the different methods to describe and model the acceleration of hot star winds will be introduced. The review continues with briefly discussing instabilities as well as qualitative and quantitative insights for OB- and Wolf-Rayet-star winds. Moreover, the challenges of companions and their impact on radiation-driven winds are outlined. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.11457v1-abstract-full').style.display = 'none'; document.getElementById('2211.11457v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 November, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">14 pages, 4 figures, to be published in the Proceedings of the International Astronomical Union for the IAU Symposium 370 "Winds of Stars and Exoplanets" (eds. A.A. Vidotto, L. Fossati, J.S. Vink)</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2211.05424">arXiv:2211.05424</a> <span> [<a href="https://arxiv.org/pdf/2211.05424">pdf</a>, <a href="https://arxiv.org/format/2211.05424">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> Massive Stars in the Far and Extreme Ultraviolet </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2211.05424v1-abstract-short" style="display: inline;"> From the main sequence to their late evolutionary stages, massive stars spend most of their life as hot stars. Due to their high effective temperatures, the maximum of their emitted flux falls into the ultraviolet (UV) regime. Consequently, these stars emit a significant number of photons with energies sufficiently high enough to ionize hydrogen and other elements. As simple as these fundamental c… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.05424v1-abstract-full').style.display = 'inline'; document.getElementById('2211.05424v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2211.05424v1-abstract-full" style="display: none;"> From the main sequence to their late evolutionary stages, massive stars spend most of their life as hot stars. Due to their high effective temperatures, the maximum of their emitted flux falls into the ultraviolet (UV) regime. Consequently, these stars emit a significant number of photons with energies sufficiently high enough to ionize hydrogen and other elements. As simple as these fundamental considerations are, as complex is a realistic estimate of the resulting ionizing fluxes, in particular for energies above 54 eV. Estimating the ionizing flux budget of hot stars requires accurate models of their spectral energy distributions (SEDs), covering in particular the far and extreme UV region. Modern atmosphere models that incorporate the so-called line-blanketing effect, i.e. taking into account the millions of lines from iron and other elements, yield a complex picture, illustrating that the SED of a hot, massive star usually deviates significantly from a blackbody. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.05424v1-abstract-full').style.display = 'none'; document.getElementById('2211.05424v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 10 November, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">3 pages, 4 figures, to be published in the International Astronomical Union Proceedings Series for the IAU GA 2022 (Astronomy in Focus, Focus Meeting 4, ed. Jos茅 Espinosa)</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2209.06043">arXiv:2209.06043</a> <span> [<a href="https://arxiv.org/pdf/2209.06043">pdf</a>, <a href="https://arxiv.org/format/2209.06043">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1017/S1743921322002083">10.1017/S1743921322002083 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Investigating the impact of different velocity fields on the spectral appearance of Wolf-Rayet stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Lefever%2C+R+R">Roel R. Lefever</a>, <a href="/search/astro-ph?searchtype=author&query=Shenar%2C+T">Tomer Shenar</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Poniatowski%2C+L">Luka Poniatowski</a>, <a href="/search/astro-ph?searchtype=author&query=Dsilva%2C+K">Karan Dsilva</a>, <a href="/search/astro-ph?searchtype=author&query=Todt%2C+H">Helge Todt</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2209.06043v1-abstract-short" style="display: inline;"> The emission line spectra of WR stars are often formed completely in the optically thick stellar wind. Hence, any assumption on the wind velocity law in a spectral analysis has a profound impact on the determination of the stellar parameters. By comparing Potsdam Wolf-Rayet (PoWR) model spectra calculated with different $尾$ laws, we show that the velocity field heavily influences the spectra: by u… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.06043v1-abstract-full').style.display = 'inline'; document.getElementById('2209.06043v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2209.06043v1-abstract-full" style="display: none;"> The emission line spectra of WR stars are often formed completely in the optically thick stellar wind. Hence, any assumption on the wind velocity law in a spectral analysis has a profound impact on the determination of the stellar parameters. By comparing Potsdam Wolf-Rayet (PoWR) model spectra calculated with different $尾$ laws, we show that the velocity field heavily influences the spectra: by using the appropriate $尾$ laws, the entire range of late and early types can be covered with the same stellar model. