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</div> <div class="control"> <button class="button is-small is-link">Go</button> </div> </div> </form> </div> </div> <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/2502.12239">arXiv:2502.12239</a> <span> [<a href="https://arxiv.org/pdf/2502.12239">pdf</a>, <a href="https://arxiv.org/format/2502.12239">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"> Binarity at LOw Metallicity (BLOeM): Multiplicity of early B-type supergiants in the Small Magellanic Cloud </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Britavskiy%2C+N">N. Britavskiy</a>, <a href="/search/astro-ph?searchtype=author&query=Mahy%2C+L">L. Mahy</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=Patrick%2C+L+R">L. R. Patrick</a>, <a href="/search/astro-ph?searchtype=author&query=Sana%2C+H">H. Sana</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=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=Bernini-Peron%2C+M">M. Bernini-Peron</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=Bowman%2C+D+M">D. M. Bowman</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=de+Mink%2C+S+E">S. E. de Mink</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=G%C3%B6tberg%2C+Y">Y. G枚tberg</a>, <a href="/search/astro-ph?searchtype=author&query=Holgado%2C+G">G. Holgado</a>, <a href="/search/astro-ph?searchtype=author&query=Johnston%2C+C">C. Johnston</a>, <a href="/search/astro-ph?searchtype=author&query=Keszthelyi%2C+Z">Z. Keszthelyi</a>, <a href="/search/astro-ph?searchtype=author&query=Klencki%2C+J">J. Klencki</a>, <a href="/search/astro-ph?searchtype=author&query=Langer%2C+N">N. Langer</a>, <a href="/search/astro-ph?searchtype=author&query=Mandel%2C+I">I. Mandel</a>, <a href="/search/astro-ph?searchtype=author&query=Menon%2C+A">A. Menon</a>, <a href="/search/astro-ph?searchtype=author&query=Moe%2C+M">M. Moe</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> , et al. (10 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="2502.12239v1-abstract-short" style="display: inline;"> The blue supergiant (BSG) domain contains a large variety of stars whose past and future evolutionary paths are still highly uncertain. Since binary interaction plays a crucial role in the fate of massive stars, investigating the multiplicity among BSGs helps shed light on the fate of such objects. We aim to estimate the binary fraction of a large sample of BSGs in the Small Magellanic Cloud withi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.12239v1-abstract-full').style.display = 'inline'; document.getElementById('2502.12239v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2502.12239v1-abstract-full" style="display: none;"> The blue supergiant (BSG) domain contains a large variety of stars whose past and future evolutionary paths are still highly uncertain. Since binary interaction plays a crucial role in the fate of massive stars, investigating the multiplicity among BSGs helps shed light on the fate of such objects. We aim to estimate the binary fraction of a large sample of BSGs in the Small Magellanic Cloud within the Binarity at LOw Metallicity (BLOeM) survey. In total, we selected 262 targets with spectral types B0-B3 and luminosity classes I-II. This work is based on spectroscopic data collected by the GIRAFFE instrument, mounted on the Very Large Telescope, which gathered nine epochs over three months. Our spectroscopic analysis for each target includes the individual and peak-to-peak radial velocity measurements, an investigation of the line profile variability, and a periodogram analysis to search for possible short- and long-period binaries. By applying a 20 km s$^{-1}$ threshold on the peak-to-peak radial velocities above which we would consider the star to be binary, the resulting observed spectroscopic binary fraction for our BSG sample is 23 $\pm$ 3$\%$. In addition, we derived reliable orbital periods for 41 spectroscopic binaries and potential binary candidates, among which there are 17 eclipsing binaries, including 20 SB1 and SB2 systems with periods of less than 10 days. We reported a significant drop in the binary fraction of BSGs with spectral types later than B2 and effective temperatures less than 18 kK, which could indicate the end of the main sequence phase in this temperature regime. We found no metallicity dependence in the binary fraction of BSGs, compared to existing spectroscopic surveys of the Galaxy and Large Magellanic Cloud. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.12239v1-abstract-full').style.display = 'none'; document.getElementById('2502.12239v1-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> 17 February, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2025. </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, 14 figures, 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/2502.02641">arXiv:2502.02641</a> <span> [<a href="https://arxiv.org/pdf/2502.02641">pdf</a>, <a href="https://arxiv.org/format/2502.02641">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"> Binarity at Low Metallicity (BLOeM) -- Multiplicity properties of Oe and Be stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Bodensteiner%2C+J">J. Bodensteiner</a>, <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=Britavskiy%2C+N">N. Britavskiy</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=Langer%2C+N">N. Langer</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=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=Villase%C3%B1or%2C+J+I">J. I. Villase帽or</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=Bowman%2C+D+M">D. M. Bowman</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=Fabry%2C+M">M. Fabry</a>, <a href="/search/astro-ph?searchtype=author&query=Gilkis%2C+A">A. Gilkis</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=Holgado%2C+G">G. Holgado</a>, <a href="/search/astro-ph?searchtype=author&query=Izzard%2C+R+G">R. G. Izzard</a>, <a href="/search/astro-ph?searchtype=author&query=Janssens%2C+S">S. Janssens</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=Keszthelyi%2C+Z">Z. Keszthelyi</a>, <a href="/search/astro-ph?searchtype=author&query=Kub%C3%A1t%2C+J">J. Kub谩t</a>, <a href="/search/astro-ph?searchtype=author&query=Mandel%2C+I">I. Mandel</a> , et al. (18 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="2502.02641v1-abstract-short" style="display: inline;"> Rapidly rotating classical OBe stars have been proposed as the products of binary interactions, and the fraction of Be stars with compact companions implies that at least some are. However, to constrain the interaction physics spinning up the OBe stars, a large sample of homogeneously analysed OBe stars with well-determined binary characteristics and orbital parameters are required. We investigate… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.02641v1-abstract-full').style.display = 'inline'; document.getElementById('2502.02641v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2502.02641v1-abstract-full" style="display: none;"> Rapidly rotating classical OBe stars have been proposed as the products of binary interactions, and the fraction of Be stars with compact companions implies that at least some are. However, to constrain the interaction physics spinning up the OBe stars, a large sample of homogeneously analysed OBe stars with well-determined binary characteristics and orbital parameters are required. We investigate the multiplicity properties of a sample of 18 Oe, 62 Be, and two Of?p stars observed within the BLOeM survey in the Small Magellanic Cloud. We analyse the first nine epochs of spectroscopic observations obtained over approximately three months in 2023. Radial velocities (RVs) of all stars are measured. Applying commonly-used binarity criteria we classify objects as binaries, binary candidates, and apparently single (RV stable) objects. We further inspect the spectra for double-lined spectroscopic binaries and cross-match with catalogues of X-ray sources and photometric binaries. We classify 14 OBe stars as binaries, and an additional 11 as binary candidates. The two Of?p stars are apparently single. Two more objects are most likely currently interacting binaries. Without those, the observed binary fraction for the OBe sample (78 stars) is f_OBe_obs=0.18+/-0.04 (f_obs_cand=0.32+/-0.05 including candidates). This fraction is less than half of that measured for OB stars in BLOeM. Combined with the lower fraction of SB2s, this suggests that OBe stars have indeed fundamentally different binary properties than OB stars. We find no evidence for OBe binaries with massive compact companions, in contrast to expectations from binary population synthesis. Our results support the binary scenario as an important formation channel for OBe stars, as post-interaction binaries may have been disrupted or the stripped companions of OBe stars are harder to detect. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.02641v1-abstract-full').style.display = 'none'; document.getElementById('2502.02641v1-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 February, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2025. </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">12 pages (+appendix), 7 figures, 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/2412.07373">arXiv:2412.07373</a> <span> [<a href="https://arxiv.org/pdf/2412.07373">pdf</a>, <a href="https://arxiv.org/format/2412.07373">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/10.1051/0004-6361/202450033">10.1051/0004-6361/202450033 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Determining stellar properties of massive stars in NGC346 in the SMC with a Bayesian statistic technique </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=Pauli%2C+D">D. Pauli</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=Todt%2C+H">H. Todt</a>, <a href="/search/astro-ph?searchtype=author&query=Sch%C3%B6sser%2C+E+C">E. C. Sch枚sser</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=Zeidler%2C+P">P. Zeidler</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="2412.07373v1-abstract-short" style="display: inline;"> NGC 346 is a young cluster with numerous hot OB stars. It is part of the Small Magellanic Cloud (SMC), and has an average metallicity that is one-seventh of the Milky Way's. A detailed study of its stellar content provides a unique opportunity to understand the stellar and wind properties of massive stars in low-metallicity environments, and enables us to improve our understanding of star formatio… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2412.07373v1-abstract-full').style.display = 'inline'; document.getElementById('2412.07373v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2412.07373v1-abstract-full" style="display: none;"> NGC 346 is a young cluster with numerous hot OB stars. It is part of the Small Magellanic Cloud (SMC), and has an average metallicity that is one-seventh of the Milky Way's. A detailed study of its stellar content provides a unique opportunity to understand the stellar and wind properties of massive stars in low-metallicity environments, and enables us to improve our understanding of star formation and stellar evolution. The fundamental stellar parameters defining a star's spectral appearance are its effective surface temperature, surface gravity, and projected rotational velocity. Unfortunately, these parameters cannot be obtained independently from only H and He spectral features as they are partially degenerate. With this work we aim to overcome this degeneracy by applying a newly developed Bayesian statistic technique that can fit these three parameters simultaneously. Multi-epoch optical spectra are used in combination with a Bayesian statistic technique to fit stellar properties based on a publicly available grid of synthetic spectra of stellar atmospheres. The use of all of the multi-epoch observations simultaneously allows the identification of binaries. The stellar parameters for 34 OB stars within the core of NGC 346 are derived and presented here. By the use of both $\mathrm{He}\textsc{i}$ and $\mathrm{He}\textsc{ii}$ lines, the partial degeneracy between the stellar parameters of effective surface temperature, surface gravity, and projected rotational velocity is overcome. A lower limit to the binary fraction of the sample of stars is found to be at least 46%. Based on comparisons with analysis conducted on an overlapping sample of stars within NGC 346, the Bayesian statistic technique approach is shown to be a viable method to measure stellar parameters for hot massive stars in low-metallicity environments even when only low-resolution spectra are available.} <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2412.07373v1-abstract-full').style.display = 'none'; document.getElementById('2412.07373v1-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 December, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 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. 11 figures. Additional figures available, see https://doi.org/10.5281/zenodo.13991997</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> M. Rickard et al. (2024) A149 </p> </li> <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/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/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/2407.03137">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 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/10.1051/0004-6361/202449665">10.1051/0004-6361/202449665 <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 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> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 692, A90 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2406.13589">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/2405.01267">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/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/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/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/2303.03989">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/2302.10299">arXiv:2302.10299</a> <span> [<a href="https://arxiv.org/pdf/2302.10299">pdf</a>, <a href="https://arxiv.org/format/2302.10299">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"> Massive star feedback in the Magellanic Clouds and the tidal Bridge </p> <p class="authors"> <span class="search-hit">Authors:</span> <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="2302.10299v1-abstract-short" style="display: inline;"> Massive stars have far-reaching feedback effects that alter the surrounding environment on local, global, and cosmic scales. Spectral analyses of massive stars with adequate stellar-atmosphere models are important to study massive star feedback in detail. We discuss the most recent UV and optical studies of massive metal-poor stars, including those with metallicities ranging from half to one twent… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.10299v1-abstract-full').style.display = 'inline'; document.getElementById('2302.10299v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2302.10299v1-abstract-full" style="display: none;"> Massive stars have far-reaching feedback effects that alter the surrounding environment on local, global, and cosmic scales. Spectral analyses of massive stars with adequate stellar-atmosphere models are important to study massive star feedback in detail. We discuss the most recent UV and optical studies of massive metal-poor stars, including those with metallicities ranging from half to one twentieth of solar, connected with large-scale ISM structures in the Magellanic Clouds and the tidal Magellanic Bridge. We present ionizing fluxes from massive stars with low metallicity along with mechanical energy, and we further compare these to the observed energetics in the ISM. The results give hints on the leakage of hot gas and ionizing photons in the Magellanic Clouds. The paper outlines feedback from individual massive stars to population-level collective feedback, the significance of various feedback mechanisms (radiation, wind, supernova), and the influence by the physical conditions of the ISM <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.10299v1-abstract-full').style.display = 'none'; document.getElementById('2302.10299v1-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> 17 November, 2022; <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">International Astronomical Union Proceedings Series</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/2211.12153">arXiv:2211.12153</a> <span> [<a href="https://arxiv.org/pdf/2211.12153">pdf</a>, <a href="https://arxiv.org/format/2211.12153">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"> Winds of OB stars: impact of metallicity, rotation and binary interaction </p> <p class="authors"> <span class="search-hit">Authors:</span> <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="2211.12153v1-abstract-short" style="display: inline;"> Winds of massive stars are an important ingredient in determining their evolution, final remnant mass, and feedback to the surrounding interstellar medium. We compare empirical results for OB star winds at low metallicity with theoretical predictions. Observations suggest very weak winds at SMC metallicity, but there are exceptions. We identified promising candidates for rotationally enhanced mass… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.12153v1-abstract-full').style.display = 'inline'; document.getElementById('2211.12153v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2211.12153v1-abstract-full" style="display: none;"> Winds of massive stars are an important ingredient in determining their evolution, final remnant mass, and feedback to the surrounding interstellar medium. We compare empirical results for OB star winds at low metallicity with theoretical predictions. Observations suggest very weak winds at SMC metallicity, but there are exceptions. We identified promising candidates for rotationally enhanced mass-loss rates with two component wind and partially stripped stars hiding among OB stars with slow but dense wind in the SMC. A preliminary analysis of these systems, derived parameters, and their implications are discussed. Finally, we briefly discuss the interaction of OB winds near black holes in X-ray binaries. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.12153v1-abstract-full').style.display = 'none'; document.getElementById('2211.12153v1-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 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">Accepted for publication 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/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/2205.05147">arXiv:2205.05147</a> <span> [<a href="https://arxiv.org/pdf/2205.05147">pdf</a>, <a href="https://arxiv.org/format/2205.05147">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/10.1088/1538-3873/ac697b">10.1088/1538-3873/ac697b <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Ionization and Star Formation in the Giant HII Region SMC-N66 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Geist%2C+E">E. Geist</a>, <a href="/search/astro-ph?searchtype=author&query=Gallagher%2C+J+S">J. S. Gallagher</a>, <a href="/search/astro-ph?searchtype=author&query=Kotulla%2C+R">R. Kotulla</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=Ramachandran%2C+V">V. Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Sabbi%2C+E">E. Sabbi</a>, <a href="/search/astro-ph?searchtype=author&query=Smith%2C+L">L. Smith</a>, <a href="/search/astro-ph?searchtype=author&query=Kniazev%2C+A">A. Kniazev</a>, <a href="/search/astro-ph?searchtype=author&query=Nota%2C+A">A. Nota</a>, <a href="/search/astro-ph?searchtype=author&query=Rickard%2C+M+J">M. 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="2205.05147v1-abstract-short" style="display: inline;"> The NGC 346 young stellar system and associated N66 giant HII region in the Small Magellanic Cloud are the nearest example of a massive star forming event in a low metallicity ($Z\approx0.2Z_{\odot}$) galaxy. With an age of $\lesssim$3Myr this system provides a unique opportunity to study relationships between massive stars and their associated HII region. Using archival data, we derive a total H… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.05147v1-abstract-full').style.display = 'inline'; document.getElementById('2205.05147v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2205.05147v1-abstract-full" style="display: none;"> The NGC 346 young stellar system and associated N66 giant HII region in the Small Magellanic Cloud are the nearest example of a massive star forming event in a low metallicity ($Z\approx0.2Z_{\odot}$) galaxy. With an age of $\lesssim$3Myr this system provides a unique opportunity to study relationships between massive stars and their associated HII region. Using archival data, we derive a total H$伪$ luminosity of L(H$伪$)=4.1$\times$10$^{38}$ergs$^{-1}$ corresponding to an H-photoionization rate of 3$\times$10$^{50}$s$^{-1}$. A comparison with a predicted stellar ionization rate derived from the more than 50 known O-stars in NGC 346, including massive stars recently classified from HST FUV spectra, indicates an approximate ionization balance. Spectra obtained with SALT suggest the ionization structure of N66 could be consistent with some leakage of ionizing photons. Due to the low metallicity, the far ultraviolet luminosity from NGC 346 is not confined to the interstellar cloud associated with N66. Ionization extends through much of the spatial extent of the N66 cloud complex, and most of the cloud mass is not ionized. The stellar mass estimated from nebular L(H$伪$) appears to be lower than masses derived from the census of resolved stars which may indicate a disconnect between the formation of high and low mass stars in this region. We briefly discuss implications of the properties of N66 for studies of star formation and stellar feedback in low metallicity environments. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.05147v1-abstract-full').style.display = 'none'; document.getElementById('2205.05147v1-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 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">15 pages, 6 figures, Accepted to be published in PASP</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/2102.03102">arXiv:2102.03102</a> <span> [<a href="https://arxiv.org/pdf/2102.03102">pdf</a>, <a href="https://arxiv.org/format/2102.03102">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/10.1093/mnras/stab383">10.1093/mnras/stab383 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The excess of cool supergiants from contemporary stellar evolution models defies the metallicity-independent Humphreys-Davidson limit </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Gilkis%2C+A">Avishai Gilkis</a>, <a href="/search/astro-ph?searchtype=author&query=Shenar%2C+T">Tomer Shenar</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">Varsha Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Jermyn%2C+A+S">Adam S. Jermyn</a>, <a href="/search/astro-ph?searchtype=author&query=Mahy%2C+L">Laurent Mahy</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=Arcavi%2C+I">Iair Arcavi</a>, <a href="/search/astro-ph?searchtype=author&query=Sana%2C+H">Hugues Sana</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="2102.03102v1-abstract-short" style="display: inline;"> The Humphreys-Davidson (HD) limit empirically defines a region of high luminosities (log L > 5.5) and low effective temperatures (T < 20kK) on the Hertzsprung-Russell Diagram in which hardly any supergiant stars are observed. Attempts to explain this limit through instabilities arising in near- or super-Eddington winds have been largely unsuccessful. Using modern stellar evolution we aim to re-exa… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2102.03102v1-abstract-full').style.display = 'inline'; document.getElementById('2102.03102v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2102.03102v1-abstract-full" style="display: none;"> The Humphreys-Davidson (HD) limit empirically defines a region of high luminosities (log L > 5.5) and low effective temperatures (T < 20kK) on the Hertzsprung-Russell Diagram in which hardly any supergiant stars are observed. Attempts to explain this limit through instabilities arising in near- or super-Eddington winds have been largely unsuccessful. Using modern stellar evolution we aim to re-examine the HD limit, investigating the impact of enhanced mixing on massive stars. We construct grids of stellar evolution models appropriate for the Small and Large Magellanic Clouds (SMC, LMC), as well as for the Galaxy, spanning various initial rotation rates and convective overshooting parameters. Significantly enhanced mixing apparently steers stellar evolution tracks away from the region of the HD limit. To quantify the excess of over-luminous stars in stellar evolution simulations we generate synthetic populations of massive stars, and make detailed comparisons with catalogues of cool (T < 12.5kK) and luminous (log L > 4.7) stars in the SMC and LMC. We find that adjustments to the mixing parameters can lead to agreement between the observed and simulated red supergiant populations, but for hotter supergiants the simulations always over-predict the number of very luminous (log L > 5.4) stars compared to observations. The excess of luminous supergiants decreases for enhanced mixing, possibly hinting at an important role mixing has in explaining the HD limit. Still, the HD limit remains unexplained for hotter supergiants. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2102.03102v1-abstract-full').style.display = 'none'; document.getElementById('2102.03102v1-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> 5 February, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 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</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2011.08006">arXiv:2011.08006</a> <span> [<a href="https://arxiv.org/pdf/2011.08006">pdf</a>, <a href="https://arxiv.org/format/2011.08006">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/10.1051/0004-6361/202039486">10.1051/0004-6361/202039486 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Discovery of O stars in the tidal Magellanic Bridge: Stellar parameters, abundances, and feedback of the nearest metal-poor massive stars and their implication for the Magellanic System ecology </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">Varsha 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> </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="2011.08006v1-abstract-short" style="display: inline;"> The Magellanic Bridge stretching between the SMC and LMC is the nearest tidally stripped intergalactic environment and has a low average metallicity of $Z~0.1Z_{\odot}$. Here we report the first discovery of three O-type stars in the Bridge using archival spectra collected with FLAMES at ESO/VLT. We analyze the spectra using the PoWR models, which provide the physical parameters, ionizing photon f… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2011.08006v1-abstract-full').style.display = 'inline'; document.getElementById('2011.08006v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2011.08006v1-abstract-full" style="display: none;"> The Magellanic Bridge stretching between the SMC and LMC is the nearest tidally stripped intergalactic environment and has a low average metallicity of $Z~0.1Z_{\odot}$. Here we report the first discovery of three O-type stars in the Bridge using archival spectra collected with FLAMES at ESO/VLT. We analyze the spectra using the PoWR models, which provide the physical parameters, ionizing photon fluxes, and surface abundances. This discovery suggests that the tidally stripped low density gas is capable of producing massive O stars and their ages imply ongoing star formation in the Bridge. The multi-epoch spectra indicate that all three O stars are binaries. Despite their spatial proximity to each other, these O stars are chemically distinct. One of them is a fast-rotating giant with nearly LMC-like abundances. The other two are main-sequence stars that rotate extremely slowly and are strongly metal depleted. This includes the most nitrogen-poor O star known up to date. Taking into account the previous analyses of B stars in the Bridge, we interpret the various metal abundances as the signature of a chemically inhomogeneous interstellar medium, suggesting that the gas might have accreted during multiple episodes of tidal interaction between the Clouds. Attributing the lowest derived metal content to the primordial gas, the time of initial formation of the Bridge may date back to several Gyr. Using the Gaia and Galex color-magnitude diagrams we roughly estimate the total number of O stars in the Bridge and their total ionizing radiation. Comparing with the energetics of the diffuse ISM, we find that the contribution of the hot stars to the ionizing radiation field in the Bridge is less than 10%, and conclude that the main sources of ionizing photons are leaks from the LMC and SMC. We estimate a lower limit for the fraction of ionizing radiation that escapes from these two dwarf galaxies. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2011.08006v1-abstract-full').style.display = 'none'; document.getElementById('2011.08006v1-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 November, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2020. </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">to be published 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 646, A16 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2005.12595">arXiv:2005.12595</a> <span> [<a href="https://arxiv.org/pdf/2005.12595">pdf</a>, <a href="https://arxiv.org/ps/2005.12595">ps</a>, <a href="https://arxiv.org/format/2005.12595">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/aba49e">10.3847/1538-4357/aba49e <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Phase-dependent study of near-infrared disk emission lines in LB-1 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Liu%2C+J">Jifeng Liu</a>, <a href="/search/astro-ph?searchtype=author&query=Zheng%2C+Z">Zheng Zheng</a>, <a href="/search/astro-ph?searchtype=author&query=Soria%2C+R">Roberto Soria</a>, <a href="/search/astro-ph?searchtype=author&query=Aceituno%2C+J">Jesus Aceituno</a>, <a href="/search/astro-ph?searchtype=author&query=Zhang%2C+H">Haotong Zhang</a>, <a href="/search/astro-ph?searchtype=author&query=Lu%2C+Y">Youjun Lu</a>, <a href="/search/astro-ph?searchtype=author&query=Wang%2C+S">Song Wang</a>, <a href="/search/astro-ph?searchtype=author&query=Hamann%2C+W">Wolf-Rainer Hamann</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L+M">Lida M. Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">Varsha Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Yuan%2C+H">Hailong Yuan</a>, <a href="/search/astro-ph?searchtype=author&query=Bai%2C+Z">Zhongrui Bai</a>, <a href="/search/astro-ph?searchtype=author&query=Wang%2C+S">Shu Wang</a>, <a href="/search/astro-ph?searchtype=author&query=McKee%2C+B+J">Brendan J. McKee</a>, <a href="/search/astro-ph?searchtype=author&query=Wu%2C+J">Jianfeng Wu</a>, <a href="/search/astro-ph?searchtype=author&query=Wang%2C+J">Junfeng Wang</a>, <a href="/search/astro-ph?searchtype=author&query=Lattanzi%2C+M">Mario Lattanzi</a>, <a href="/search/astro-ph?searchtype=author&query=Belczynski%2C+K">Krzysztof Belczynski</a>, <a href="/search/astro-ph?searchtype=author&query=Casares%2C+J">Jorge Casares</a>, <a href="/search/astro-ph?searchtype=author&query=Simon-Diaz%2C+S">Sergio Simon-Diaz</a>, <a href="/search/astro-ph?searchtype=author&query=Hern%C3%A1ndez%2C+J+I+G">Jonay I. Gonz谩lez Hern谩ndez</a>, <a href="/search/astro-ph?searchtype=author&query=Rebolo%2C+R">Rafael Rebolo</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="2005.12595v1-abstract-short" style="display: inline;"> The mass, origin and evolutionary stage of the binary system LB-1 has been the subject of intense debate, following the claim that it hosts an $\sim$70$M_{\odot}$ black hole, in stark contrast with the expectations for stellar remnants in the Milky Way. We conducted a high-resolution, phase-resolved spectroscopic study of the near-infrared Paschen lines in this system, using the 3.5-m telescope at… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2005.12595v1-abstract-full').style.display = 'inline'; document.getElementById('2005.12595v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2005.12595v1-abstract-full" style="display: none;"> The mass, origin and evolutionary stage of the binary system LB-1 has been the subject of intense debate, following the claim that it hosts an $\sim$70$M_{\odot}$ black hole, in stark contrast with the expectations for stellar remnants in the Milky Way. We conducted a high-resolution, phase-resolved spectroscopic study of the near-infrared Paschen lines in this system, using the 3.5-m telescope at Calar Alto Observatory. We find that Pa$尾$ and Pa$纬$ (after proper subtraction of the stellar absorption component) are well fitted with a standard double-peaked model, typical of disk emission. We measured the velocity shifts of the red and blue peaks at 28 orbital phases: the line center has an orbital motion in perfect antiphase with the stellar motion, and the radial velocity amplitude ranges from 8 to 13 km/s for different choices of lines and profile modelling. We interpret this curve as proof that the disk is tracing the orbital motion of the primary, ruling out the circumbinary disk and the hierarchical triple scenarios. The phase-averaged peak-to-peak half-separation (proxy for the projected rotational velocity of the outer disk) is $\sim$70 km s$^{-1}$, larger than the stellar orbital velocity and also inconsistent with a circumbinary disk. From those results, we infer a primary mass 4--8 times higher than the secondary mass. Moreover, we show that the ratio of the blue and red peaks (V/R intensity ratio) has a sinusoidal behaviour in phase with the secondary star, which can be interpreted as the effect of external irradiation by the secondary star on the outer disk. Finally, we briefly discuss our findings in the context of alternative scenarios recently proposed for LB-1. Definitive tests between alternative solutions will require further astrometric data from $Gaia$. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2005.12595v1-abstract-full').style.display = 'none'; document.getElementById('2005.12595v1-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 May, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2020. </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">To be submitted to ApJ. Comments are welcome</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1912.08953">arXiv:1912.08953</a> <span> [<a href="https://arxiv.org/pdf/1912.08953">pdf</a>, <a href="https://arxiv.org/format/1912.08953">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/10.1051/0004-6361/201834314">10.1051/0004-6361/201834314 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Testing massive star evolution, star-formation history, and feedback at low metallicity: Photometric analysis of OB stars in the SMC Wing </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Fulmer%2C+L+M">Leah M. Fulmer</a>, <a href="/search/astro-ph?searchtype=author&query=Gallagher%2C+J+S">John S. Gallagher III</a>, <a href="/search/astro-ph?searchtype=author&query=Hamann%2C+W">Wolf-Rainer Hamann</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L+M">Lida M. Oskinova</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="1912.08953v2-abstract-short" style="display: inline;"> The supergiant ionized shell SMC-SGS 1 (DEM 167), located in the outer Wing of the Small Magellanic Cloud (SMC), resembles structures that originate from an energetic star-formation event and later stimulate star formation as they expand into the ambient medium. However, stellar populations within and surrounding SMC-SGS 1 tell a different story. We present a photometric study of the stellar popul… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.08953v2-abstract-full').style.display = 'inline'; document.getElementById('1912.08953v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1912.08953v2-abstract-full" style="display: none;"> The supergiant ionized shell SMC-SGS 1 (DEM 167), located in the outer Wing of the Small Magellanic Cloud (SMC), resembles structures that originate from an energetic star-formation event and later stimulate star formation as they expand into the ambient medium. However, stellar populations within and surrounding SMC-SGS 1 tell a different story. We present a photometric study of the stellar population encompassed by SMC-SGS 1 in order to trace the history of this structure and its potential influence on star formation within the low-density, low-metallicity SMC Wing. For a stellar population that is physically associated with SMC-SGS 1, we combined near-ultraviolet (NUV) photometry from the Galaxy Evolution Explorer (GALEX) with archival optical (V-band) photometry from the ESO Danish 1.54m Telescope. Given their colors and luminosities, we estimated stellar ages and masses by matching observed photometry to theoretical stellar isochrone models. We find that the investigated region supports an active, extended star-formation event spanning $\sim$ 25 - 40 Myr ago, as well as continued star formation into the present. Using a standard initial mass function (IMF), we infer a lower bound on the stellar mass from this period of $\sim 3 \times 10^4 M_{\odot}$, corresponding to a star-formation intensity of $\sim$ 6 $\times$ 10$^{-3}$ M$_{\odot}$ kpc$^{-2}$ yr$^{-1}$. The spatial and temporal distributions of young stars encompassed by SMC-SGS 1 imply a slow, consistent progression of star formation over millions of years. Ongoing star formation along the edge of and interior to SMC-SGS 1 suggests a combined stimulated and stochastic mode of star formation within the SMC Wing. A slow expansion of the shell within this low-density environment may preserve molecular clouds within the volume of the shell, leaving them to form stars even after nearby stellar feedback expels local gas and dust. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.08953v2-abstract-full').style.display = 'none'; document.getElementById('1912.08953v2-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 December, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 18 December, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2019. </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">9 pages, 6 figures, 3 tables</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 633, A164 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1905.09296">arXiv:1905.09296</a> <span> [<a href="https://arxiv.org/pdf/1905.09296">pdf</a>, <a href="https://arxiv.org/format/1905.09296">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/10.1051/0004-6361/201935684e">10.1051/0004-6361/201935684e <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Wolf-Rayet binaries of the nitrogen sequence in the Large Magellanic Cloud: spectroscopy, orbital analysis, formation, and evolution </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=Sablowski%2C+D+P">D. P. Sablowski</a>, <a href="/search/astro-ph?searchtype=author&query=Hainich%2C+R">R. Hainich</a>, <a href="/search/astro-ph?searchtype=author&query=Todt%2C+H">H Todt</a>, <a href="/search/astro-ph?searchtype=author&query=Moffat%2C+A+F+J">A. F. J. Moffat</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=Ramachandran%2C+V">V. Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Sana%2C+H">H. Sana</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=Schnurr%2C+O">O. Schnurr</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=Vanbeveren%2C+D">D. Vanbeveren</a>, <a href="/search/astro-ph?searchtype=author&query=Goetberg%2C+Y">Y. Goetberg</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="1905.09296v3-abstract-short" style="display: inline;"> Massive Wolf-Rayet (WR) stars dominate the radiative and mechanical energy budget of galaxies and probe a critical phase in the evolution of massive stars prior to core-collapse. It is not known whether core He-burning WR stars (classical WR, cWR) form predominantly through wind-stripping (w-WR) or binary stripping (b-WR). With spectroscopy of WR binaries so-far largely avoided due to its complexi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.09296v3-abstract-full').style.display = 'inline'; document.getElementById('1905.09296v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1905.09296v3-abstract-full" style="display: none;"> Massive Wolf-Rayet (WR) stars dominate the radiative and mechanical energy budget of galaxies and probe a critical phase in the evolution of massive stars prior to core-collapse. It is not known whether core He-burning WR stars (classical WR, cWR) form predominantly through wind-stripping (w-WR) or binary stripping (b-WR). With spectroscopy of WR binaries so-far largely avoided due to its complexity, our study focuses on the 44 WR binaries / binary candidates of the Large Magellanic Cloud (LMC, metallicity Z~0.5 Zsun), identified on the basis of radial velocity variations, composite spectra, or high X-ray luminosities. Relying on a diverse spectroscopic database, we aim to derive the physical and orbital parameters of our targets, confronting evolution models of evolved massive stars at sub-solar metallicity, and constraining the impact of binary interaction in forming them. Spectroscopy is performed using the Potsdam Wolf-Rayet (PoWR) code and cross-correlation techniques. Disentanglement is performed using the code Spectangular or the shift-and-add algorithm. Evolutionary status is interpreted using the Binary Population and Spectral Synthesis (BPASS) code, exploring binary interaction and chemically-homogeneous evolution. No obvious dichotomy in the locations of apparently-single and binary WN stars on the Hertzsprung-Russell diagram is apparent. According to commonly used stellar evolution models (BPASS, Geneva), most apparently-single WN stars could not have formed as single stars, implying that they were stripped by an undetected companion. Otherwise, it must follow that pre-WR mass-loss/mixing (e.g., during the red supergiant phase) are strongly underestimated in standard stellar evolution models. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.09296v3-abstract-full').style.display = 'none'; document.getElementById('1905.09296v3-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> 8 September, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 22 May, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2019. </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 10.05.2019; 69 pages (25 main paper + 44 appendix); Corrigendum: Shenar et al. 2020, A&A, 641, 2: An unfortunate typo in the implementation of the "transformed radius" caused errors of up to ~0.5dex in the derived mass-loss rates. This has now been corrected</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 641, C2 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1904.04687">arXiv:1904.04687</a> <span> [<a href="https://arxiv.org/pdf/1904.04687">pdf</a>, <a href="https://arxiv.org/ps/1904.04687">ps</a>, <a href="https://arxiv.org/format/1904.04687">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/10.1051/0004-6361/201834850">10.1051/0004-6361/201834850 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Galactic WN stars revisited. Impact of Gaia distances on fundamental stellar parameters </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Hamann%2C+W+-">W. -R. Hamann</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=Liermann%2C+A">A. Liermann</a>, <a href="/search/astro-ph?searchtype=author&query=Hainich%2C+R">R. Hainich</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=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=Oskinova%2C+L+M">L. M. Oskinova</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="1904.04687v1-abstract-short" style="display: inline;"> Comprehensive spectral analyses of the Galactic Wolf-Rayet stars of the nitrogen sequence (i.e.\ the WN subclass) have been performed in a previous paper. However, the distances of these objects were poorly known. Distances have a direct impact on the "absolute" parameters, such as luminosities and mass-loss rates. The recent Gaia Data Release (DR2) of trigonometric parallaxes includes nearly all… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1904.04687v1-abstract-full').style.display = 'inline'; document.getElementById('1904.04687v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1904.04687v1-abstract-full" style="display: none;"> Comprehensive spectral analyses of the Galactic Wolf-Rayet stars of the nitrogen sequence (i.e.\ the WN subclass) have been performed in a previous paper. However, the distances of these objects were poorly known. Distances have a direct impact on the "absolute" parameters, such as luminosities and mass-loss rates. The recent Gaia Data Release (DR2) of trigonometric parallaxes includes nearly all WN stars of our Galactic sample. In the present paper, we apply the new distances to the previously analyzed Galactic WN stars and rescale the results accordingly. On this basis, we present a revised catalog of 55 Galactic WN stars with their stellar and wind parameters. The correlations between mass-loss rate and luminosity show a large scatter, for the hydrogen-free WN stars as well as for those with detectable hydrogen. The slopes of the $\log L - \log \dot{M}$ correlations are shallower than found previously. The empirical Hertzsprung-Russell diagram (HRD) still shows the previously established dichotomy between the hydrogen-free early WN subtypes that are located on the hot side of the zero-age main sequence (ZAMS), and the late WN subtypes, which show hydrogen and reside mostly at cooler temperatures than the ZAMS (with few exceptions). However, with the new distances, the distribution of stellar luminosities became more continuous than obtained previously. The hydrogen-showing stars of late WN subtype are still found to be typically more luminous than the hydrogen-free early subtypes, but there is a range of luminosities where both subclasses overlap. The empirical HRD of the Galactic single WN stars is compared with recent evolutionary tracks. Neither these single-star evolutionary models nor binary scenarios can provide a fully satisfactory explanation for the parameters of these objects and their location in the HRD. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1904.04687v1-abstract-full').style.display = 'none'; document.getElementById('1904.04687v1-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 April, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2019. </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; 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 625, A57 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1903.01762">arXiv:1903.01762</a> <span> [<a href="https://arxiv.org/pdf/1903.01762">pdf</a>, <a href="https://arxiv.org/format/1903.01762">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/10.1051/0004-6361/201935365">10.1051/0004-6361/201935365 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Testing massive star evolution, star-formation history and feedback at low metallicity : Spectroscopic analysis of OB stars in the SMC Wing </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">Varsha Ramachandran</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=Gallagher%2C+J+S">J. S. Gallagher</a>, <a href="/search/astro-ph?searchtype=author&query=Hainich%2C+R">R. Hainich</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=Todt%2C+H">H. Todt</a>, <a href="/search/astro-ph?searchtype=author&query=Fulmer%2C+L">L. Fulmer</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="1903.01762v3-abstract-short" style="display: inline;"> Stars which start their lives with spectral types O and early-B are the progenitors of core-collapse supernovae, long gamma-ray bursts, neutron stars, and black holes. These massive stars are the primary sources of stellar feedback in star-forming galaxies. At low metallicities, the properties of massive stars and their evolution are not yet fully explored. Here we report a spectroscopic study of… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1903.01762v3-abstract-full').style.display = 'inline'; document.getElementById('1903.01762v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1903.01762v3-abstract-full" style="display: none;"> Stars which start their lives with spectral types O and early-B are the progenitors of core-collapse supernovae, long gamma-ray bursts, neutron stars, and black holes. These massive stars are the primary sources of stellar feedback in star-forming galaxies. At low metallicities, the properties of massive stars and their evolution are not yet fully explored. Here we report a spectroscopic study of 320 OB stars in the Small Magellanic Cloud. The data, which we obtained with the ESO Very Large Telescope, were analyzed using state-of-the-art stellar atmosphere models. We find that stellar winds of our sample stars are much weaker than theoretically expected. The stellar rotation rates show a bi-modal distribution. The well-populated upper Hertzsprung-Russell diagram including our sample OB stars from SMC Wing as well as additional evolved stars all over SMC from the literature shows a strict luminosity limit. The comparison with single-star evolutionary tracks suggests a dichotomy in the fate of massive stars in the SMC. Only stars with Minit<30M$_{\odot}$ seem to evolve from the main sequence to the cool side of the HRD to become a red supergiant and to explode as type II-P supernova. In contrast, stars with Minit>30M$_{\odot}$ appear to stay always hot and might evolve quasi chemically homogeneously, finally collapsing to relatively massive black holes. However, we find no indication that chemical mixing is correlated with rapid rotation. We report extended star-formation episodes in a quiescent low-density region of the Wing, which is progressing stochastically. We measure the key parameters of stellar feedback and establish the links between the rates of star formation and supernovae. Our study reveals that in metal-poor environments the stellar feedback is dominated by core-collapse supernovae in combination with winds and ionizing radiation supplied by a few of the most massive stars. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1903.01762v3-abstract-full').style.display = 'none'; document.getElementById('1903.01762v3-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 April, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 5 March, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2019. </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 625, A104 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1811.07820">arXiv:1811.07820</a> <span> [<a href="https://arxiv.org/pdf/1811.07820">pdf</a>, <a href="https://arxiv.org/format/1811.07820">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/10.1051/0004-6361/201833178">10.1051/0004-6361/201833178 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The extreme O-type spectroscopic binary HD 93129A </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Gruner%2C+D">D. Gruner</a>, <a href="/search/astro-ph?searchtype=author&query=Hainich%2C+R">R. Hainich</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=Todt%2C+H">H. Todt</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=Ramachandran%2C+V">V. Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Ayres%2C+T">T. Ayres</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="1811.07820v2-abstract-short" style="display: inline;"> HD 93129A was classified as the earliest O-type star in the Galaxy (O2~If*) and is considered as the prototype of its spectral class. However, interferometry shows that this object is a binary system, while recent observations even suggest a triple configuration. None of the previous spectral analyses of this object accounted for its multiplicity. With new high-resolution UV and optical spectra, w… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1811.07820v2-abstract-full').style.display = 'inline'; document.getElementById('1811.07820v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1811.07820v2-abstract-full" style="display: none;"> HD 93129A was classified as the earliest O-type star in the Galaxy (O2~If*) and is considered as the prototype of its spectral class. However, interferometry shows that this object is a binary system, while recent observations even suggest a triple configuration. None of the previous spectral analyses of this object accounted for its multiplicity. With new high-resolution UV and optical spectra, we have the possibility to reanalyze this key object, taking its binary nature into account for the first time. We aim to derive the fundamental parameters and the evolutionary status of HD 93129A, identifying the contributions of both components to the composite spectrum. We analyzed UV and optical observations acquired with the Hubble Space Telescope and ESO's Very Large Telescope. A multiwavelength analysis of the system was performed using the latest version of the Potsdam Wolf-Rayet model atmosphere code. Despite the similar spectral types of the two components, we are able to find signatures from each of the components in the combined spectrum, which allows us to estimate the parameters of both stars. We derive $\log (L/L_\odot) = 6.15$, $T_{\textrm{eff}}=52$ kK, and $\log \dot{M}=-4.7 [M_\odot\text{yr}^{-1}]$ for the primary Aa, and $\log (L/L_\odot)=5.58$, $T_{\textrm{eff}}=45$ kK, and $\log\dot{M}=-5.8 [M_\odot\text{yr}^{-1}]$ for the secondary Ab. Even when accounting for the binary nature, the primary of HD 93129A is found to be one of the hottest and most luminous O stars in our Galaxy. Based on the theoretical decomposition of the spectra, we assign spectral types O2~If* and O3~III(f*) to components Aa and Ab, respectively. While we achieve a good fit for a wide spectral range, specific spectral features are not fully reproduced. The data are not sufficient to identify contributions from a hypothetical third component in the system. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1811.07820v2-abstract-full').style.display = 'none'; document.getElementById('1811.07820v2-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> 14 January, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 19 November, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2018. </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, 20 figures, accepted for publication in Astronomy & Astrophysics, typos corrected by language editor</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 621, A63 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1811.06307">arXiv:1811.06307</a> <span> [<a href="https://arxiv.org/pdf/1811.06307">pdf</a>, <a href="https://arxiv.org/format/1811.06307">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/10.1051/0004-6361/201833787">10.1051/0004-6361/201833787 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> PoWR grids of non-LTE model atmospheres for OB-type stars of various metallicities </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Hainich%2C+R">R. Hainich</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">V. Ramachandran</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=Todt%2C+H">H. Todt</a>, <a href="/search/astro-ph?searchtype=author&query=Gruner%2C+D">D. Gruner</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="1811.06307v1-abstract-short" style="display: inline;"> The study of massive stars in different metallicity environments is a central topic of current stellar research. The spectral analysis of massive stars requires adequate model atmospheres. The computation of such models is difficult and time-consuming. Therefore, spectral analyses are greatly facilitated if they can refer to existing grids of models. Here we provide grids of model atmospheres for… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1811.06307v1-abstract-full').style.display = 'inline'; document.getElementById('1811.06307v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1811.06307v1-abstract-full" style="display: none;"> The study of massive stars in different metallicity environments is a central topic of current stellar research. The spectral analysis of massive stars requires adequate model atmospheres. The computation of such models is difficult and time-consuming. Therefore, spectral analyses are greatly facilitated if they can refer to existing grids of models. Here we provide grids of model atmospheres for OB-type stars at metallicities corresponding to the Small and Large Magellanic Clouds, as well as to solar metallicity. In total, the grids comprise 785 individual models. The models were calculated using the state-of-the-art Potsdam Wolf-Rayet (PoWR) model atmosphere code. The parameter domain of the grids was set up using stellar evolution tracks. For all these models, we provide normalized and flux-calibrated spectra, spectral energy distributions, feedback parameters such as ionizing photons, Zanstra temperatures, and photometric magnitudes. The atmospheric structures (the density and temperature stratification) are available as well. All these data are publicly accessible through the PoWR website. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1811.06307v1-abstract-full').style.display = 'none'; document.getElementById('1811.06307v1-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> 15 November, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2018. </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">12 pages, 14 figures, 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 621, A85 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1807.04293">arXiv:1807.04293</a> <span> [<a href="https://arxiv.org/pdf/1807.04293">pdf</a>, <a href="https://arxiv.org/format/1807.04293">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/10.1051/0004-6361/201833712">10.1051/0004-6361/201833712 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Galactic WC and WO stars: The impact of revised distances from Gaia DR2 and their role as massive black hole progenitors </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=Hamann%2C+W">Wolf-Rainer Hamann</a>, <a href="/search/astro-ph?searchtype=author&query=Todt%2C+H">Helge Todt</a>, <a href="/search/astro-ph?searchtype=author&query=Hainich%2C+R">Rainer Hainich</a>, <a href="/search/astro-ph?searchtype=author&query=Shenar%2C+T">Tomer Shenar</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">Varsha Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L+M">Lidia M. Oskinova</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="1807.04293v3-abstract-short" style="display: inline;"> Wolf-Rayet stars of the carbon sequence (WC stars) are an important cornerstone in the late evolution of massive stars before their core collapse. As core-helium burning, hydrogen-free objects with huge mass-loss, they are likely the last observable stage before collapse and thus promising progenitor candidates for type Ib/c supernovae. Their strong mass-loss furthermore provides challenges and co… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1807.04293v3-abstract-full').style.display = 'inline'; document.getElementById('1807.04293v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1807.04293v3-abstract-full" style="display: none;"> Wolf-Rayet stars of the carbon sequence (WC stars) are an important cornerstone in the late evolution of massive stars before their core collapse. As core-helium burning, hydrogen-free objects with huge mass-loss, they are likely the last observable stage before collapse and thus promising progenitor candidates for type Ib/c supernovae. Their strong mass-loss furthermore provides challenges and constraints to the theory of radiatively driven winds. Thus, the determination of the WC star parameters is of major importance for several astrophysical fields. With Gaia DR2, for the first time parallaxes for a large sample of Galactic WC stars are available, removing major uncertainties inherent to earlier studies. In this work, we re-examine the sample from Sander et al. (2012) to derive key properties of the Galactic WC population. All quantities depending on the distance are updated, while the underlying spectral analyses remain untouched. Contrasting earlier assumptions, our study yields that WC stars of the same subtype can significantly vary in absolute magnitude. With Gaia DR2, the picture of the Galactic WC population becomes more complex: We obtain luminosities ranging from log L = 4.9 to 6.0 with one outlier having log L = 4.7. This indicates that the WC stars are likely formed from a broader initial mass range than previously assumed. We obtain mass-loss rates ranging between log Mdot = -5.1 and -4.1, with Mdot propto L^0.68 and a linear scaling of the modified wind momentum with luminosity. We discuss the implications for stellar evolution, including unsolved issues regarding the need of envelope inflation to address the WR radius problem, and the open questions in regard to the connection of WR stars with Gamma-ray bursts. WC and WO stars are progenitors of massive black holes, collapsing either silently or in a supernova that most-likely has to be preceded by a WO stage. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1807.04293v3-abstract-full').style.display = 'none'; document.getElementById('1807.04293v3-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 January, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 11 July, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2018. </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, 13 figures, 6 tables; A&A, v2: version in press</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 621, A92 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1805.00952">arXiv:1805.00952</a> <span> [<a href="https://arxiv.org/pdf/1805.00952">pdf</a>, <a href="https://arxiv.org/format/1805.00952">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/10.1051/0004-6361/201833006">10.1051/0004-6361/201833006 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Shortest-period Wolf-Rayet binary in the Small Magellanic Cloud: Part of a high-order multiple system </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=Hainich%2C+R">R. Hainich</a>, <a href="/search/astro-ph?searchtype=author&query=Todt%2C+H">H. Todt</a>, <a href="/search/astro-ph?searchtype=author&query=Moffat%2C+A+F+J">A. F. J. Moffat</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=Oskinova%2C+L+M">L. M. Oskinova</a>, <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">V. Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Munoz%2C+M">M. Munoz</a>, <a href="/search/astro-ph?searchtype=author&query=Pablo%2C+H">H. Pablo</a>, <a href="/search/astro-ph?searchtype=author&query=Sana%2C+H">H. Sana</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="1805.00952v1-abstract-short" style="display: inline;"> SMC AB 6 is the shortest-period (6.5d) Wolf-Rayet (WR) binary in the Small Magellanic Cloud, and is therefore crucial for the study of binary interaction and formation of WR stars at low metallicity. The WR component in AB 6 was previously found to be very luminous (logL=6.3[Lsun]) compared to its reported orbital mass (8Msun), placing it significantly above the Eddington limit. Through spectrosco… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1805.00952v1-abstract-full').style.display = 'inline'; document.getElementById('1805.00952v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1805.00952v1-abstract-full" style="display: none;"> SMC AB 6 is the shortest-period (6.5d) Wolf-Rayet (WR) binary in the Small Magellanic Cloud, and is therefore crucial for the study of binary interaction and formation of WR stars at low metallicity. The WR component in AB 6 was previously found to be very luminous (logL=6.3[Lsun]) compared to its reported orbital mass (8Msun), placing it significantly above the Eddington limit. Through spectroscopy and orbital analysis of newly acquired optical data taken with UVES, we aim to understand the peculiar results reported for this system and explore its evolutionary history. Results: We find that AB 6 contains at least four stars. The 6.5d period WR binary comprises the WR primary (WN3:h, star A) and a rather rapidly rotating early O-type companion (O5.5 V, star B). Static N and He lines suggest the presence of an emission line star (O5.5 I(f), star C). Finally, narrow absorption lines portraying a long-term radial velocity variation show the existence of a fourth star (O7.5 V, star D). Star D appears to form a second 140d period binary together with a fifth stellar member, which is a B-type dwarf or a black hole. It is not clear that these additional components are bound to the WR binary. The WR star is found to be less luminous than previously thought (logL = 5.9[Lsun]) and, adopting 41Msun for star B, more massive (18Msun). Correspondingly, the WR star does not exceed the Eddington limit. We derive the initial masses of 60 and 40Msun for stars A and B and an age of 3.9 Myr for the system. The WR binary likely experienced nonconservative mass transfer in the past supported by the relatively rapid rotation of star B. Conclusion: Our study shows that AB 6 is a multiple -- probably quintuple -- system. This finding resolves the previously reported puzzle of the WR primary exceeding the Eddington limit and suggests that the WR star exchanged mass with its companion in the past. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1805.00952v1-abstract-full').style.display = 'none'; document.getElementById('1805.00952v1-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, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2018. </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, 16 figures, accepted to A&A on the 30.4.2018. Comments welcome!</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 616, A103 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1802.07494">arXiv:1802.07494</a> <span> [<a href="https://arxiv.org/pdf/1802.07494">pdf</a>, <a href="https://arxiv.org/format/1802.07494">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/10.1051/0004-6361/201832816">10.1051/0004-6361/201832816 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Stellar population of the superbubble N206 in the LMC II. Parameters of the OB and WR stars, and the total massive star feedback </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">Varsha Ramachandran</a>, <a href="/search/astro-ph?searchtype=author&query=Hamann%2C+W+-">W. -R. Hamann</a>, <a href="/search/astro-ph?searchtype=author&query=Hainich%2C+R">R. Hainich</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=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=Gallagher%2C+J+S">J. S. Gallagher</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="1802.07494v2-abstract-short" style="display: inline;"> Clusters or associations of early-type stars are often associated with a 'superbubble' of hot gas. The formation of such superbubbles is caused by the feedback from massive stars. The complex N206 in the Large Magellanic Cloud exhibits a superbubble and a rich massive star population. We observed these massive stars using the FLAMES multi-object spectrograph at ESO-VLT. Available UV spectra from H… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1802.07494v2-abstract-full').style.display = 'inline'; document.getElementById('1802.07494v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1802.07494v2-abstract-full" style="display: none;"> Clusters or associations of early-type stars are often associated with a 'superbubble' of hot gas. The formation of such superbubbles is caused by the feedback from massive stars. The complex N206 in the Large Magellanic Cloud exhibits a superbubble and a rich massive star population. We observed these massive stars using the FLAMES multi-object spectrograph at ESO-VLT. Available UV spectra from HST, IUE, and FUSE are also used. The spectral analysis is performed with Potsdam Wolf-Rayet (PoWR) model atmospheres. We present the stellar and wind parameters of the OB stars and the two WR binaries in the N206 complex. Twelve percent of the sample show Oe/Be type emission lines, although most of them appear to rotate far below critical. We found eight runaway stars based on their radial velocity. The wind-momentum luminosity relation of our OB sample is consistent with the expectations. The HRD of the OB stars reveals a large age spread (1-30 Myr), suggesting different episodes of star formation in the complex. The youngest stars are concentrated in the inner part of the complex, while the older OB stars are scattered over outer regions. We derived the present day mass function for the entire N206 complex as well as for the cluster NGC2018. Three very massive Of stars are found to dominate the feedback among 164 OB stars in the sample. The two WR winds alone release about as much mechanical luminosity as the whole OB star sample. The cumulative mechanical feedback from all massive stellar winds is comparable to the combined mechanical energy of the supernova explosions that likely occurred in the complex. Accounting also for the WR wind and supernovae, the mechanical input over the last five Myr is ~$2.3\times10^{52}$ erg, which exceeds the current energy content of the complex by more than a factor of five. The morphology of the complex suggests a leakage of hot gas from the superbubble. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1802.07494v2-abstract-full').style.display = 'none'; document.getElementById('1802.07494v2-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, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 21 February, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2018. </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 615, A40 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1708.05088">arXiv:1708.05088</a> <span> [<a href="https://arxiv.org/pdf/1708.05088">pdf</a>, <a href="https://arxiv.org/format/1708.05088">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/10.1051/0004-6361/201731093">10.1051/0004-6361/201731093 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Stellar population of the superbubble N206 in the LMC I. Analysis of the Of-type stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Ramachandran%2C+V">Varsha Ramachandran</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=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=Todt%2C+H">H. Todt</a>, <a href="/search/astro-ph?searchtype=author&query=Gallagher%2C+J+S">J. S. Gallagher</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="1708.05088v2-abstract-short" style="display: inline;"> Massive stars are the key agents of feedback. Consequently, quantitative analysis of massive stars are required to understand how the feedback of these objects shapes/ creates the large scale structures of the ISM. The giant HII region N206 in the Large Magellanic Cloud contains an OB association that powers a X-ray superbubble, serving as an ideal laboratory in this context. We obtained optical s… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1708.05088v2-abstract-full').style.display = 'inline'; document.getElementById('1708.05088v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1708.05088v2-abstract-full" style="display: none;"> Massive stars are the key agents of feedback. Consequently, quantitative analysis of massive stars are required to understand how the feedback of these objects shapes/ creates the large scale structures of the ISM. The giant HII region N206 in the Large Magellanic Cloud contains an OB association that powers a X-ray superbubble, serving as an ideal laboratory in this context. We obtained optical spectra with the muti-object spectrograph FLAMES at the ESO-VLT. When possible, the optical spectroscopy was complemented by UV spectra from the HST, IUE, and FUSE archives. Detailed spectral classifications are presented for our sample Of-type stars. For the quantitative spectroscopic analysis we use the Potsdam Wolf-Rayet (PoWR) model atmosphere code. The physical parameters and nitrogen abundances of our sample stars are determined by fitting synthetic spectra to the observations. The stellar and wind parameters of nine Of-type stars are used to construct wind momentum,luminosity relationship. We find that our sample follows a relation close to the theoretical prediction, assuming clumped winds. The most massive star in the N206 association is an Of supergiant which has a very high mass-loss rate. Two objects in our sample reveal composite spectra, showing that the Of primaries have companions of late O subtype. All stars in our sample have an evolutionary age less than 4 million years, with the O2-type star being the youngest. All these stars show a systematic discrepancy between evolutionary and spectroscopic masses. All stars in our sample are nitrogen enriched. Nitrogen enrichment shows a clear correlation with increasing projected rotational velocities. The mechanical energy input from the Of stars alone is comparable to the energy stored in the N206 superbubble as measured from the observed X-ray and H alpha emission. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1708.05088v2-abstract-full').style.display = 'none'; document.getElementById('1708.05088v2-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 September, 2017; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 16 August, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2017. </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 the pubblication 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 609, A7 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1702.05629">arXiv:1702.05629</a> <span> [<a href="https://arxiv.org/pdf/1702.05629">pdf</a>, <a href="https://arxiv.org/ps/1702.05629">ps</a>, <a href="https://arxiv.org/format/1702.05629">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/S1743921317002563">10.1017/S1743921317002563 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Massive stars in advanced evolutionary stages, and the progenitor of GW150914 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Hamann%2C+W">Wolf-Rainer Hamann</a>, <a href="/search/astro-ph?searchtype=author&query=Oskinova%2C+L">Lidia Oskinova</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">Andreas Sander</a>, <a href="/search/astro-ph?searchtype=author&query=Hainich%2C+R">Rainer Hainich</a>, <a href="/search/astro-ph?searchtype=author&query=Shenar%2C+T">Tomer Shenar</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="1702.05629v1-abstract-short" style="display: inline;"> The recent discovery of a gravitational wave from the merging of two black holes of about 30 solar masses each challenges our incomplete understanding of massive stars and their evolution. Critical ingredients comprise mass-loss, rotation, magnetic fields, internal mixing, and mass transfer in close binary systems. The imperfect knowledge of these factors implies large uncertainties for models of… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1702.05629v1-abstract-full').style.display = 'inline'; document.getElementById('1702.05629v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1702.05629v1-abstract-full" style="display: none;"> The recent discovery of a gravitational wave from the merging of two black holes of about 30 solar masses each challenges our incomplete understanding of massive stars and their evolution. Critical ingredients comprise mass-loss, rotation, magnetic fields, internal mixing, and mass transfer in close binary systems. The imperfect knowledge of these factors implies large uncertainties for models of stellar populations and their feedback. In this contribution we summarize our empirical studies of Wolf-Rayet populations at different metallicities by means of modern non-LTE stellar atmosphere models, and confront these results with the predictions of stellar evolution models. At the metallicity of our Galaxy, stellar winds are probably too strong to leave remnant masses as high as 30 solar masses, but given the still poor agreement between evolutionary tracks and observation even this conclusion is debatable. At the low metallicity of the Small Magellanic Cloud, all WN stars which are (at least now) single are consistent with evolving quasi-homogeneously. O and B-type stars, in contrast, seem to comply with standard evolutionary models without strong internal mixing. Close binaries which avoided early merging could evolve quasi-homogeneously and lead to close compact remnants of relatively high masses that merge within a Hubble time. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1702.05629v1-abstract-full').style.display = 'none'; document.getElementById('1702.05629v1-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> 18 February, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2017. </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">5 pages, to be published in the Proceedings of the IAU Symposium No. 329 "The lives and death-throes of massive stars"</span> </p> </li> </ol> <div class="is-hidden-tablet">  <span class="help" style="display: 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