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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/2411.12815">arXiv:2411.12815</a> <span> [<a href="https://arxiv.org/pdf/2411.12815">pdf</a>, <a href="https://arxiv.org/format/2411.12815">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="Earth and Planetary Astrophysics">astro-ph.EP</span> <span class="tag is-small is-grey 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="Plasma Physics">physics.plasm-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> </div> </div> <p class="title is-5 mathjax"> Multi-Mission Observations of Relativistic Electrons and High-Speed Jets Linked to Shock Generated Transients </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Raptis%2C+S">Savvas Raptis</a>, <a href="/search/astro-ph?searchtype=author&query=Lindberg%2C+M">Martin Lindberg</a>, <a href="/search/astro-ph?searchtype=author&query=Liu%2C+T+Z">Terry Z. Liu</a>, <a href="/search/astro-ph?searchtype=author&query=Turner%2C+D+L">Drew L. Turner</a>, <a href="/search/astro-ph?searchtype=author&query=Lalti%2C+A">Ahmad Lalti</a>, <a href="/search/astro-ph?searchtype=author&query=Zhou%2C+Y">Yufei Zhou</a>, <a href="/search/astro-ph?searchtype=author&query=Kajdi%C4%8D%2C+P">Primo啪 Kajdi膷</a>, <a href="/search/astro-ph?searchtype=author&query=Kouloumvakos%2C+A">Athanasios Kouloumvakos</a>, <a href="/search/astro-ph?searchtype=author&query=Sibeck%2C+D+G">David G. Sibeck</a>, <a href="/search/astro-ph?searchtype=author&query=Vuorinen%2C+L">Laura Vuorinen</a>, <a href="/search/astro-ph?searchtype=author&query=Michael%2C+A">Adam Michael</a>, <a href="/search/astro-ph?searchtype=author&query=Shumko%2C+M">Mykhaylo Shumko</a>, <a href="/search/astro-ph?searchtype=author&query=Osmane%2C+A">Adnane Osmane</a>, <a href="/search/astro-ph?searchtype=author&query=Kr%C3%A4mer%2C+E">Eva Kr盲mer</a>, <a href="/search/astro-ph?searchtype=author&query=Turc%2C+L">Lucile Turc</a>, <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">Tomas Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Katsavrias%2C+C">Christos Katsavrias</a>, <a href="/search/astro-ph?searchtype=author&query=Wilson%2C+L+B">Lynn B. Wilson III</a>, <a href="/search/astro-ph?searchtype=author&query=Madanian%2C+H">Hadi Madanian</a>, <a href="/search/astro-ph?searchtype=author&query=Blanco-Cano%2C+X">X贸chitl Blanco-Cano</a>, <a href="/search/astro-ph?searchtype=author&query=Cohen%2C+I+J">Ian J. Cohen</a>, <a href="/search/astro-ph?searchtype=author&query=Escoubet%2C+C+P">C. Philippe Escoubet</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="2411.12815v1-abstract-short" style="display: inline;"> Shock-generated transients, such as hot flow anomalies (HFAs), upstream of planetary bow shocks, play a critical role in electron acceleration. Using multi-mission data from NASA's Magnetospheric Multiscale (MMS) and ESA's Cluster missions, we demonstrate the transmission of HFAs through Earth's quasi-parallel bow shock, associated with acceleration of electrons up to relativistic energies. Energe… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.12815v1-abstract-full').style.display = 'inline'; document.getElementById('2411.12815v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2411.12815v1-abstract-full" style="display: none;"> Shock-generated transients, such as hot flow anomalies (HFAs), upstream of planetary bow shocks, play a critical role in electron acceleration. Using multi-mission data from NASA's Magnetospheric Multiscale (MMS) and ESA's Cluster missions, we demonstrate the transmission of HFAs through Earth's quasi-parallel bow shock, associated with acceleration of electrons up to relativistic energies. Energetic electrons, initially accelerated upstream, are shown to remain broadly confined within the transmitted transient structures downstream, where betatron acceleration further boosts their energy due to elevated compression levels. Additionally, high-speed jets form at the compressive edges of HFAs, exhibiting a significant increase in dynamic pressure and potentially contributing to driving further localized compression. Our findings emphasize the efficiency of quasi-parallel shocks in driving particle acceleration far beyond the immediate shock transition region, expanding the acceleration region to a larger spatial domain. Finally, this study underscores the importance of multi-scale observational approach in understanding the convoluted processes behind collisionless shock physics and their broader implications. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.12815v1-abstract-full').style.display = 'none'; document.getElementById('2411.12815v1-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 November, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2405.18591">arXiv:2405.18591</a> <span> [<a href="https://arxiv.org/pdf/2405.18591">pdf</a>, <a href="https://arxiv.org/format/2405.18591">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="Plasma Physics">physics.plasm-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</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/10.3847/2041-8213/ad61da">10.3847/2041-8213/ad61da <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Large Scale Linear Magnetic Holes with Magnetic Mirror Properties in Hybrid Simulations of Solar Wind Turbulence </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Arr%C3%B2%2C+G">Giuseppe Arr貌</a>, <a href="/search/astro-ph?searchtype=author&query=Califano%2C+F">Francesco Califano</a>, <a href="/search/astro-ph?searchtype=author&query=Pucci%2C+F">Francesco Pucci</a>, <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">Tomas Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Li%2C+H">Hui Li</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="2405.18591v1-abstract-short" style="display: inline;"> Magnetic holes (MHs) are coherent magnetic field dips whose size ranges from fluid to kinetic scale, ubiquitously observed in the heliosphere and in planetary environments. Despite the longstanding effort in interpreting the abundance of observations, the origin and properties of MHs are still debated. In this letter, we investigate the interplay between plasma turbulence and MHs, using a 2D hybri… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.18591v1-abstract-full').style.display = 'inline'; document.getElementById('2405.18591v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2405.18591v1-abstract-full" style="display: none;"> Magnetic holes (MHs) are coherent magnetic field dips whose size ranges from fluid to kinetic scale, ubiquitously observed in the heliosphere and in planetary environments. Despite the longstanding effort in interpreting the abundance of observations, the origin and properties of MHs are still debated. In this letter, we investigate the interplay between plasma turbulence and MHs, using a 2D hybrid simulation initialized with solar wind parameters. We show that fully developed turbulence exhibits localized elongated magnetic depressions, whose properties are consistent with linear MHs frequently encountered in space. The observed MHs develop self-consistently from the initial magnetic field perturbations, by trapping hot ions with large pitch angles. Ion trapping produces an enhanced perpendicular temperature anysotropy that makes MHs stable for hundreds of ion gyroperiods, despite the surrounding turbulence. We introduce a new quantity, based on local magnetic field and ion temperature values, to measure the efficiency of ion trapping, with potential applications to the detection of MHs in satellite measurements. We complement this method by analyzing the ion velocity distribution functions inside MHs. Our diagnostics reveal the presence of trapped gyrotropic ion populations, whose velocity distribution is consistent with a loss cone, as expected for the motion of particles inside a magnetic mirror. Our results have potential implications for the theoretical and numerical modelling of MHs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.18591v1-abstract-full').style.display = 'none'; document.getElementById('2405.18591v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 28 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2312.05983">arXiv:2312.05983</a> <span> [<a href="https://arxiv.org/pdf/2312.05983">pdf</a>, <a href="https://arxiv.org/format/2312.05983">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="Space Physics">physics.space-ph</span> </div> </div> <p class="title is-5 mathjax"> Properties of an interplanetary shock observed at 0.07 and 0.7 Astronomical Units by Parker Solar Probe and Solar Orbiter </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Trotta%2C+D">D. Trotta</a>, <a href="/search/astro-ph?searchtype=author&query=Larosa%2C+A">A. Larosa</a>, <a href="/search/astro-ph?searchtype=author&query=Nicolaou%2C+G">G. Nicolaou</a>, <a href="/search/astro-ph?searchtype=author&query=Horbury%2C+T+S">T. S. Horbury</a>, <a href="/search/astro-ph?searchtype=author&query=Matteini%2C+L">L. Matteini</a>, <a href="/search/astro-ph?searchtype=author&query=Hietala%2C+H">H. Hietala</a>, <a href="/search/astro-ph?searchtype=author&query=Blanco-Cano%2C+X">X. Blanco-Cano</a>, <a href="/search/astro-ph?searchtype=author&query=Franci%2C+L">L. Franci</a>, <a href="/search/astro-ph?searchtype=author&query=Chen%2C+C+H+K">C. H. K. Chen</a>, <a href="/search/astro-ph?searchtype=author&query=Zhao%2C+L">L. Zhao</a>, <a href="/search/astro-ph?searchtype=author&query=Zank%2C+G+P">G. P. Zank</a>, <a href="/search/astro-ph?searchtype=author&query=Cohen%2C+C+M+S">C. M. S. Cohen</a>, <a href="/search/astro-ph?searchtype=author&query=Bale%2C+S+D">S. D. Bale</a>, <a href="/search/astro-ph?searchtype=author&query=Laker%2C+R">R. Laker</a>, <a href="/search/astro-ph?searchtype=author&query=Fargette%2C+N">N. Fargette</a>, <a href="/search/astro-ph?searchtype=author&query=Valentini%2C+F">F. Valentini</a>, <a href="/search/astro-ph?searchtype=author&query=Khotyaintsev%2C+Y">Y. Khotyaintsev</a>, <a href="/search/astro-ph?searchtype=author&query=Kieokaew%2C+R">R. Kieokaew</a>, <a href="/search/astro-ph?searchtype=author&query=Raouafi%2C+N">N. Raouafi</a>, <a href="/search/astro-ph?searchtype=author&query=Davies%2C+E">E. Davies</a>, <a href="/search/astro-ph?searchtype=author&query=Vainio%2C+R">R. Vainio</a>, <a href="/search/astro-ph?searchtype=author&query=Dresing%2C+N">N. Dresing</a>, <a href="/search/astro-ph?searchtype=author&query=Kilpua%2C+E">E. Kilpua</a>, <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">T. Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Owen%2C+C+J">C. J. Owen</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="2312.05983v1-abstract-short" style="display: inline;"> The Parker Solar Probe (PSP) and Solar Orbiter (SolO) missions opened a new observational window in the inner heliosphere, which is finally accessible to direct measurements. On September 05, 2022, a coronal mass ejection (CME)-driven interplanetary (IP) shock has been observed as close as 0.07 au by PSP. The CME then reached SolO, which was well radially-aligned at 0.7 au, thus providing us with… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.05983v1-abstract-full').style.display = 'inline'; document.getElementById('2312.05983v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2312.05983v1-abstract-full" style="display: none;"> The Parker Solar Probe (PSP) and Solar Orbiter (SolO) missions opened a new observational window in the inner heliosphere, which is finally accessible to direct measurements. On September 05, 2022, a coronal mass ejection (CME)-driven interplanetary (IP) shock has been observed as close as 0.07 au by PSP. The CME then reached SolO, which was well radially-aligned at 0.7 au, thus providing us with the opportunity to study the shock properties at so different heliocentric distances. We characterize the shock, investigate its typical parameters and compare its small-scale features at both locations. Using the PSP observations, we investigate how magnetic switchbacks and ion cyclotron waves are processed upon shock crossing. We find that switchbacks preserve their V--B correlation while compressed upon the shock passage, and that the signature of ion cyclotron waves disappears downstream of the shock. By contrast, the SolO observations reveal a very structured shock transition, with a population of shock-accelerated protons of up to about 2 MeV, showing irregularities in the shock downstream, which we correlate with solar wind structures propagating across the shock. At SolO, we also report the presence of low-energy ($\sim$ 100 eV) electrons scattering due to upstream shocklets. This study elucidates how the local features of IP shocks and their environments can be very different as they propagate through the heliosphere. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.05983v1-abstract-full').style.display = 'none'; document.getElementById('2312.05983v1-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, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 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">In review in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2308.09688">arXiv:2308.09688</a> <span> [<a href="https://arxiv.org/pdf/2308.09688">pdf</a>, <a href="https://arxiv.org/format/2308.09688">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/stad2108">10.1093/mnras/stad2108 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Modelling UX Ori Star Eclipses based on Spectral Observations with the Nordic Optical Telescope. I. RR Tau </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Grinin%2C+V+P">V. P. Grinin</a>, <a href="/search/astro-ph?searchtype=author&query=Tambovtseva%2C+L+V">L. V. Tambovtseva</a>, <a href="/search/astro-ph?searchtype=author&query=Djupvik%2C+A+A">A. A. Djupvik</a>, <a href="/search/astro-ph?searchtype=author&query=Gahm%2C+G">G. Gahm</a>, <a href="/search/astro-ph?searchtype=author&query=Grenman%2C+T">T. Grenman</a>, <a href="/search/astro-ph?searchtype=author&query=Weber%2C+H">H. Weber</a>, <a href="/search/astro-ph?searchtype=author&query=Bengtsson%2C+H">H. Bengtsson</a>, <a href="/search/astro-ph?searchtype=author&query=De+Angelis%2C+H">H. De Angelis</a>, <a href="/search/astro-ph?searchtype=author&query=Duszanowicz%2C+G">G. Duszanowicz</a>, <a href="/search/astro-ph?searchtype=author&query=Heinonen%2C+D">D. Heinonen</a>, <a href="/search/astro-ph?searchtype=author&query=Holmberg%2C+G">G. Holmberg</a>, <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">T. Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Larsson%2C+M">M. Larsson</a>, <a href="/search/astro-ph?searchtype=author&query=Warell%2C+J">J. Warell</a>, <a href="/search/astro-ph?searchtype=author&query=Wikander%2C+T">T. Wikander</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="2308.09688v1-abstract-short" style="display: inline;"> Based on observations obtained with the Nordic Optical Telescope we investigate the spectral variability of the Herbig Ae star RR Tau. This star belongs to the UX Ori family, characterized by very deep fadings caused by the screening of the star with opaque fragments (clouds) of the protoplanetary discs. At the moments of such minima one observes strong spectral variability due to the fact that th… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.09688v1-abstract-full').style.display = 'inline'; document.getElementById('2308.09688v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2308.09688v1-abstract-full" style="display: none;"> Based on observations obtained with the Nordic Optical Telescope we investigate the spectral variability of the Herbig Ae star RR Tau. This star belongs to the UX Ori family, characterized by very deep fadings caused by the screening of the star with opaque fragments (clouds) of the protoplanetary discs. At the moments of such minima one observes strong spectral variability due to the fact that the dust cloud occults, for an observer, not only the star but also a part of the region where the emission spectrum originates. We calculated a series of obscuration models to interpret the observed variability of the H-alpha line parameters. We consider two main obscuration scenarios: (1) the dust screen rises vertically above the circumstellar disc, and (2) the screen intersects the line-of-sight moving azimuthally with the disc. In both cases the model of the emission region consists of a compact magnetosphere and a magneto-centrifugal disc wind. Comparison with observations shows that the first scenario explains well the variability of the radiation flux, the equivalent width, as well as the asymmetry of the H-alpha line during eclipses, while the second scenario explains them only partly. This permits us to suggest that in the case of RR Tau, the main causes of the eclipses are either a structured disc wind, or the charged dust lifted along the field lines of the poloidal component of the magnetic field of the circumstellar disc. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.09688v1-abstract-full').style.display = 'none'; document.getElementById('2308.09688v1-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 August, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 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, 17 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> MNRAS 2023, 524, 4047 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2210.04734">arXiv:2210.04734</a> <span> [<a href="https://arxiv.org/pdf/2210.04734">pdf</a>, <a href="https://arxiv.org/format/2210.04734">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> <span class="tag is-small is-grey 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="Plasma Physics">physics.plasm-ph</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/10.1029/2022JA030754">10.1029/2022JA030754 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Mirror mode storms observed by Solar Orbiter </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Dimmock%2C+A+P">A. P. Dimmock</a>, <a href="/search/astro-ph?searchtype=author&query=Yordanova%2C+E">E. Yordanova</a>, <a href="/search/astro-ph?searchtype=author&query=Graham%2C+D+B">D. B. Graham</a>, <a href="/search/astro-ph?searchtype=author&query=Khotyaintsev%2C+Y+V">Yu. V. Khotyaintsev</a>, <a href="/search/astro-ph?searchtype=author&query=Blanco-Cano%2C+X">X. Blanco-Cano</a>, <a href="/search/astro-ph?searchtype=author&query=Kajdi%C4%8D%2C+P">P. Kajdi膷</a>, <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">T. Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Fedorov%2C+A">A. Fedorov</a>, <a href="/search/astro-ph?searchtype=author&query=Owen%2C+C+J">C. J. Owen</a>, <a href="/search/astro-ph?searchtype=author&query=Werner%2C+E+A+L+E">E. A. L. E. Werner</a>, <a href="/search/astro-ph?searchtype=author&query=Johlander%2C+A">A. Johlander</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="2210.04734v1-abstract-short" style="display: inline;"> Mirror modes are ubiquitous in space plasma and grow from pressure anisotropy. Together with other instabilities, they play a fundamental role in constraining the free energy contained in the plasma. This study focuses on mirror modes observed in the solar wind by Solar Orbiter for heliocentric distances between 0.5 and 1 AU. Typically, mirror modes have timescales from several to tens of seconds… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.04734v1-abstract-full').style.display = 'inline'; document.getElementById('2210.04734v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2210.04734v1-abstract-full" style="display: none;"> Mirror modes are ubiquitous in space plasma and grow from pressure anisotropy. Together with other instabilities, they play a fundamental role in constraining the free energy contained in the plasma. This study focuses on mirror modes observed in the solar wind by Solar Orbiter for heliocentric distances between 0.5 and 1 AU. Typically, mirror modes have timescales from several to tens of seconds and are considered quasi-MHD structures. In the solar wind, they also generally appear as isolated structures. However, in certain conditions, prolonged and bursty trains of higher frequency mirror modes are measured, which have been labeled previously as mirror mode storms. At present, only a handful of existing studies have focused on mirror mode storms, meaning that many open questions remain. In this study, Solar Orbiter has been used to investigate several key aspects of mirror mode storms: their dependence on heliocentric distance, association with local plasma properties, temporal/spatial scale, amplitude, and connections with larger-scale solar wind transients. The main results are that mirror mode storms often approach local ion scales and can no longer be treated as quasi-MHD, thus breaking the commonly used long-wavelength assumption. They are typically observed close to current sheets and downstream of interplanetary shocks. The events were observed during slow solar wind speeds and there was a tendency for higher occurrence closer to the Sun. The occurrence is low, so they do not play a fundamental role in regulating ambient solar wind but may play a larger role inside transients. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.04734v1-abstract-full').style.display = 'none'; document.getElementById('2210.04734v1-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 October, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2022. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2202.13243">arXiv:2202.13243</a> <span> [<a href="https://arxiv.org/pdf/2202.13243">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="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/10.1007/s11214-020-00712-8">10.1007/s11214-020-00712-8 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Investigating Mercury's Environment with the Two-Spacecraft BepiColombo Mission </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Milillo%2C+A">A. Milillo</a>, <a href="/search/astro-ph?searchtype=author&query=Fujimoto%2C+M">M. Fujimoto</a>, <a href="/search/astro-ph?searchtype=author&query=Murakami%2C+G">G. Murakami</a>, <a href="/search/astro-ph?searchtype=author&query=Benkhoff%2C+J">J. Benkhoff</a>, <a href="/search/astro-ph?searchtype=author&query=Zender%2C+J">J. Zender</a>, <a href="/search/astro-ph?searchtype=author&query=Aizawa%2C+S">S. Aizawa</a>, <a href="/search/astro-ph?searchtype=author&query=D%C3%B3sa%2C+M">M. D贸sa</a>, <a href="/search/astro-ph?searchtype=author&query=Griton%2C+L">L. Griton</a>, <a href="/search/astro-ph?searchtype=author&query=Heyner%2C+D">D. Heyner</a>, <a href="/search/astro-ph?searchtype=author&query=Ho%2C+G">G. Ho</a>, <a href="/search/astro-ph?searchtype=author&query=Imber%2C+S+M">S. M. Imber</a>, <a href="/search/astro-ph?searchtype=author&query=Jia%2C+X">X. Jia</a>, <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">T. Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Killen%2C+R+M">R. M. Killen</a>, <a href="/search/astro-ph?searchtype=author&query=Laurenza%2C+M">M. Laurenza</a>, <a href="/search/astro-ph?searchtype=author&query=Lindsay%2C+S+T">S. T. Lindsay</a>, <a href="/search/astro-ph?searchtype=author&query=McKenna-Lawlor%2C+S">S. McKenna-Lawlor</a>, <a href="/search/astro-ph?searchtype=author&query=Mura%2C+A">A. Mura</a>, <a href="/search/astro-ph?searchtype=author&query=Raines%2C+J+M">J. M. Raines</a>, <a href="/search/astro-ph?searchtype=author&query=Rothery%2C+D+A">D. A. Rothery</a>, <a href="/search/astro-ph?searchtype=author&query=Andr%C3%A9%2C+N">N. Andr茅</a>, <a href="/search/astro-ph?searchtype=author&query=Baumjohann%2C+W">W. Baumjohann</a>, <a href="/search/astro-ph?searchtype=author&query=Berezhnoy%2C+A">A. Berezhnoy</a>, <a href="/search/astro-ph?searchtype=author&query=Bourdin%2C+P+-">P. -A. Bourdin</a>, <a href="/search/astro-ph?searchtype=author&query=Bunce%2C+E+J">E. J. Bunce</a> , et al. (54 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="2202.13243v1-abstract-short" style="display: inline;"> The ESA-JAXA BepiColombo mission will provide simultaneous measurements from two spacecraft, offering an unprecedented opportunity to investigate magnetospheric and exospheric dynamics at Mercury as well as their interactions with the solar wind, radiation, and interplanetary dust. Many scientific instruments onboard the two spacecraft will be completely, or partially devoted to study the near-spa… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.13243v1-abstract-full').style.display = 'inline'; document.getElementById('2202.13243v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2202.13243v1-abstract-full" style="display: none;"> The ESA-JAXA BepiColombo mission will provide simultaneous measurements from two spacecraft, offering an unprecedented opportunity to investigate magnetospheric and exospheric dynamics at Mercury as well as their interactions with the solar wind, radiation, and interplanetary dust. Many scientific instruments onboard the two spacecraft will be completely, or partially devoted to study the near-space environment of Mercury as well as the complex processes that govern it. Many issues remain unsolved even after the MESSENGER mission that ended in 2015. The specific orbits of the two spacecraft, MPO and Mio, and the comprehensive scientific payload allow a wider range of scientific questions to be addressed than those that could be achieved by the individual instruments acting alone, or by previous missions. These joint observations are of key importance because many phenomena in Mercury's environment are highly temporally and spatially variable. Examples of possible coordinated observations are described in this article, analysing the required geometrical conditions, pointing, resolutions and operation timing of different BepiColombo instruments sensors. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.13243v1-abstract-full').style.display = 'none'; document.getElementById('2202.13243v1-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, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">78 pages, 14 figures, published</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Space Science Reviews (2020), Volume 216, Issue 5, article id.93 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2106.15747">arXiv:2106.15747</a> <span> [<a href="https://arxiv.org/pdf/2106.15747">pdf</a>, <a href="https://arxiv.org/ps/2106.15747">ps</a>, <a href="https://arxiv.org/format/2106.15747">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Plasma Physics">physics.plasm-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</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/10.1029/2021GL093173">10.1029/2021GL093173 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Causes of jets in the quasi-perpendicular magnetosheath </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kajdi%C4%8D%2C+P">Primo啪 Kajdi膷</a>, <a href="/search/astro-ph?searchtype=author&query=Raptis%2C+S">Savvas Raptis</a>, <a href="/search/astro-ph?searchtype=author&query=Blanco-Cano%2C+X">X贸chitl Blanco-Cano</a>, <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">Tomas Karlsson</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="2106.15747v1-abstract-short" style="display: inline;"> Magnetosheath jets are currently an important topic in the field of magnetosheath physics. It is thought that 97~\% of the jets are produced by the shock rippling at quasi-parallel shocks. Recently, large statistical studies of magnetosheath jets have been performed, however it is not clear whether rippling also produces jets found downstream of quasi-perpendicular shocks. We analyze four types of… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.15747v1-abstract-full').style.display = 'inline'; document.getElementById('2106.15747v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2106.15747v1-abstract-full" style="display: none;"> Magnetosheath jets are currently an important topic in the field of magnetosheath physics. It is thought that 97~\% of the jets are produced by the shock rippling at quasi-parallel shocks. Recently, large statistical studies of magnetosheath jets have been performed, however it is not clear whether rippling also produces jets found downstream of quasi-perpendicular shocks. We analyze four types of events in the quasi-perpendicular magnetosheath with signatures characteristic of magnetosheath jets, namely increased density and/or dynamic pressure, that were not produced by the shock rippling: 1) magnetic flux tubes connected to the quasi-parallel bow-shock, 2) non-reconnecting current sheets, 3) reconnection exhausts and 4) mirror mode waves. The flux tubes are downstream equivalents of the upstream traveling foreshocks. Magnetosheath jets can impact the magnetopause, so knowing the conditions under which they form may enable us to understand their signatures in the magnetosphere. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.15747v1-abstract-full').style.display = 'none'; document.getElementById('2106.15747v1-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 June, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 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 Geophysical Research Letters</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1911.05068">arXiv:1911.05068</a> <span> [<a href="https://arxiv.org/pdf/1911.05068">pdf</a>, <a href="https://arxiv.org/format/1911.05068">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="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/10.3847/1538-3881/ab570f">10.3847/1538-3881/ab570f <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Vanishing & Appearing Sources during a Century of Observations project: I. USNO objects missing in modern sky surveys and follow-up observations of a "missing star" </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Villarroel%2C+B">Beatriz Villarroel</a>, <a href="/search/astro-ph?searchtype=author&query=Soodla%2C+J">Johan Soodla</a>, <a href="/search/astro-ph?searchtype=author&query=Comer%C3%B3n%2C+S">S茅bastien Comer贸n</a>, <a href="/search/astro-ph?searchtype=author&query=Mattsson%2C+L">Lars Mattsson</a>, <a href="/search/astro-ph?searchtype=author&query=Pelckmans%2C+K">Kristiaan Pelckmans</a>, <a href="/search/astro-ph?searchtype=author&query=L%C3%B3pez-Corredoira%2C+M">Mart铆n L贸pez-Corredoira</a>, <a href="/search/astro-ph?searchtype=author&query=Krisciunas%2C+K">Kevin Krisciunas</a>, <a href="/search/astro-ph?searchtype=author&query=Guerras%2C+E">Eduardo Guerras</a>, <a href="/search/astro-ph?searchtype=author&query=Kochukhov%2C+O">Oleg Kochukhov</a>, <a href="/search/astro-ph?searchtype=author&query=Bergstedt%2C+J">Josefine Bergstedt</a>, <a href="/search/astro-ph?searchtype=author&query=Buelens%2C+B">Bart Buelens</a>, <a href="/search/astro-ph?searchtype=author&query=B%C3%A4r%2C+R+E">Rudolf E. B盲r</a>, <a href="/search/astro-ph?searchtype=author&query=Cubo%2C+R">Rub茅n Cubo</a>, <a href="/search/astro-ph?searchtype=author&query=Enriquez%2C+J+E">J. Emilio Enriquez</a>, <a href="/search/astro-ph?searchtype=author&query=Gupta%2C+A+C">Alok C. Gupta</a>, <a href="/search/astro-ph?searchtype=author&query=Imaz%2C+I">I帽igo Imaz</a>, <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">Torgny Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Prieto%2C+M+A">M. Almudena Prieto</a>, <a href="/search/astro-ph?searchtype=author&query=Shlyapnikov%2C+A+A">Aleksey A. Shlyapnikov</a>, <a href="/search/astro-ph?searchtype=author&query=de+Souza%2C+R+S">Rafael S. de Souza</a>, <a href="/search/astro-ph?searchtype=author&query=Vavilova%2C+I+B">Irina B. Vavilova</a>, <a href="/search/astro-ph?searchtype=author&query=Ward%2C+M+J">Martin J. Ward</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="1911.05068v2-abstract-short" style="display: inline;"> In this paper we report the current status of a new research program. The primary goal of the "Vanishing & Appearing Sources during a Century of Observations" (VASCO) project is to search for vanishing and appearing sources using existing survey data to find examples of exceptional astrophysical transients. The implications of finding such objects extend from traditional astrophysics fields to the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1911.05068v2-abstract-full').style.display = 'inline'; document.getElementById('1911.05068v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1911.05068v2-abstract-full" style="display: none;"> In this paper we report the current status of a new research program. The primary goal of the "Vanishing & Appearing Sources during a Century of Observations" (VASCO) project is to search for vanishing and appearing sources using existing survey data to find examples of exceptional astrophysical transients. The implications of finding such objects extend from traditional astrophysics fields to the more exotic searches for evidence of technologically advanced civilizations. In this first paper we present new, deeper observations of the tentative candidate discovered by Villarroel et al. (2016). We then perform the first searches for vanishing objects throughout the sky by comparing 600 million objects from the US Naval Observatory Catalogue (USNO) B1.0 down to a limiting magnitude of $\sim 20 - 21$ with the recent Pan-STARRS Data Release-1 (DR1) with a limiting magnitude of $\sim$ 23.4. We find about 150,000 preliminary candidates that do not have any Pan-STARRS counterpart within a 30 arcsec radius. We show that these objects are redder and have larger proper motions than typical USNO objects. We visually examine the images for a subset of about 24,000 candidates, superseding the 2016 study with a sample ten times larger. We find about $\sim$ 100 point sources visible in only one epoch in the red band of the USNO which may be of interest in searches for strong M dwarf flares, high-redshift supernovae or other catagories of unidentified red transients. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1911.05068v2-abstract-full').style.display = 'none'; document.getElementById('1911.05068v2-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, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 12 November, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 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">SETI meets time domain astronomy. Accepted into the Astronomical Journal</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1908.00377">arXiv:1908.00377</a> <span> [<a href="https://arxiv.org/pdf/1908.00377">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> </div> </div> <p class="title is-5 mathjax"> Cometary Plasma Science -- A White Paper in response to the Voyage 2050 Call by the European Space Agency </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=G%C3%B6tz%2C+C">Charlotte G枚tz</a>, <a href="/search/astro-ph?searchtype=author&query=Gunell%2C+H">Herber Gunell</a>, <a href="/search/astro-ph?searchtype=author&query=Volwerk%2C+M">Martin Volwerk</a>, <a href="/search/astro-ph?searchtype=author&query=Beth%2C+A">Arnaud Beth</a>, <a href="/search/astro-ph?searchtype=author&query=Eriksson%2C+A">Anders Eriksson</a>, <a href="/search/astro-ph?searchtype=author&query=Galand%2C+M">Marina Galand</a>, <a href="/search/astro-ph?searchtype=author&query=Henri%2C+P">Pierre Henri</a>, <a href="/search/astro-ph?searchtype=author&query=Nilsson%2C+H">Hans Nilsson</a>, <a href="/search/astro-ph?searchtype=author&query=Wedlund%2C+C+S">Cyril Simon Wedlund</a>, <a href="/search/astro-ph?searchtype=author&query=Alho%2C+M">Markku Alho</a>, <a href="/search/astro-ph?searchtype=author&query=Andersson%2C+L">Laila Andersson</a>, <a href="/search/astro-ph?searchtype=author&query=Andre%2C+N">Nicolas Andre</a>, <a href="/search/astro-ph?searchtype=author&query=De+Keyser%2C+J">Johan De Keyser</a>, <a href="/search/astro-ph?searchtype=author&query=Deca%2C+J">Jan Deca</a>, <a href="/search/astro-ph?searchtype=author&query=Ge%2C+Y">Yasong Ge</a>, <a href="/search/astro-ph?searchtype=author&query=Gla%C3%9Fmeier%2C+K">Karl-Heinz Gla脽meier</a>, <a href="/search/astro-ph?searchtype=author&query=Hajra%2C+R">Rajkumar Hajra</a>, <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">Tomas Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Kasahara%2C+S">Satoshi Kasahara</a>, <a href="/search/astro-ph?searchtype=author&query=Kolmasova%2C+I">Ivana Kolmasova</a>, <a href="/search/astro-ph?searchtype=author&query=LLera%2C+K">Kristie LLera</a>, <a href="/search/astro-ph?searchtype=author&query=Madanian%2C+H">Hadi Madanian</a>, <a href="/search/astro-ph?searchtype=author&query=Mann%2C+I">Ingrid Mann</a>, <a href="/search/astro-ph?searchtype=author&query=Mazelle%2C+C">Christian Mazelle</a>, <a href="/search/astro-ph?searchtype=author&query=Odelstad%2C+E">Elias Odelstad</a> , et al. (5 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="1908.00377v1-abstract-short" style="display: inline;"> Comets hold the key to the understanding of our solar system, its formation and its evolution, and to the fundamental plasma processes at work both in it and beyond it. A comet nucleus emits gas as it is heated by the sunlight. The gas forms the coma, where it is ionised, becomes a plasma and eventually interacts with the solar wind. Besides these neutral and ionised gases, the coma also contains… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1908.00377v1-abstract-full').style.display = 'inline'; document.getElementById('1908.00377v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1908.00377v1-abstract-full" style="display: none;"> Comets hold the key to the understanding of our solar system, its formation and its evolution, and to the fundamental plasma processes at work both in it and beyond it. A comet nucleus emits gas as it is heated by the sunlight. The gas forms the coma, where it is ionised, becomes a plasma and eventually interacts with the solar wind. Besides these neutral and ionised gases, the coma also contains dust grains, released from the comet nucleus. As a cometary atmosphere develops when the comet travels through the solar system, large-scale structures, such as the plasma boundaries, develop and disappear, while at planets such large-scale structures are only accessible in their fully grown, quasi-steady state. In situ measurements at comets enable us to learn both how such large-scale structures are formed or reformed and how small-scale processes in the plasma affect the formation and properties of these large scale structures. Furthermore, a comet goes through a wide range of parameter regimes during its life cycle, where either collisional processes, involving neutrals and charged particles, or collisionless processes are at play, and might even compete in complicated transitional regimes. Thus a comet presents a unique opportunity to study this parameter space, from an asteroid-like to a Mars- and Venus-like interaction. Fast flybys of comets have made many new discoveries, setting the stage for a multi-spacecraft mission to accompany a comet on its journey through the solar system. This white paper reviews the present-day knowledge of cometary plasmas, discusses the many questions that remain unanswered, and outlines a multi-spacecraft ESA mission to accompany a comet that will answer these questions by combining both multi-spacecraft observations and a rendezvous mission, and at the same time advance our understanding of fundamental plasma physics and its role in planetary systems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1908.00377v1-abstract-full').style.display = 'none'; document.getElementById('1908.00377v1-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 August, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2019. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1705.08725">arXiv:1705.08725</a> <span> [<a href="https://arxiv.org/pdf/1705.08725">pdf</a>, <a href="https://arxiv.org/format/1705.08725">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</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/10.1051/0004-6361/201630159">10.1051/0004-6361/201630159 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Cold and warm electrons at comet 67P </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Eriksson%2C+A+I">A. I. Eriksson</a>, <a href="/search/astro-ph?searchtype=author&query=Engelhardt%2C+I+A+D">I. A. D. Engelhardt</a>, <a href="/search/astro-ph?searchtype=author&query=Andre%2C+M">M. Andre</a>, <a href="/search/astro-ph?searchtype=author&query=Bostrom%2C+R">R. Bostrom</a>, <a href="/search/astro-ph?searchtype=author&query=Edberg%2C+N+J+T">N. J. T. Edberg</a>, <a href="/search/astro-ph?searchtype=author&query=Johansson%2C+F+L">F. L. Johansson</a>, <a href="/search/astro-ph?searchtype=author&query=Odelstad%2C+E">E. Odelstad</a>, <a href="/search/astro-ph?searchtype=author&query=Vigren%2C+E">E. Vigren</a>, <a href="/search/astro-ph?searchtype=author&query=Wahlund%2C+J+-">J. -E. Wahlund</a>, <a href="/search/astro-ph?searchtype=author&query=Henri%2C+P">P. Henri</a>, <a href="/search/astro-ph?searchtype=author&query=Lebreton%2C+J+-">J. -P. Lebreton</a>, <a href="/search/astro-ph?searchtype=author&query=Miloch%2C+W+J">W. J. Miloch</a>, <a href="/search/astro-ph?searchtype=author&query=Paulsson%2C+J+J+P">J. J. P. Paulsson</a>, <a href="/search/astro-ph?searchtype=author&query=Wedlund%2C+C+S">C. Simon Wedlund</a>, <a href="/search/astro-ph?searchtype=author&query=Yang%2C+L">L. Yang</a>, <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">T. Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Jarvinen%2C+R">R. Jarvinen</a>, <a href="/search/astro-ph?searchtype=author&query=Broiles%2C+T">T. Broiles</a>, <a href="/search/astro-ph?searchtype=author&query=Mandt%2C+K">K. Mandt</a>, <a href="/search/astro-ph?searchtype=author&query=Carr%2C+C+M">C. M. Carr</a>, <a href="/search/astro-ph?searchtype=author&query=Galand%2C+M">M. Galand</a>, <a href="/search/astro-ph?searchtype=author&query=Nilsson%2C+H">H. Nilsson</a>, <a href="/search/astro-ph?searchtype=author&query=Norberg%2C+C">C. Norberg</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="1705.08725v1-abstract-short" style="display: inline;"> Strong electron cooling on the neutral gas in cometary comae has been predicted for a long time, but actual measurements of low electron temperature are scarce. We present in situ measurements of plasma density, electron temperature and spacecraft potential by the Rosetta Langmuir probe instrument, LAP. Data acquired within a few hundred km from the nucleus are dominated by a warm component with e… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1705.08725v1-abstract-full').style.display = 'inline'; document.getElementById('1705.08725v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1705.08725v1-abstract-full" style="display: none;"> Strong electron cooling on the neutral gas in cometary comae has been predicted for a long time, but actual measurements of low electron temperature are scarce. We present in situ measurements of plasma density, electron temperature and spacecraft potential by the Rosetta Langmuir probe instrument, LAP. Data acquired within a few hundred km from the nucleus are dominated by a warm component with electron temperature typically 5--10 eV at all heliocentric distances covered (1.25 to 3.83 AU). A cold component, with temperature no higher than about 0.1 eV, appears in the data as short (few to few tens of seconds) pulses of high probe current, indicating local enhancement of plasma density as well as a decrease in electron temperature. These pulses first appeared around 3 AU and were seen for longer periods close to perihelion. The general pattern of pulse appearance follows that of neutral gas and plasma density. We have not identified any periods with only cold electrons present. The electron flux to Rosetta was always dominated by higher energies, driving the spacecraft potential to order -10 V. The warm (5--10 eV) electron population is interpreted as electrons retaining the energy they obtained when released in the ionisation process. The sometimes observed cold populations with electron temperatures below 0.1 eV verify collisional cooling in the coma. The cold electrons were only observed together with the warm population. The general appearance of the cold population appears to be consistent with a Haser-like model, implicitly supporting also the coupling of ions to the neutral gas. The expanding cold plasma is unstable, forming filaments that we observe as pulses. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1705.08725v1-abstract-full').style.display = 'none'; document.getElementById('1705.08725v1-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 May, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astronomy and Astrophysics (2016) 30159 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1701.08647">arXiv:1701.08647</a> <span> [<a href="https://arxiv.org/pdf/1701.08647">pdf</a>, <a href="https://arxiv.org/ps/1701.08647">ps</a>, <a href="https://arxiv.org/format/1701.08647">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> </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/aa5d5a">10.3847/1538-4357/aa5d5a <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> AGN luminosity and stellar age -- two missing ingredients for AGN unification as seen with iPTF supernovae </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Villarroel%2C+B">Beatriz Villarroel</a>, <a href="/search/astro-ph?searchtype=author&query=Nyholm%2C+A">Anders Nyholm</a>, <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">Torgny Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Comer%C3%B3n%2C+S">S茅bastien Comer贸n</a>, <a href="/search/astro-ph?searchtype=author&query=Korn%2C+A">Andreas Korn</a>, <a href="/search/astro-ph?searchtype=author&query=Sollerman%2C+J">Jesper Sollerman</a>, <a href="/search/astro-ph?searchtype=author&query=Zackrisson%2C+E">Erik Zackrisson</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="1701.08647v1-abstract-short" style="display: inline;"> Active Galactic Nuclei (AGN) are extremely powerful cosmic objects, driven by accretion of hot gas upon super-massive black holes. The zoo of AGN classes are divided into two major groups, with Type-1 AGN displaying broad Balmer emission lines and Type-2 narrow ones. For a long time it was believed that a Type-2 AGN is a Type-1 AGN viewed through a dusty kiloparsec-size torus, but an emerging body… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1701.08647v1-abstract-full').style.display = 'inline'; document.getElementById('1701.08647v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1701.08647v1-abstract-full" style="display: none;"> Active Galactic Nuclei (AGN) are extremely powerful cosmic objects, driven by accretion of hot gas upon super-massive black holes. The zoo of AGN classes are divided into two major groups, with Type-1 AGN displaying broad Balmer emission lines and Type-2 narrow ones. For a long time it was believed that a Type-2 AGN is a Type-1 AGN viewed through a dusty kiloparsec-size torus, but an emerging body of observations suggests more than just the viewing angle matters. Here we report significant differences in supernova counts and classes in the first study to date of supernovae near Type-1 and Type-2 AGN host galaxies, using data from the intermediate Palomar Transient Factory, the Sloan Digital Sky Survey Data Release 7 and Galaxy Zoo. We detect many more supernovae in Type-2 AGN hosts (size of effect $\sim$ 5.1$蟽$) compared to Type-1 hosts, which shows that the two classes of AGN are located inside host galaxies with different properties. In addition, Type-1 and Type-2 AGN that are dominated by star formation according to WISE colours $m_{W1} - m_{W2} < 0.5$ and are matched in 22 $渭$m absolute magnitude differ by a factor of ten in $L$[OIII]$位$5007 luminosity, suggesting that when residing in similar type of host galaxies Type-1 AGN are much more luminous. Our results demonstrate two more factors that play an important role in completing the current picture: the age of stellar populations and the AGN luminosity. This has immediate consequences for understanding the many AGN classes and galaxy evolution. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1701.08647v1-abstract-full').style.display = 'none'; document.getElementById('1701.08647v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 30 January, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 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 to the Astrophysical Journal (ApJ)</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1603.05006">arXiv:1603.05006</a> <span> [<a href="https://arxiv.org/pdf/1603.05006">pdf</a>, <a href="https://arxiv.org/ps/1603.05006">ps</a>, <a href="https://arxiv.org/format/1603.05006">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</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/10.1051/0004-6361/201528041">10.1051/0004-6361/201528041 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Isotopic ratios of H, C, N, O, and S in comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy) </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Biver%2C+N">N. Biver</a>, <a href="/search/astro-ph?searchtype=author&query=Moreno%2C+R">R. Moreno</a>, <a href="/search/astro-ph?searchtype=author&query=Bockel%C3%A9e-Morvan%2C+D">D. Bockel茅e-Morvan</a>, <a href="/search/astro-ph?searchtype=author&query=Sandqvist%2C+A">Aa. Sandqvist</a>, <a href="/search/astro-ph?searchtype=author&query=Colom%2C+P">P. Colom</a>, <a href="/search/astro-ph?searchtype=author&query=Crovisier%2C+J">J. Crovisier</a>, <a href="/search/astro-ph?searchtype=author&query=Lis%2C+D+C">D. C. Lis</a>, <a href="/search/astro-ph?searchtype=author&query=Boissier%2C+J">J. Boissier</a>, <a href="/search/astro-ph?searchtype=author&query=Debout%2C+V">V. Debout</a>, <a href="/search/astro-ph?searchtype=author&query=Paubert%2C+G">G. Paubert</a>, <a href="/search/astro-ph?searchtype=author&query=Milam%2C+S">S. Milam</a>, <a href="/search/astro-ph?searchtype=author&query=Hjalmarson%2C+A">A. Hjalmarson</a>, <a href="/search/astro-ph?searchtype=author&query=Lundin%2C+S">S. Lundin</a>, <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">T. Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Battelino%2C+M">M. Battelino</a>, <a href="/search/astro-ph?searchtype=author&query=Frisk%2C+U">U. Frisk</a>, <a href="/search/astro-ph?searchtype=author&query=Murtagh%2C+D">D. Murtagh</a>, <a href="/search/astro-ph?searchtype=author&query=team%2C+t+O">the Odin team</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="1603.05006v1-abstract-short" style="display: inline;"> The apparition of bright comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy) in March-April 2013 and January 2015, combined with the improved observational capabilities of submillimeter facilities, offered an opportunity to carry out sensitive compositional and isotopic studies of the volatiles in their coma. We observed comet Lovejoy with the IRAM 30m telescope between 13 and 26 January 2015, and w… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1603.05006v1-abstract-full').style.display = 'inline'; document.getElementById('1603.05006v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1603.05006v1-abstract-full" style="display: none;"> The apparition of bright comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy) in March-April 2013 and January 2015, combined with the improved observational capabilities of submillimeter facilities, offered an opportunity to carry out sensitive compositional and isotopic studies of the volatiles in their coma. We observed comet Lovejoy with the IRAM 30m telescope between 13 and 26 January 2015, and with the Odin submillimeter space observatory on 29 January - 3 February 2015. We detected 22 molecules and several isotopologues. The H$_2^{16}$O and H$_2^{18}$O production rates measured with Odin follow a periodic pattern with a period of 0.94 days and an amplitude of ~25%. The inferred isotope ratios in comet Lovejoy are $^{16}$O/$^{18}$O = 499 $\pm$ 24 and D/H = 1.4 $\pm$ 0.4 $\times 10^{-4}$ in water, $^{32}$S/$^{34}$S = 24.7 $\pm$ 3.5 in CS, all compatible with terrestrial values. The ratio $^{12}$C/$^{13}$C = 109 $\pm$ 14 in HCN is marginally higher than terrestrial and $^{14}$N/$^{15}$N = 145 $\pm$ 12 in HCN is half the Earth ratio. Several upper limits for D/H or 12C/13C in other molecules are reported. From our observation of HDO in comet C/2014 Q2 (Lovejoy), we report the first D/H ratio in an Oort Cloud comet that is not larger than the terrestrial value. On the other hand, the observation of the same HDO line in the other Oort-cloud comet, C/2012 F6 (Lemmon), suggests a D/H value four times higher. Given the previous measurements of D/H in cometary water, this illustrates that a diversity in the D/H ratio and in the chemical composition, is present even within the same dynamical group of comets, suggesting that current dynamical groups contain comets formed at very different places or times in the early solar system. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1603.05006v1-abstract-full').style.display = 'none'; document.getElementById('1603.05006v1-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 March, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2016. </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 and Astrophysics</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 589, A78 (2016) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1308.0150">arXiv:1308.0150</a> <span> [<a href="https://arxiv.org/pdf/1308.0150">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> </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/10.1016/j.actaastro.2014.05.027">10.1016/j.actaastro.2014.05.027 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Flight demonstration of formation flying capabilities for future missions (NEAT Pathfinder) </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Delpech%2C+M">M. Delpech</a>, <a href="/search/astro-ph?searchtype=author&query=Malbet%2C+F">F. Malbet</a>, <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">T. Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Larsson%2C+R">R. Larsson</a>, <a href="/search/astro-ph?searchtype=author&query=L%C3%A9ger%2C+A">A. L茅ger</a>, <a href="/search/astro-ph?searchtype=author&query=Jorgensen%2C+J">J. Jorgensen</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="1308.0150v1-abstract-short" style="display: inline;"> PRISMA is a demonstration mission for formation-flying and on-orbit-servicing critical technologies that involves two spacecraft launched in low Earth orbit in June 2010 and still in operation. Funded by the Swedish National Space Board, PRISMA mission has been developed by OHB Sweden with important contributions from the German Aerospace Centre (DLR/GSOC), the French Space Agency (CNES), and the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1308.0150v1-abstract-full').style.display = 'inline'; document.getElementById('1308.0150v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1308.0150v1-abstract-full" style="display: none;"> PRISMA is a demonstration mission for formation-flying and on-orbit-servicing critical technologies that involves two spacecraft launched in low Earth orbit in June 2010 and still in operation. Funded by the Swedish National Space Board, PRISMA mission has been developed by OHB Sweden with important contributions from the German Aerospace Centre (DLR/GSOC), the French Space Agency (CNES), and the Technical University of Denmark (DTU). The paper focuses on the last CNES experiment achieved in September 2012 that was devoted to the preparation of future astrometry missions illustrated by the NEAT and microNEAT mission concepts. The experiment consisted in performing the type of formation maneuvers required to point the two-satellite axis to a celestial target and maintain it fixed during the observation period. Achieving inertial pointing for a LEO formation represented a new challenge given the numerous constraints from propellant usage to star tracker blinding. The paper presents the experiment objectives in relation with the NEAT/microNEAT mission concept, describes its main design features along with the guidance and control algorithms evolutions and discusses the results in terms of performances achieved during the two rehearsals <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1308.0150v1-abstract-full').style.display = 'none'; document.getElementById('1308.0150v1-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 August, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2013. </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, in Proc. of the 7th International Workshop on "Satellite Constellation and Formation Flying" held in Lisbon (Portugal), 13-15 March 2013</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1202.3815">arXiv:1202.3815</a> <span> [<a href="https://arxiv.org/pdf/1202.3815">pdf</a>, <a href="https://arxiv.org/ps/1202.3815">ps</a>, <a href="https://arxiv.org/format/1202.3815">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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> <p class="title is-5 mathjax"> A Relic Star Cluster in the Sextans Dwarf Spheroidal Galaxy - Implications for Early Star and Galaxy Formation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">Torgny Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Bland-Hawthorn%2C+J">Joss Bland-Hawthorn</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="1202.3815v1-abstract-short" style="display: inline;"> We present tentative evidence for the existence of a dissolved star cluster in the Sextans dwarf spheroidal galaxy. In a sample of six stars, we identify three (possibly four) stars around [Fe/H] =-2.7 that are highly clustered in a multi-dimensional chemical abundance space. The estimated initial stellar mass of the cluster is M*,init = 1.9^+1.5_-0.9 (1.6^+1.2_-0.8)*10^5 Msol assuming a Salpeter… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1202.3815v1-abstract-full').style.display = 'inline'; document.getElementById('1202.3815v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1202.3815v1-abstract-full" style="display: none;"> We present tentative evidence for the existence of a dissolved star cluster in the Sextans dwarf spheroidal galaxy. In a sample of six stars, we identify three (possibly four) stars around [Fe/H] =-2.7 that are highly clustered in a multi-dimensional chemical abundance space. The estimated initial stellar mass of the cluster is M*,init = 1.9^+1.5_-0.9 (1.6^+1.2_-0.8)*10^5 Msol assuming a Salpeter (Kroupa) initial mass function (IMF). If corroborated by follow-up spectroscopy, this ancient star cluster at [Fe/H] =-2.7 is the most metal-poor system identified to date. Inspired by this finding, we also present a new way to interpret the cumulative metallicity functions of dwarf galaxies. From available observational data, we speculate that the ultra-faint dwarf galaxy population, or a significant fraction thereof, and the more luminous, classical dwarf spheroidal population were formed in different environments and would thus be distinct in origin. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1202.3815v1-abstract-full').style.display = 'none'; document.getElementById('1202.3815v1-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 February, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2012. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">4 pages, 2 figures, to appear in the ASP Conf. Ser. on Galactic Archaeology: Near-Field Cosmology and the Formation of the Milky Way (3rd Subaru International Conference)</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1201.5376">arXiv:1201.5376</a> <span> [<a href="https://arxiv.org/pdf/1201.5376">pdf</a>, <a href="https://arxiv.org/ps/1201.5376">ps</a>, <a href="https://arxiv.org/format/1201.5376">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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/10.1088/0004-637X/759/2/111">10.1088/0004-637X/759/2/111 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Chemical Signature of a Relic Star Cluster in the Sextans Dwarf Spheroidal Galaxy - Implications for Near-Field Cosmology </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">Torgny Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Bland-Hawthorn%2C+J">Joss Bland-Hawthorn</a>, <a href="/search/astro-ph?searchtype=author&query=Freeman%2C+K">Ken Freeman</a>, <a href="/search/astro-ph?searchtype=author&query=Silk%2C+J">Joe Silk</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="1201.5376v2-abstract-short" style="display: inline;"> We present tentative evidence for the existence of a dissolved star cluster at [Fe/H]=-2.7 in the Sextans dwarf spheroidal galaxy. We use the technique of chemical tagging to identify stars that are highly clustered in a multi-dimensional chemical abundance space (C-space). In a sample of six stars, three, possibly four stars are identified as potential cluster stars. The initial stellar mass of t… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1201.5376v2-abstract-full').style.display = 'inline'; document.getElementById('1201.5376v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1201.5376v2-abstract-full" style="display: none;"> We present tentative evidence for the existence of a dissolved star cluster at [Fe/H]=-2.7 in the Sextans dwarf spheroidal galaxy. We use the technique of chemical tagging to identify stars that are highly clustered in a multi-dimensional chemical abundance space (C-space). In a sample of six stars, three, possibly four stars are identified as potential cluster stars. The initial stellar mass of the parent cluster is estimated from two independent observations to M*,init=1.9^{+1.5}_{-0.9} (1.6^{+1.2}_{-0.8}) x 10^5 M_sol, assuming a Salpeter (Kroupa) initial mass function (IMF). If corroborated by follow-up spectroscopy, this star cluster is the most metal-poor system identified to date. Chemical signatures of remnant clusters in dwarf galaxies like Sextans provide us with a very powerful probe to the high-redshift Universe. From available observational data, we argue that the average star cluster mass in the majority of the newly discovered ultra-faint dwarf galaxies was notably lower than it is in the Galaxy today and possibly lower than in the more luminous, classical dwarf spheroidal galaxies. Furthermore, the mean cumulative metallicity function of the dwarf spheroidals falls below that of the ultra-faints, which increases with increasing metallicity as predicted from our stochastic chemical evolution model. These two findings, together with a possible difference in the <[Mg/Fe]> ratio suggest that the ultra-faint dwarf galaxy population, or a significant fraction thereof, and the dwarf spheroidal population, were formed in different environments and would thus be distinct in origin. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1201.5376v2-abstract-full').style.display = 'none'; document.getElementById('1201.5376v2-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 August, 2012; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 January, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2012. </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, 8 figures, new Fig. 5, some clarifications, references added, accepted for publication in the ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1101.4024">arXiv:1101.4024</a> <span> [<a href="https://arxiv.org/pdf/1101.4024">pdf</a>, <a href="https://arxiv.org/ps/1101.4024">ps</a>, <a href="https://arxiv.org/format/1101.4024">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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/10.1103/RevModPhys.85.809">10.1103/RevModPhys.85.809 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Pre-galactic metal enrichment - The chemical signatures of the first stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">Torgny Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Bromm%2C+V">Volker Bromm</a>, <a href="/search/astro-ph?searchtype=author&query=Bland-Hawthorn%2C+J">Joss Bland-Hawthorn</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="1101.4024v2-abstract-short" style="display: inline;"> The emergence of the first sources of light at redshifts of z ~ 10-30 signaled the transition from the simple initial state of the Universe to one of increasing complexity. We review recent progress in our understanding of the formation of the first stars and galaxies, starting with cosmological initial conditions, primordial gas cooling, and subsequent collapse and fragmentation. We emphasize the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1101.4024v2-abstract-full').style.display = 'inline'; document.getElementById('1101.4024v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1101.4024v2-abstract-full" style="display: none;"> The emergence of the first sources of light at redshifts of z ~ 10-30 signaled the transition from the simple initial state of the Universe to one of increasing complexity. We review recent progress in our understanding of the formation of the first stars and galaxies, starting with cosmological initial conditions, primordial gas cooling, and subsequent collapse and fragmentation. We emphasize the important open question of how the pristine gas was enriched with heavy chemical elements in the wake of the first supernovae. We conclude by discussing how the chemical abundance patterns conceivably allow us to probe the properties of the first stars and subsequent stellar generations, and allow us to test models of early metal enrichment. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1101.4024v2-abstract-full').style.display = 'none'; document.getElementById('1101.4024v2-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> 6 September, 2012; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 20 January, 2011; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2011. </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">52 pages, 20 figures, clarifications, references added, accepted for publication in the Reviews of Modern Physics</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1007.5374">arXiv:1007.5374</a> <span> [<a href="https://arxiv.org/pdf/1007.5374">pdf</a>, <a href="https://arxiv.org/format/1007.5374">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</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/10.1088/0004-637X/721/1/582">10.1088/0004-637X/721/1/582 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Chemical signatures of the first star clusters </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Bland-Hawthorn%2C+J">Joss Bland-Hawthorn</a>, <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">Torgny Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Sharma%2C+S">Sanjib Sharma</a>, <a href="/search/astro-ph?searchtype=author&query=Krumholz%2C+M">Mark Krumholz</a>, <a href="/search/astro-ph?searchtype=author&query=Silk%2C+J">Joe Silk</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="1007.5374v1-abstract-short" style="display: inline;"> The chemical abundance patterns of the oldest stars in the Galaxy are expected to contain residual signatures of the first stars in the early universe. Numerous studies attempt to explain the intrinsic abundance scatter observed in some metal-poor populations in terms of chemical inhomogeneities dispersed throughout the early Galactic medium due to discrete enrichment events. Just how the complex… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1007.5374v1-abstract-full').style.display = 'inline'; document.getElementById('1007.5374v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1007.5374v1-abstract-full" style="display: none;"> The chemical abundance patterns of the oldest stars in the Galaxy are expected to contain residual signatures of the first stars in the early universe. Numerous studies attempt to explain the intrinsic abundance scatter observed in some metal-poor populations in terms of chemical inhomogeneities dispersed throughout the early Galactic medium due to discrete enrichment events. Just how the complex data and models are to be interpreted with respect to "progenitor yields" remains an open question. Here we show that stochastic chemical evolution models to date have overlooked a crucial fact. Essentially all stars today are born in highly homogeneous star clusters and it is likely that this was also true at early times. When this ingredient is included, the overall scatter in the abundance plane [Fe/H] vs. [X/Fe] (C-space), where X is a nucleosynthetic element, can be much less than derived from earlier models. Moreover, for moderately flat cluster mass functions (gamma < 2), and/or for mass functions with a high mass cut-off (M_max > 10^5 M_sun), stars exhibit a high degree of clumping in C-space that can be identified even in relatively small data samples. Since stellar abundances can be modified by mass transfer in close binaries, clustered signatures are essential for deriving the yields of the first supernovae. We present a statistical test to determine whether a given set of observations exhibit such behaviour. Our initial work focusses on two dimensions in C-space, but we show that the clustering signal can be greatly enhanced by additional abundance axes. The proposed experiment will be challenging on existing 8-10m telescopes, but relatively straightforward for a multi-object echelle spectrograph mounted on a 25-40m telescope. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1007.5374v1-abstract-full').style.display = 'none'; document.getElementById('1007.5374v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 30 July, 2010; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2010. </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">24 pages, 17 figs; Astrophysical Journal (Sept 20 issue); a full copy is available at http://sydney.edu.au/science/physics/~jbh/share/firststarclusters.pdf</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1006.3594">arXiv:1006.3594</a> <span> [<a href="https://arxiv.org/pdf/1006.3594">pdf</a>, <a href="https://arxiv.org/ps/1006.3594">ps</a>, <a href="https://arxiv.org/format/1006.3594">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/10.1051/0004-6361/201015226">10.1051/0004-6361/201015226 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Hamburg/ESO R-process Enhanced Star survey (HERES) VI. The Galactic Chemical Evolution of Silicon </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Zhang%2C+L">L. Zhang</a>, <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">T. Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Christlieb%2C+N">N. Christlieb</a>, <a href="/search/astro-ph?searchtype=author&query=Korn%2C+A+J">A. J. Korn</a>, <a href="/search/astro-ph?searchtype=author&query=Barklem%2C+P+S">P. S. Barklem</a>, <a href="/search/astro-ph?searchtype=author&query=Zhao%2C+G">G. Zhao</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="1006.3594v3-abstract-short" style="display: inline;"> We determined the silicon abundances of 253 metal-poor stars in the metallicity range $-4<\mathrm{[Fe/H]} <-1.5$, based on non-local thermodynamic equilibrium (NLTE) line formation calculations of neutral silicon and high-resolution spectra obtained with VLT-UT2/UVES. The $T_{\mathrm{eff}}$ dependence of [Si/Fe] noticed in previous investigation is diminished in our abundance analysis due to the i… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1006.3594v3-abstract-full').style.display = 'inline'; document.getElementById('1006.3594v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1006.3594v3-abstract-full" style="display: none;"> We determined the silicon abundances of 253 metal-poor stars in the metallicity range $-4<\mathrm{[Fe/H]} <-1.5$, based on non-local thermodynamic equilibrium (NLTE) line formation calculations of neutral silicon and high-resolution spectra obtained with VLT-UT2/UVES. The $T_{\mathrm{eff}}$ dependence of [Si/Fe] noticed in previous investigation is diminished in our abundance analysis due to the inclusion of NLTE effects. An increasing slope of [Si/Fe] towards decreasing metallicity is present in our results, in agreement with Galactic chemical evolution models. The small intrinsic scatter of [Si/Fe] in our sample may imply that these stars formed in a region where the yields of type II supernovae were mixed into a large volume, or that the formation of these stars was strongly clustered, even if the ISM was enriched by single SNa II in a small mixing volume. We identified two dwarfs with $\mathrm{[Si/Fe]}\sim +1.0$: HE 0131$-$3953, and HE 1430$-$1123. These main-sequence turnoff stars are also carbon-enhanced. They might have been pre-enriched by sub-luminous supernovae. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1006.3594v3-abstract-full').style.display = 'none'; document.getElementById('1006.3594v3-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 January, 2011; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 17 June, 2010; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2010. </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, 9 figures, 1 electronical table. Accepted by 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/0709.4025">arXiv:0709.4025</a> <span> [<a href="https://arxiv.org/pdf/0709.4025">pdf</a>, <a href="https://arxiv.org/ps/0709.4025">ps</a>, <a href="https://arxiv.org/format/0709.4025">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</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/10.1086/533520">10.1086/533520 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Uncovering the Chemical Signature of the First Stars in the Universe </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">Torgny Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Johnson%2C+J+L">Jarrett L. Johnson</a>, <a href="/search/astro-ph?searchtype=author&query=Bromm%2C+V">Volker Bromm</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="0709.4025v2-abstract-short" style="display: inline;"> The chemical abundance patterns observed in metal-poor Galactic halo stars contain the signature of the first supernovae, and thus allows us to probe the first stars that formed in the universe. We construct a theoretical model for the early chemical enrichment history of the Milky Way, aiming in particular at the contribution from pair-instability supernovae (PISNe). These are a natural consequ… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0709.4025v2-abstract-full').style.display = 'inline'; document.getElementById('0709.4025v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0709.4025v2-abstract-full" style="display: none;"> The chemical abundance patterns observed in metal-poor Galactic halo stars contain the signature of the first supernovae, and thus allows us to probe the first stars that formed in the universe. We construct a theoretical model for the early chemical enrichment history of the Milky Way, aiming in particular at the contribution from pair-instability supernovae (PISNe). These are a natural consequence of current theoretical models for primordial star formation at the highest masses. However, no metal-poor star displaying the distinct PISN signature has yet been observed. We here argue that this apparent absence of any PISN signature is due to an observational selection effect. Whereas most surveys traditionally focus on the most metal-poor stars, we predict that early PISN enrichment tends to `overshoot', reaching enrichment levels of [Ca/H] ~= -2.5 that would be missed by current searches. We utilize existing observational data to place constraints on the primordial initial mass function (IMF). The number fraction of PISNe in the primordial stellar population is estimated to be <0.07, or ~< 40% by mass, assuming that metal-free stars have masses in excess of 10 M_sun. We further predict, based on theoretical estimates for the relative number of PISNe, that the expected fraction of second generation stars below [Ca/H]=-2 with a dominant (i.e., >90%) contribution from PISNe is merely ~1e-4 - 5e-4. The corresponding fraction of stars formed from gas exclusively enriched by PISNe is a factor of ~4 smaller. With the advent of next generation telescopes and new, deeper surveys, we should be able to test these predictions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0709.4025v2-abstract-full').style.display = 'none'; document.getElementById('0709.4025v2-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 January, 2008; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 September, 2007; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2007. </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">17 pages, 6 figures, v2: mainly improvements on presentation, table added, references added, figure 6 modified, accepted for publication in ApJ</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> NORDITA-2007-029 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0602597">arXiv:astro-ph/0602597</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0602597">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0602597">ps</a>, <a href="https://arxiv.org/format/astro-ph/0602597">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</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/10.1086/503604">10.1086/503604 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Primordial Stellar Feedback and the Origin of Hyper Metal-Poor Stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">Torgny Karlsson</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="astro-ph/0602597v1-abstract-short" style="display: inline;"> The apparent absence of stars in the Milky Way halo with -5 ~< [Fe/H] ~< -4 suggests that the gas out of which the halo stars were born experienced a period of low or delayed star formation after the local universe was lit up by the first, metal-free generation of stars (Pop III). Negative feedback owed to the Pop III stars could initially have prevented the pre-Galactic halo from cooling, which… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0602597v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0602597v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0602597v1-abstract-full" style="display: none;"> The apparent absence of stars in the Milky Way halo with -5 ~< [Fe/H] ~< -4 suggests that the gas out of which the halo stars were born experienced a period of low or delayed star formation after the local universe was lit up by the first, metal-free generation of stars (Pop III). Negative feedback owed to the Pop III stars could initially have prevented the pre-Galactic halo from cooling, which thereby delayed the collapse and inhibited further star formation. During this period, however, the nucleosynthesis products of the first supernovae (SNe) had time to mix with the halo gas. As a result, the initially primordial gas was already weakly enriched in heavy elements, in particular iron, at the time of formation of the Galactic halo. The very high, observed C/Fe ratios in the two recently discovered hyper metal-poor stars ([Fe/H]<-5) HE 0107-5240 and HE 1327-2326 as well as the diversity of C/Fe ratios in the population of extremely metal-poor stars ([Fe/H]<-3) are then naturally explained by a combination of pre-enrichment by Pop III stars and local enrichment by subsequent generations of massive, rotating stars, for which the most massive ones end their lives as black hole-forming SNe, only ejecting their outer (carbon-rich) layers. The possible existence of populations of mega metal-poor/iron-free stars ([Fe/H]<-6) is also discussed. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0602597v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0602597v1-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> 27 February, 2006; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2006. </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, 3 figures, accepted for publication in ApJ Letters</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> NORDITA-2006-4 </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophys.J.641:L41-L44,2006 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0504617">arXiv:astro-ph/0504617</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0504617">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0504617">ps</a>, <a href="https://arxiv.org/format/astro-ph/0504617">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</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/10.1051/0004-6361:20042168">10.1051/0004-6361:20042168 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Stochastic chemical enrichment in metal-poor systems II. Abundance ratios and scatter </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">T. Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Gustafsson%2C+B">B. Gustafsson</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="astro-ph/0504617v1-abstract-short" style="display: inline;"> A stochastic model of the chemical enrichment of metal-poor systems by core-collapse supernovae is used to study the scatter in stellar abundance ratios. The resulting scatter in abundance ratios, e.g. as functions of the overall metallicity, is demonstrated to be crucially dependent on the as yet uncertain supernovae yields. The observed abundance ratios and their scatters therefore have diagno… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0504617v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0504617v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0504617v1-abstract-full" style="display: none;"> A stochastic model of the chemical enrichment of metal-poor systems by core-collapse supernovae is used to study the scatter in stellar abundance ratios. The resulting scatter in abundance ratios, e.g. as functions of the overall metallicity, is demonstrated to be crucially dependent on the as yet uncertain supernovae yields. The observed abundance ratios and their scatters therefore have diagnostic power as regards the yields. The relatively small star-to-star scatter observed in many chemical abundance ratios, e.g. by Cayrel et al. (2004) for stars down to [Fe/H] = -4, is tentatively explained by the averaging of a large number of contributing supernovae and by the cosmic selection effects favoring contributions from supernovae in a certain mass range for the most metal-poor stars. The scatter in observed abundances of alpha-elements is understood in terms of observational errors only, while additional spread in yields or sites of nucleosynthesis may affect the odd-even elements Na and Al. For the iron-group elements we find systematically too high predicted Cr/Fe and Cr/Mg ratios, as well as differences between the different sets of yields, both in terms of predicted abundance ratios and scatter. The semi-empirical yields recently suggested by Francois et al. (2004) are found to lead to scatter in abundance ratios significantly greater than observed, when applied in the inhomogeneous models. "Spurs", very narrow sequences in abundance-ratio diagrams, may disclose a single-supernova origin of the elements of the stars on the sequence. Verification of the existence of such features, called single supernova sequences (SSSs), is challenging. This will require samples of several hundred stars with abundance ratios observed to accuracies of 0.05 dex or better. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0504617v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0504617v1-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> 27 April, 2005; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2005. </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, 20 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/astro-ph/0504615">arXiv:astro-ph/0504615</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0504615">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0504615">ps</a>, <a href="https://arxiv.org/format/astro-ph/0504615">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</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/10.1051/0004-6361:20041934">10.1051/0004-6361:20041934 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Stochastic chemical enrichment in metal-poor systems I. Theory </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">T. Karlsson</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="astro-ph/0504615v1-abstract-short" style="display: inline;"> A stochastic model of the chemical enrichment of metal-poor systems by core-collapse (Type II) supernovae is presented, allowing for large-scale mixing of the enriched material by turbulent motions and cloud collisions in the interstellar medium. Infall of pristine material is taken into account by following the evolution of the gas density in the medium. Analytical expressions were derived for… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0504615v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0504615v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0504615v1-abstract-full" style="display: none;"> A stochastic model of the chemical enrichment of metal-poor systems by core-collapse (Type II) supernovae is presented, allowing for large-scale mixing of the enriched material by turbulent motions and cloud collisions in the interstellar medium. Infall of pristine material is taken into account by following the evolution of the gas density in the medium. Analytical expressions were derived for the number of stars enriched by a given number of supernovae, as well as for the amount of mass with which the ejected material from a supernova is mixed before being locked up in a subsequently formed star. It is shown that for reasonable values of the gas density (~0.1 cm-3) and of the supernova rate (~0.25 kpc-3 Myr-1) of the Galactic halo, the resulting metallicity distributions of the extreme Population II stars show a distinct cut-off at [Fe/H] ~= -4. In fact, by assuming no low-mass Population III stars were able to form out of the primordial interstellar medium, the derived fraction of stars below [Fe/H] = -4 is in agreement with observations. Moreover, the probability is high that even the most metal-poor stars observed to date have been enriched by several contributing supernovae. This partly explains the relatively small star-to-star scatter in many chemical-abundance ratios for stars down to [Fe/H] = -4, as recently found in several observational studies. Contribution from the thermonuclear (Type Ia) supernovae is found to be negligible over almost the entire extremely metal-poor regime. (***abridged***) <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0504615v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0504615v1-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> 27 April, 2005; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2005. </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, 10 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/astro-ph/0405286">arXiv:astro-ph/0405286</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0405286">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0405286">ps</a>, <a href="https://arxiv.org/format/astro-ph/0405286">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</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/10.1086/422576">10.1086/422576 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Abundances In Very Metal Poor Dwarf Stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Cohen%2C+J+G">Judith G. Cohen</a>, <a href="/search/astro-ph?searchtype=author&query=Christlieb%2C+N">Norbert Christlieb</a>, <a href="/search/astro-ph?searchtype=author&query=McWilliam%2C+A">Andrew McWilliam</a>, <a href="/search/astro-ph?searchtype=author&query=Shectman%2C+S">Steve Shectman</a>, <a href="/search/astro-ph?searchtype=author&query=Thompson%2C+I">Ian Thompson</a>, <a href="/search/astro-ph?searchtype=author&query=Wasserburg%2C+G+J">G. J. Wasserburg</a>, <a href="/search/astro-ph?searchtype=author&query=Ivans%2C+I">Inese Ivans</a>, <a href="/search/astro-ph?searchtype=author&query=Dehn%2C+M">Matthias Dehn</a>, <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">Torgny Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Melendez%2C+J">J. Melendez</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="astro-ph/0405286v1-abstract-short" style="display: inline;"> We discuss the detailed composition of 28 extremely metal-poor dwarfs, 22 of which are from the Hamburg/ESO Survey, based on Keck Echelle spectra. Our sample has a median [Fe/H] of -2.7 dex, extends to -3.5 dex, and is somewhat less metal-poor than was expected from [Fe/H](HK,HES) determined from low resolution spectra. Our analysis supports the existence of a sharp decline in the distribution o… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0405286v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0405286v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0405286v1-abstract-full" style="display: none;"> We discuss the detailed composition of 28 extremely metal-poor dwarfs, 22 of which are from the Hamburg/ESO Survey, based on Keck Echelle spectra. Our sample has a median [Fe/H] of -2.7 dex, extends to -3.5 dex, and is somewhat less metal-poor than was expected from [Fe/H](HK,HES) determined from low resolution spectra. Our analysis supports the existence of a sharp decline in the distribution of halo stars with metallicity below [Fe/H] = -3.0 dex. So far no additional turnoff stars with [Fe/H]}<-3.5 have been identified in our follow up efforts. For the best observed elements between Mg and Ni, we find that the abundance ratios appear to have reached a plateau, i.e. [X/Fe] is approximately constant as a function of [Fe/H], except for Cr, Mn and Co, which show trends of abundance ratios varying with [Fe/H]. These abundance ratios at low metallicity correspond approximately to the yield expected from Type II SN with a narrow range in mass and explosion parameters; high mass Type II SN progenitors are required. The dispersion of [X/Fe] about this plateau level is surprisingly small, and is still dominated by measurement errors rather than intrinsic scatter. The dispersion in neutron-capture elements, and the abundance trends for Cr, Mn and Co are consistent with previous studies of evolved EMP stars. Two dwarfs in the sample are carbon stars, while two others have significant C enhancements, all with C12/C13 ~ 7 and with C/N between 10 and 150. Three of these C-rich stars have large enhancements of the heavy neutron capture elements, including lead, which implies a strong s-process contribution, presumably from binary mass transfer; the fourth shows no excess of Sr or Ba. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0405286v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0405286v1-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 May, 2004; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2004. </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 ApJ</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophys.J. 612 (2004) 1107-1135 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0311173">arXiv:astro-ph/0311173</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0311173">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0311173">ps</a>, <a href="https://arxiv.org/format/astro-ph/0311173">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</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/10.1086/381237">10.1086/381237 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> HE0107-5240, A Chemically Ancient Star.I. A Detailed Abundance Analysis </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Christlieb%2C+N">N. Christlieb</a>, <a href="/search/astro-ph?searchtype=author&query=Gustafsson%2C+B">B. Gustafsson</a>, <a href="/search/astro-ph?searchtype=author&query=Korn%2C+A+J">A. J. Korn</a>, <a href="/search/astro-ph?searchtype=author&query=Barklem%2C+P+S">P. S. Barklem</a>, <a href="/search/astro-ph?searchtype=author&query=Beers%2C+T+C">T. C. Beers</a>, <a href="/search/astro-ph?searchtype=author&query=Bessell%2C+M+S">M. S. Bessell</a>, <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">T. Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Mizuno-Wiedner%2C+M">M. Mizuno-Wiedner</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="astro-ph/0311173v1-abstract-short" style="display: inline;"> We report a detailed abundance analysis for HE0107-5240, a halo giant with [Fe/H]_NLTE=-5.3. This star was discovered in the course of follow-up medium-resolution spectroscopy of extremely metal-poor candidates selected from the digitized Hamburg/ESO objective-prism survey. On the basis of high-resolution VLT/UVES spectra, we derive abundances for 8 elements (C, N, Na, Mg, Ca, Ti, Fe, and Ni), a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0311173v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0311173v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0311173v1-abstract-full" style="display: none;"> We report a detailed abundance analysis for HE0107-5240, a halo giant with [Fe/H]_NLTE=-5.3. This star was discovered in the course of follow-up medium-resolution spectroscopy of extremely metal-poor candidates selected from the digitized Hamburg/ESO objective-prism survey. On the basis of high-resolution VLT/UVES spectra, we derive abundances for 8 elements (C, N, Na, Mg, Ca, Ti, Fe, and Ni), and upper limits for another 12 elements. A plane-parallel LTE model atmosphere has been specifically tailored for the chemical composition of {\he}. Scenarios for the origin of the abundance pattern observed in the star are discussed. We argue that HE0107-5240 is most likely not a post-AGB star, and that the extremely low abundances of the iron-peak, and other elements, are not due to selective dust depletion. The abundance pattern of HE0107-5240 can be explained by pre-enrichment from a zero-metallicity type-II supernova of 20-25M_Sun, plus either self-enrichment with C and N, or production of these elements in the AGB phase of a formerly more massive companion, which is now a white dwarf. However, significant radial velocity variations have not been detected within the 52 days covered by our moderate-and high-resolution spectra. Alternatively, the abundance pattern can be explained by enrichment of the gas cloud from which HE0107-5240 formed by a 25M_Sun first-generation star exploding as a subluminous SNII, as proposed by Umeda & Nomoto (2003). We discuss consequences of the existence of HE0107-5240 for low-mass star formation in extremely metal-poor environments, and for currently ongoing and future searches for the most metal-poor stars in the Galaxy. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0311173v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0311173v1-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 November, 2003; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2003. </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">60 pages, 16 figures. Accepted for publication in ApJ</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophys.J.603:708-728,2004 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0211274">arXiv:astro-ph/0211274</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0211274">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0211274">ps</a>, <a href="https://arxiv.org/format/astro-ph/0211274">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</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/10.1038/nature01142">10.1038/nature01142 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A stellar relic from the early Milky Way </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Christlieb%2C+N">Norbert Christlieb</a>, <a href="/search/astro-ph?searchtype=author&query=Bessell%2C+M+S">Michael S. Bessell</a>, <a href="/search/astro-ph?searchtype=author&query=Beers%2C+T+C">Timothy C. Beers</a>, <a href="/search/astro-ph?searchtype=author&query=Gustafsson%2C+B">Bengt Gustafsson</a>, <a href="/search/astro-ph?searchtype=author&query=Korn%2C+A">Andreas Korn</a>, <a href="/search/astro-ph?searchtype=author&query=Barklem%2C+P+S">Paul S. Barklem</a>, <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">Torgny Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Mizuno-Wiedner%2C+M">Michelle Mizuno-Wiedner</a>, <a href="/search/astro-ph?searchtype=author&query=Rossi%2C+S">Silvia Rossi</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="astro-ph/0211274v1-abstract-short" style="display: inline;"> The chemical composition of the most metal-deficient stars reflects the composition of the gas from which they formed. These old stars provide crucial clues to the star formation history and the synthesis of chemical elements in the early Universe. They are the local relics of epochs otherwise observable only at very high redshifts; if totally metal-free (``population III'') stars could be found… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0211274v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0211274v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0211274v1-abstract-full" style="display: none;"> The chemical composition of the most metal-deficient stars reflects the composition of the gas from which they formed. These old stars provide crucial clues to the star formation history and the synthesis of chemical elements in the early Universe. They are the local relics of epochs otherwise observable only at very high redshifts; if totally metal-free (``population III'') stars could be found, this would allow the direct study of the pristine gas from the Big Bang. Earlier searches for such stars found none with an iron abundance less than 1/10,000 that of the Sun, leading to the suggestion that low-mass stars could only form from clouds above a critical iron abundance. Here we report the discovery of a low-mass star with an iron abundance as low as 1/200,000 of the solar value. This discovery suggests that population III stars could still exist, that is, that the first generation of stars also contained long-lived low-mass objects. The previous failure to find them may be an observational selection effect. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0211274v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0211274v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 November, 2002; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2002. </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">Offprint of Nature 419 (2002), 904-906 (issue 31 October 2002)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature 419 (2002) 904-906 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0109010">arXiv:astro-ph/0109010</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0109010">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0109010">ps</a>, <a href="https://arxiv.org/format/astro-ph/0109010">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</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/10.1051/0004-6361:20011217">10.1051/0004-6361:20011217 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Chemical abundance patterns -- fingerprints of nucleosynthesis in the first stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">T. Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Gustafsson%2C+B">B. Gustafsson</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="astro-ph/0109010v2-abstract-short" style="display: inline;"> The interstellar medium of low-metallicity systems undergoing star formation will show chemical abundance inhomogeneities due to supernova events enriching the medium on a local scale. If the star formation time-scale is shorter than the time-scale of mixing of the interstellar matter, the inhomogeneities are reflected in the surface abundances of low-mass stars and thereby detailed information… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0109010v2-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0109010v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0109010v2-abstract-full" style="display: none;"> The interstellar medium of low-metallicity systems undergoing star formation will show chemical abundance inhomogeneities due to supernova events enriching the medium on a local scale. If the star formation time-scale is shorter than the time-scale of mixing of the interstellar matter, the inhomogeneities are reflected in the surface abundances of low-mass stars and thereby detailed information on the nucleosynthesis in the first generations of supernovae is preserved. Characteristic patterns and substructures are therefore expected to be found, apart from the large scatter behaviour, in the distributions of stars when displayed in diagrams relating different element abundance ratios. These patterns emerge from specific variations with progenitor stellar mass of the supernova yields and it is demonstrated that the patterns are insensitive to the initial mass function (IMF) even though the relative density of stars within the patterns may vary. An analytical theory of the formation of patterns is presented and it is shown that from a statistical point of view the abundance ratios can trace the different nucleosynthesis sites even when mixing of the interstellar medium occurs. Using these results, it should be possible to empirically determine supernova yields from the information on relative abundance ratios of a large, homogeneous sample of extremely metal-poor Galactic halo stars. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0109010v2-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0109010v2-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 July, 2002; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 2 September, 2001; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2001. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">20 pages, minor typos corrected to match the published version in A&A. Includes the corrected Figs. 17 and 18 (erratum)</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/9811303">arXiv:astro-ph/9811303</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/9811303">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/9811303">ps</a>, <a href="https://arxiv.org/format/astro-ph/9811303">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> </div> <p class="title is-5 mathjax"> The origin of carbon, investigated by spectral analysis of solar-type stars in the Galactic Disk </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Gustafsson%2C+B">B. Gustafsson</a>, <a href="/search/astro-ph?searchtype=author&query=Karlsson%2C+T">T. Karlsson</a>, <a href="/search/astro-ph?searchtype=author&query=Olsson%2C+E">E. Olsson</a>, <a href="/search/astro-ph?searchtype=author&query=Edvardsson%2C+B">B. Edvardsson</a>, <a href="/search/astro-ph?searchtype=author&query=Ryde%2C+N">N. Ryde</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="astro-ph/9811303v1-abstract-short" style="display: inline;"> Abundance analysis of carbon has been performed in a sample of 80 late F and early G type dwarf stars in the metallicity range -1.06 < [Fe/H] < 0.26 using the forbidden [C I] line at 8727 A. This line is presumably less sensitive to temperature, atmospheric structure and departures from LTE than alternative carbon criteria. We find that [C/Fe] decreases slowly with increasing [Fe/H] with an over… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/9811303v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/9811303v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/9811303v1-abstract-full" style="display: none;"> Abundance analysis of carbon has been performed in a sample of 80 late F and early G type dwarf stars in the metallicity range -1.06 < [Fe/H] < 0.26 using the forbidden [C I] line at 8727 A. This line is presumably less sensitive to temperature, atmospheric structure and departures from LTE than alternative carbon criteria. We find that [C/Fe] decreases slowly with increasing [Fe/H] with an overall slope of -0.17 +- 0.03. Our results are consistent with carbon enrichment by superwinds of metal-rich massive stars but inconsistent with a main origin of carbon in low-mass stars. This follows in particular from a comparison between the relation of [C/O] with metallicity for the Galactic stars and the corresponding relation observed for dwarf irregular galaxies. The significance of intermediate-mass stars for the production of carbon in the Galaxy is still somewhat unclear. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/9811303v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/9811303v1-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 November, 1998; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 1998. </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 including 10 Postscript figures, Uses l-aa.sty, Accepted for publication in Astronomy & Astrophysics, Complete Postscript file available at ftp://ftp.astro.uu.se/pub/articles/atmos/P133</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> UAO-98-P133 </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astron.Astrophys.342:426,1999 </p> </li> </ol> <div class="is-hidden-tablet">  <span class="help" style="display: inline-block;"><a href="https://github.com/arXiv/arxiv-search/releases">Search v0.5.6 released 2020-02-24</a>  </span> </div> </div> </main> <footer> <div class="columns is-desktop" role="navigation" aria-label="Secondary">  <div class="column"> <div class="columns"> <div class="column"> <ul class="nav-spaced"> <li><a href="https://info.arxiv.org/about">About</a></li> <li><a href="https://info.arxiv.org/help">Help</a></li> </ul> </div> <div class="column"> <ul class="nav-spaced"> <li> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" class="icon filter-black" role="presentation"><title>contact arXiv</title><desc>Click here to contact arXiv</desc><path d="M502.3 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