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.06043v1-abstract-full').style.display = 'none'; document.getElementById('2209.06043v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 September, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">2 pages, 1 figure, to be published in the Proceedings of the International Astronomical Union for the IAU Symposium 361 "Massive Stars Near and Far"</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2209.00667">arXiv:2209.00667</a> <span> [<a href="https://arxiv.org/pdf/2209.00667">pdf</a>, <a href="https://arxiv.org/format/2209.00667">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnras/stac2485">10.1093/mnras/stac2485 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The hydrogen clock to infer the upper stellar mass </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Higgins%2C+E+R">Erin R. Higgins</a>, <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J+S">Jorick S. Vink</a>, <a href="/search/astro-ph?searchtype=author&query=Sabhahit%2C+G+N">Gautham N. Sabhahit</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2209.00667v1-abstract-short" style="display: inline;"> The most massive stars dominate the chemical enrichment, mechanical and radiative feedback, and energy budget of their host environments. Yet how massive stars initially form and how they evolve throughout their lives is ambiguous. The mass loss of the most massive stars remains a key unknown in stellar physics, with consequences for stellar feedback and populations. In this work, we compare grids… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.00667v1-abstract-full').style.display = 'inline'; document.getElementById('2209.00667v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2209.00667v1-abstract-full" style="display: none;"> The most massive stars dominate the chemical enrichment, mechanical and radiative feedback, and energy budget of their host environments. Yet how massive stars initially form and how they evolve throughout their lives is ambiguous. The mass loss of the most massive stars remains a key unknown in stellar physics, with consequences for stellar feedback and populations. In this work, we compare grids of very massive star (VMS) models with masses ranging from 80-1000Msun, for a range of input physics. We include enhanced winds close to the Eddington limit as a comparison to standard O-star winds, with consequences for present-day observations of ~50-100Msun stars. We probe the relevant surface H abundances (Xs) to determine the key traits of VMS evolution compared to O stars. We find fundamental differences in the behaviour of our models with the enhanced-wind prescription, with a convergence on the stellar mass at 1.6 Myr, regardless of the initial mass. It turns out that Xs is an important tool in deciphering the initial mass due to the chemically homogeneous nature of VMS above a mass threshold. We use Xs to break the degeneracy of the initial masses of both components of a detached binary, and a sample of WNh stars in the Tarantula nebula. We find that for some objects, the initial masses are unrestricted and, as such, even initial masses of the order 1000Msun are not excluded. Coupled with the mass turnover at 1.6 Myr, Xs can be used as a 'clock' to determine the upper stellar mass. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.00667v1-abstract-full').style.display = 'none'; document.getElementById('2209.00667v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 September, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in MNRAS, 14 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2209.00312">arXiv:2209.00312</a> <span> [<a href="https://arxiv.org/pdf/2209.00312">pdf</a>, <a href="https://arxiv.org/format/2209.00312">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1017/S1743921322002071">10.1017/S1743921322002071 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The enigmatic winds of Wolf-Rayet stars: Results from dynamically consistent atmosphere modelling </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2209.00312v1-abstract-short" style="display: inline;"> Line-driven stellar winds are ubiquitous among hot massive stars. In some cases they can become so strong, that the whole star is cloaked by an optically thick wind. The strong outflow gives rise to large emission lines, defining the class of so-called Wolf-Rayet (WR) stars. While being major players in the evolution of massive stars, the formation of heavy black holes,and the distribution of elem… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.00312v1-abstract-full').style.display = 'inline'; document.getElementById('2209.00312v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2209.00312v1-abstract-full" style="display: none;"> Line-driven stellar winds are ubiquitous among hot massive stars. In some cases they can become so strong, that the whole star is cloaked by an optically thick wind. The strong outflow gives rise to large emission lines, defining the class of so-called Wolf-Rayet (WR) stars. While being major players in the evolution of massive stars, the formation of heavy black holes,and the distribution of elements, the occurrence and nature of WR winds is still quite enigmatic. A promising instrument towards a better theoretical understanding are stellar atmospheres allowing for a consistent inclusion of the hydrodynamics. By coupling stellar and wind parameters and the inclusion of a detailed non-LTE radiative transfer, they allow us to go beneath the observable layers and study the onset of WR-type winds. Establishing larger sets of models, we were able to make ground-breaking progress by identifying trends with mass and metallicity that deviate significantly from present empirical descriptions. Our modelling efforts reveal a complex picture for WR-type winds with strong, non-linear dependencies. Besides covering metallicity and mass, we further identify surface hydrogen as an important ingredient to retain WR-type mass loss at lower metallicity. Here, we present a summary of recent insights on the nature and onset of WR-type winds in massive stars including the consequences for stellar evolution, remaining open questions, and current efforts to overcome them. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.00312v1-abstract-full').style.display = 'none'; document.getElementById('2209.00312v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 September, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">6 pages, 3 figures, to be published in the Proceedings of the International Astronomical Union for the IAU Symposium 361 "Massive Stars Near and Far" (eds. N. St-Louis, J.S. Vink, J. Mackey)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Proc. IAU 18 (2022) 473-478 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2208.07773">arXiv:2208.07773</a> <span> [<a href="https://arxiv.org/pdf/2208.07773">pdf</a>, <a href="https://arxiv.org/format/2208.07773">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202243683">10.1051/0004-6361/202243683 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Phase-resolved spectroscopic analysis of the eclipsing black hole X-ray binary M33 X-7: System properties, accretion, and evolution </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">V. Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L+M">L. M. Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=Hamann%2C+W+-">W. -R. Hamann</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Todt%2C+H">H. Todt</a>, <a href="/search/astro-ph?searchtype=author&query=Pauli%2C+D">D. Pauli</a>, <a href="/search/astro-ph?searchtype=author&query=Shenar%2C+T">T. Shenar</a>, <a href="/search/astro-ph?searchtype=author&query=Torrej%C3%B3n%2C+J+M">J. M. Torrej贸n</a>, <a href="/search/astro-ph?searchtype=author&query=Postnov%2C+K+A">K. A. Postnov</a>, <a href="/search/astro-ph?searchtype=author&query=Blondin%2C+J+M">J. M. Blondin</a>, <a href="/search/astro-ph?searchtype=author&query=Bozzo%2C+E">E. Bozzo</a>, <a href="/search/astro-ph?searchtype=author&query=Hainich%2C+R">R. Hainich</a>, <a href="/search/astro-ph?searchtype=author&query=Massa%2C+D">D. Massa</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2208.07773v1-abstract-short" style="display: inline;"> M33 X-7 is the only known eclipsing black hole high mass X-ray binary. The system is reported to contain a very massive O supergiant donor and a massive black hole in a short orbit. The high X-ray luminosity and its location in the metal-poor galaxy M33 make it a unique laboratory for studying the winds of metal-poor donor stars with black hole companions and it helps us to understand the potentia… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2208.07773v1-abstract-full').style.display = 'inline'; document.getElementById('2208.07773v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2208.07773v1-abstract-full" style="display: none;"> M33 X-7 is the only known eclipsing black hole high mass X-ray binary. The system is reported to contain a very massive O supergiant donor and a massive black hole in a short orbit. The high X-ray luminosity and its location in the metal-poor galaxy M33 make it a unique laboratory for studying the winds of metal-poor donor stars with black hole companions and it helps us to understand the potential progenitors of black hole mergers. Using phase-resolved simultaneous HST- and XMM-Newton-observations, we traced the interaction of the stellar wind with the black hole. Our comprehensive spectroscopic investigation of the donor star (X-ray+UV+optical) yields new stellar and wind parameters for the system that differs significantly from previous estimates. In particular, the masses of the components are considerably reduced to 38 for the O-star donor and 11.4 for the black hole. The O giant is overfilling its Roche lobe and shows surface He enrichment. The donor shows a densely clumped wind with a mass-loss rate that matches theoretical predictions. We investigated the wind-driving contributions from different ions and the changes in the ionization structure due to X-ray illumination. Toward the black hole, the wind is strongly quenched due to strong X-ray illumination. For this system, the standard wind-fed accretion scenario alone cannot explain the observed X-ray luminosity, pointing toward an additional mass overflow, which is in line with our acceleration calculations. The X-ray photoionization creates an He II emission region emitting $10^{47}$ ph/s. We computed binary evolutionary tracks for the system using MESA. Currently, the system is transitioning toward an unstable mass transfer phase, resulting in a common envelope of the black hole and donor. Since the mass ratio is q~3.3 and the period is short, the system is unlikely to survive the common envelope, but will rather merge. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2208.07773v1-abstract-full').style.display = 'none'; document.getElementById('2208.07773v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 August, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in Astronomy & Astrophysics</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 667, A77 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2207.09333">arXiv:2207.09333</a> <span> [<a href="https://arxiv.org/pdf/2207.09333">pdf</a>, <a href="https://arxiv.org/format/2207.09333">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202243281">10.1051/0004-6361/202243281 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Stellar wind properties of the nearly complete sample of O stars in the low metallicity young star cluster NGC346 in the SMC galaxy </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Rickard%2C+M+J">M. J. Rickard</a>, <a href="/search/astro-ph?searchtype=author&query=Hainich%2C+R">R. Hainich</a>, <a href="/search/astro-ph?searchtype=author&query=Hamann%2C+W+-">W. -R. Hamann</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L+M">L. M. Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=Prinja%2C+R+K">R. K. Prinja</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">V. Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Pauli%2C+D">D. Pauli</a>, <a href="/search/astro-ph?searchtype=author&query=Todt%2C+H">H. Todt</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+C+C">A. C. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Shenar%2C+T">T. Shenar</a>, <a href="/search/astro-ph?searchtype=author&query=Chu%2C+Y+-">Y. -H. Chu</a>, <a href="/search/astro-ph?searchtype=author&query=Gallagher%2C+J+S">J. S. Gallagher III</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2207.09333v1-abstract-short" style="display: inline;"> Massive stars are among the main cosmic engines driving the evolution of star-forming galaxies. Their powerful ionising radiation and stellar winds inject a large amount of energy in the interstellar medium. Furthermore, mass-loss ($\dot{M}$) through radiatively driven winds plays a key role in the evolution of massive stars. Even so, the wind mass-loss prescriptions used in stellar evolution mode… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2207.09333v1-abstract-full').style.display = 'inline'; document.getElementById('2207.09333v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2207.09333v1-abstract-full" style="display: none;"> Massive stars are among the main cosmic engines driving the evolution of star-forming galaxies. Their powerful ionising radiation and stellar winds inject a large amount of energy in the interstellar medium. Furthermore, mass-loss ($\dot{M}$) through radiatively driven winds plays a key role in the evolution of massive stars. Even so, the wind mass-loss prescriptions used in stellar evolution models, population synthesis, and stellar feedback models often disagree with mass-loss rates empirically measured from the UV spectra of low metallicity massive stars. The most massive young star cluster in the low metallicity Small Magellanic Cloud galaxy is NGC346. This cluster contains more than half of all O stars discovered in this galaxy so far. A similar age, metallicity ($Z$), and extinction, the O stars in the NGC346 cluster are uniquely suited for a comparative study of stellar winds in O stars of different subtypes. We aim to use a sample of O stars within NGC346 to study stellar winds at low metallicity. We mapped the central 1" of NGC346 with the long-slit UV observations performed by the Space Telescope Imaging Spectrograph (STIS) on board of the {\em Hubble Space Telescope} and complemented these new datasets with archival observations. Multi-epoch observations allowed for the detection of wind variability. The UV dataset was supplemented by optical spectroscopy and photometry. The resulting spectra were analysed using a non-local thermal equilibrium model atmosphere code (PoWR) to determine wind parameters and ionising fluxes. The effective mapping technique allowed us to obtain a mosaic of almost the full extent of the cluster and resolve stars in its core. Among hundreds of extracted stellar spectra, 21 belong to O stars. Nine of them are classified as O stars for the first time. We analyse, in detail, the UV spectra of 19 O stars... (continued) <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2207.09333v1-abstract-full').style.display = 'none'; document.getElementById('2207.09333v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 19 July, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">33 pages, 40 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 666, A189 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2205.09125">arXiv:2205.09125</a> <span> [<a href="https://arxiv.org/pdf/2205.09125">pdf</a>, <a href="https://arxiv.org/format/2205.09125">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnras/stac1410">10.1093/mnras/stac1410 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Mass-loss implementation and temperature evolution of very massive stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Sabhahit%2C+G+N">Gautham N. Sabhahit</a>, <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J+S">Jorick S. Vink</a>, <a href="/search/astro-ph?searchtype=author&query=Higgins%2C+E+R">Erin R. Higgins</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2205.09125v2-abstract-short" style="display: inline;"> Very massive stars (VMS) dominate the physics of young clusters due to their ionising radiation and extreme stellar winds. It is these winds that determine their lifepaths until expiration. Observations in the Arches cluster show that VMS all have similar temperatures. The VLT-Flames Tarantula survey analysed VMS in the 30 Dor region of the LMC also finding a narrow range of temperatures, albeit a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.09125v2-abstract-full').style.display = 'inline'; document.getElementById('2205.09125v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2205.09125v2-abstract-full" style="display: none;"> Very massive stars (VMS) dominate the physics of young clusters due to their ionising radiation and extreme stellar winds. It is these winds that determine their lifepaths until expiration. Observations in the Arches cluster show that VMS all have similar temperatures. The VLT-Flames Tarantula survey analysed VMS in the 30 Dor region of the LMC also finding a narrow range of temperatures, albeit at higher values - likely a metallicity effect. Using MESA, we study the main-sequence evolution of VMS with a new mass-loss recipe that switches from optically-thin O-star winds to optically-thick Wolf-Rayet type winds through the model-independent transition mass-loss rate of Vink & Gr盲fener. We examine the temperature evolution of VMS with mass loss that scales with the luminosity-over-mass (L/M) ratio and the Eddington parameter ($螕_{\rm e}$), assessing the relevance of the surface hydrogen (H) abundance which sets the number of free electrons. We present grids of VMS models at Galactic and LMC metallicity and compare our temperature predictions with empirical results. Models with a steep $螕_{\rm e}$-dependence evolve horizontally in the Hertzsprung-Russel (HR) diagram at nearly constant luminosities, requiring a delicate and unlikely balance between envelope inflation and enhanced mass loss over the entire VMS mass range. By contrast, models with a steep L/M-dependent mass loss are shown to evolve vertically in the HR-diagram at nearly constant Teff, naturally reproducing the narrow range of observed temperatures, as well as the correct trend with metallicity. This distinct behavior of a steeply dropping luminosity is a self-regulatory mechanism that keeps temperatures constant during evolution in the HR-diagram. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.09125v2-abstract-full').style.display = 'none'; document.getElementById('2205.09125v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 July, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 18 May, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in MNRAS. 18 pages, 16 figures, 1 appendix</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2202.04671">arXiv:2202.04671</a> <span> [<a href="https://arxiv.org/pdf/2202.04671">pdf</a>, <a href="https://arxiv.org/format/2202.04671">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1017/S1743921322000400">10.1017/S1743921322000400 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The origin and impact of Wolf-Rayet-type mass loss </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J+S">Jorick S. Vink</a>, <a href="/search/astro-ph?searchtype=author&query=Higgins%2C+E+R">Erin R. Higgins</a>, <a href="/search/astro-ph?searchtype=author&query=Shenar%2C+T">Tomer Shenar</a>, <a href="/search/astro-ph?searchtype=author&query=Hamann%2C+W">Wolf-Rainer Hamann</a>, <a href="/search/astro-ph?searchtype=author&query=Todt%2C+H">Helge Todt</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2202.04671v1-abstract-short" style="display: inline;"> Classical Wolf-Rayet (WR) stars mark an important stage in the late evolution of massive stars. As hydrogen-poor massive stars, these objects have lost their outer layers, while still losing further mass through strong winds indicated by their prominent emission line spectra. Wolf-Rayet stars have been detected in a variety of different galaxies. Their strong winds are a major ingredient of stella… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.04671v1-abstract-full').style.display = 'inline'; document.getElementById('2202.04671v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2202.04671v1-abstract-full" style="display: none;"> Classical Wolf-Rayet (WR) stars mark an important stage in the late evolution of massive stars. As hydrogen-poor massive stars, these objects have lost their outer layers, while still losing further mass through strong winds indicated by their prominent emission line spectra. Wolf-Rayet stars have been detected in a variety of different galaxies. Their strong winds are a major ingredient of stellar evolution and population synthesis models. Yet, a coherent theoretical picture of their strong mass-loss is only starting to emerge. In particular, the occurrence of WR stars as a function of metallicity (Z) is still far from being understood. To uncover the nature of the complex and dense winds of Wolf-Rayet stars, we employ a new generation of model atmospheres including a consistent solution of the wind hydrodynamics in an expanding non-LTE situation. With this technique, we can dissect the ingredients driving the wind and predict the resulting mass-loss for hydrogen-depleted massive stars. Our modelling efforts reveal a complex picture with strong, non-linear dependencies on the luminosity-to-mass ratio and Z with a steep, but not totally abrupt onset for WR-type winds in helium stars. With our findings, we provide a theoretical motivation for a population of helium stars at low Z, which cannot be detected via WR-type spectral features. Our study of massive He-star atmosphere models yields the very first mass-loss recipe derived from first principles in this regime. Implementing our first findings in stellar evolution models, we demonstrate how traditional approaches tend to overpredict WR-type mass loss in the young Universe. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.04671v1-abstract-full').style.display = 'none'; document.getElementById('2202.04671v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 9 February, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">6 pages, 3 figures, to appear in the proceedings of IAUS 366 "The Origin of Outflows in Evolved Stars"</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2201.12364">arXiv:2201.12364</a> <span> [<a href="https://arxiv.org/pdf/2201.12364">pdf</a>, <a href="https://arxiv.org/ps/2201.12364">ps</a>, <a href="https://arxiv.org/format/2201.12364">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1017/S1743921322000631">10.1017/S1743921322000631 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Link between Hot and Cool Outflows </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J+S">Jorick S. Vink</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Higgins%2C+E+R">E. R. Higgins</a>, <a href="/search/astro-ph?searchtype=author&query=Sabhahit%2C+G+N">G. N. Sabhahit</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2201.12364v2-abstract-short" style="display: inline;"> The link between hot and cool stellar outflows is shown to be critical for correctly predicting the masses of the most massive black holes (BHs) below the so-called pair-instability supernova (PISN) mass gap. Gravitational Wave (GW) event 190521 allegedly hosted an "impossibly" heavy BH of 85 Solar Masses. Here we show how our increased knowledge of both metallicity Z and temperature dependent mas… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.12364v2-abstract-full').style.display = 'inline'; document.getElementById('2201.12364v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2201.12364v2-abstract-full" style="display: none;"> The link between hot and cool stellar outflows is shown to be critical for correctly predicting the masses of the most massive black holes (BHs) below the so-called pair-instability supernova (PISN) mass gap. Gravitational Wave (GW) event 190521 allegedly hosted an "impossibly" heavy BH of 85 Solar Masses. Here we show how our increased knowledge of both metallicity Z and temperature dependent mass loss is critical for our evolutionary scenario of a low-Z blue supergiant (BSG) progenitor of an initially approx 100 Solar Masses star to work. We show using MESA stellar evolution modelling experiments that as long as we can keep such stars above 8000 K such low-Z BSGs can avoid strong winds, and keep a very large envelope mass intact before core collapse. This naturally leads to the Cosmic Time dependent maximum BH function below the PISN gap. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.12364v2-abstract-full').style.display = 'none'; document.getElementById('2201.12364v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 11 February, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 28 January, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">6 pages, 4 figures. Talk in IAUS 366</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2201.09148">arXiv:2201.09148</a> <span> [<a href="https://arxiv.org/pdf/2201.09148">pdf</a>, <a href="https://arxiv.org/format/2201.09148">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202141738">10.1051/0004-6361/202141738 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The earliest O-type eclipsing binary in the Small Magellanic Cloud, AzV 476: A comprehensive analysis reveals surprisingly low stellar masses </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Pauli%2C+D">D. Pauli</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L+M">L. M. Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=Hamann%2C+W+-">W. -R. Hamann</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">V. Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Todt%2C+H">H. Todt</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Shenar%2C+T">T. Shenar</a>, <a href="/search/astro-ph?searchtype=author&query=Rickard%2C+M">M. Rickard</a>, <a href="/search/astro-ph?searchtype=author&query=Apell%C3%A1niz%2C+J+M">J. Ma铆z Apell谩niz</a>, <a href="/search/astro-ph?searchtype=author&query=Prinja%2C+R">R. Prinja</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2201.09148v1-abstract-short" style="display: inline;"> Massive stars at low metallicity are among the main feedback agents in the early Universe and in present-day star forming galaxies. When in binaries, these stars are potential progenitors of gravitational-wave events. Knowledge of stellar masses is a prerequisite to understanding evolution and feedback of low-metallicity massive stars. Using abundant spectroscopic and photometric measurements of a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.09148v1-abstract-full').style.display = 'inline'; document.getElementById('2201.09148v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2201.09148v1-abstract-full" style="display: none;"> Massive stars at low metallicity are among the main feedback agents in the early Universe and in present-day star forming galaxies. When in binaries, these stars are potential progenitors of gravitational-wave events. Knowledge of stellar masses is a prerequisite to understanding evolution and feedback of low-metallicity massive stars. Using abundant spectroscopic and photometric measurements of an outstandingly bright eclipsing binary, we compare its dynamic, spectroscopic, and evolutionary mass estimates and develop a binary evolution scenario. We comprehensively studied the eclipsing binary system, AzV 476, in the Small Magellanic Cloud. The light curve and radial velocities were analyzed to obtain the orbital parameters. The photometric and spectroscopic data in the UV and optical were analyzed using the Potsdam Wolf-Rayet model atmospheres. The obtained results are interpreted using binary-evolution tracks. AzV 476 consists of an O4IV-III((f))p primary and an O9.5:Vn secondary. Both components have similar current masses (~20 M$_{\odot}$) obtained from both the orbital and spectroscopic analysis. The wind mass-loss rate of log($\dot{M}$/(M$_{\odot}$/yr))=-6.2 of the primary is a factor of ten higher than a recent empirical prescription for single O stars in the SMC. Only close-binary evolution with mass transfer can reproduce the current stellar and orbital parameters. The binary evolutionary model reveals that the primary has lost about half of its initial mass and is already core helium burning. Our comprehensive analysis of AzV 476 yields a consistent set of parameters and suggests previous case B mass transfer. The derived stellar masses agree within their uncertainties. The moderate masses of AzV 476 underline the scarcity of bright massive stars in the SMC. The core helium burning nature of the primary indicates that stripped stars might be hidden among OB-type populations. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.09148v1-abstract-full').style.display = 'none'; document.getElementById('2201.09148v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 January, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">18 pages + 5 pages appendix, 17 figures, 8 tables. Accepted for publication in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 659, A9 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2107.10773">arXiv:2107.10773</a> <span> [<a href="https://arxiv.org/pdf/2107.10773">pdf</a>, <a href="https://arxiv.org/format/2107.10773">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202140898">10.1051/0004-6361/202140898 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A meeting at z~3: Young massive galaxies and an AGN within 30kpc of the luminous QSO LBQS0302-0019 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Husemann%2C+B">B. Husemann</a>, <a href="/search/astro-ph?searchtype=author&query=Worseck%2C+G">G. Worseck</a>, <a href="/search/astro-ph?searchtype=author&query=Battaia%2C+F+A">F. Arrigoni Battaia</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">A. A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Shanks%2C+T">T. Shanks</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2107.10773v1-abstract-short" style="display: inline;"> Contrary to expectations from scenarios of black hole growth driven by galaxy interactions and mergers, dual active galactic nuclei (AGN) with kiloparsec separations are rarely observed and are very difficult to identify, in particular at high redshifts (i.e. z>2). Focussing on the recently discovered dual AGN system LBQS 0302-0019 at z=3.29, we seek to identify further group members in its enviro… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2107.10773v1-abstract-full').style.display = 'inline'; document.getElementById('2107.10773v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2107.10773v1-abstract-full" style="display: none;"> Contrary to expectations from scenarios of black hole growth driven by galaxy interactions and mergers, dual active galactic nuclei (AGN) with kiloparsec separations are rarely observed and are very difficult to identify, in particular at high redshifts (i.e. z>2). Focussing on the recently discovered dual AGN system LBQS 0302-0019 at z=3.29, we seek to identify further group members in its environment and to understand their formation history through deep high-angular-resolution imaging. We present deep Hubble Space Telescope (HST) Wide-field Camera 3 near-infrared imaging of LBQS 0302-0019. In combination with ground-based VLT/HAWK-I imaging, we infer accurate sizes, colours, ages, and stellar masses of companion galaxies. We clearly detect four companion objects close to LBQS 0302-0019 that also have faint signatures in the ground-based images. We constrain light-weighted ages and masses for the two most prominent companions, Jil1 and Jil2, to $t_\star=252_{-109}^{+222}$Myr with $\log(M_\star/[\mathrm{M}_\odot])= 11.2_{-0.1}^{+0.3}$ and $t_{\star}=19_{-14}^{+74}$Myr with $\log(M_\star/[\mathrm{M}_\odot])= 9.4_{-0.4}^{+0.9}$, respectively. The HST data also show that the obscured AGN, previously identified by strong nebular HeII emission, is associated with the young massive companion Jil2. Because very massive stars of the starburst cannot be solely responsible for the HeII emission, we strengthen our initial conclusion that Jil2 has been hosting an AGN. If the young starburst of Jil2 had been accompanied by sustained black hole growth, Jil2 may have contributed HeII-ionising flux to create the large HeII Ly$伪$ proximity zone around LBQS 0302-0019. Hence, the duration of the current luminous AGN episode of LBQS 0302-0019 may have been overestimated. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2107.10773v1-abstract-full').style.display = 'none'; document.getElementById('2107.10773v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 July, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">7 pages, 3 figures and 1 table. Accepted for publication in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 653, A122 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2107.02183">arXiv:2107.02183</a> <span> [<a href="https://arxiv.org/pdf/2107.02183">pdf</a>, <a href="https://arxiv.org/format/2107.02183">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnras/stab1948">10.1093/mnras/stab1948 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Superadiabaticity and the metallicity independence of the Humphreys-Davidson limit </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Sabhahit%2C+G+N">Gautham N. Sabhahit</a>, <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J+S">Jorick S. Vink</a>, <a href="/search/astro-ph?searchtype=author&query=Higgins%2C+E+R">Erin R. Higgins</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2107.02183v2-abstract-short" style="display: inline;"> The Humphreys-Davidson (HD) limit sets the boundary between evolutionary channels of massive stars that either end their lives as red supergiants (RSGs) or as the hotter blue supergiants (BSGs) and Wolf-Rayet stars. Mixing in the envelopes of massive stars close to their Eddington limit is crucial for investigating the upper luminosity limit of the coolest supergiants. We study the effects of exce… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2107.02183v2-abstract-full').style.display = 'inline'; document.getElementById('2107.02183v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2107.02183v2-abstract-full" style="display: none;"> The Humphreys-Davidson (HD) limit sets the boundary between evolutionary channels of massive stars that either end their lives as red supergiants (RSGs) or as the hotter blue supergiants (BSGs) and Wolf-Rayet stars. Mixing in the envelopes of massive stars close to their Eddington limit is crucial for investigating the upper luminosity limit of the coolest supergiants. We study the effects of excess mixing in superadiabatic layers that are dominated by radiation pressure, and we critically investigate the effects of mixing and mass loss on the evolution of RSGs with log (Teff/K) < 3.68 - as a function of metallicity. Using MESA, we produce grids of massive star models at three metallicities: Galactic (Zsol), LMC (1/2 Zsol) and SMC (1/5 Zsol), with both high and low amounts of overshooting to study the upper luminosity limit of RSGs. We systematically study the effects of excess mixing in the superadiabatic layers of post-main sequence massive stars, overshooting above the hydrogen core and yellow supergiant (YSG) mass-loss rates on the fraction of core helium burning time spent as a RSG. We find that the excess mixing in the superadiabatic layers is stronger at lower metallicities, as it depends on the opacities in the hydrogen bump at log (Teff/K) ~ 4, which become more pronounced at lower metallicity. This shifts the cutoff luminosities to lower values at lower metallicities, thus balancing the first-order effect of mass loss. The opposing effects of mass loss and excess envelope mixing during post-main sequence evolution of stars with higher overshooting potentially results in a metallicity-independent upper luminosity limit. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2107.02183v2-abstract-full').style.display = 'none'; document.getElementById('2107.02183v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 9 August, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 5 July, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in MNRAS. 15 pages, 13 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2105.12139">arXiv:2105.12139</a> <span> [<a href="https://arxiv.org/pdf/2105.12139">pdf</a>, <a href="https://arxiv.org/format/2105.12139">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnras/stab1548">10.1093/mnras/stab1548 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Evolution of Wolf-Rayet stars as black hole progenitors </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Higgins%2C+E+R">Erin R. Higgins</a>, <a href="/search/astro-ph?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J+S">Jorick S. Vink</a>, <a href="/search/astro-ph?searchtype=author&query=Hirschi%2C+R">Raphael Hirschi</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2105.12139v1-abstract-short" style="display: inline;"> Evolved Wolf-Rayet stars form a key aspect of massive star evolution, and their strong outflows determine their final fates. In this study, we calculate grids of stellar models for a wide range of initial masses at five metallicities (ranging from solar down to just 2% solar). We compare a recent hydrodynamically-consistent wind prescription with two earlier frequently-used wind recipes in stellar… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2105.12139v1-abstract-full').style.display = 'inline'; document.getElementById('2105.12139v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2105.12139v1-abstract-full" style="display: none;"> Evolved Wolf-Rayet stars form a key aspect of massive star evolution, and their strong outflows determine their final fates. In this study, we calculate grids of stellar models for a wide range of initial masses at five metallicities (ranging from solar down to just 2% solar). We compare a recent hydrodynamically-consistent wind prescription with two earlier frequently-used wind recipes in stellar evolution and population synthesis modelling, and we present the ranges of maximum final masses at core He-exhaustion for each wind prescription and metallicity Z. Our model grids reveal qualitative differences in mass-loss behaviour of the wind prescriptions in terms of "convergence". Using the prescription from Nugis & Lamers the maximum stellar black hole is found to converge to a value of 20-30Msun, independent of host metallicity, however when utilising the new physically-motivated prescription from Sander & Vink there is no convergence to a maximum black hole mass value. The final mass is simply larger for larger initial He-star mass, which implies that the upper black hole limit for He-stars below the pair-instability gap is set by prior evolution with mass loss, or the pair instability itself. Quantitatively, we find the critical Z for pair-instability (Z_PI) to be as high as 50% Zsolar, corresponding to the host metallicity of the LMC. Moreover, while the Nugis & Lamers prescription would not predict any black holes above the approx 130Msun pair-instability limit, with Sander & Vink winds included, we demonstrate a potential channel for very massive helium stars to form such massive black holes at ~2% Zsolar or below. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2105.12139v1-abstract-full').style.display = 'none'; document.getElementById('2105.12139v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 May, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in MNRAS. 17 pages, 16 figures</span> </p> </li> </ol> <nav class="pagination is-small 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