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<button class="button is-small is-link">Go</button> </div> </div> </form> </div> </div> <nav class="pagination is-small is-centered breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" class="pagination-previous is-invisible">Previous </a> <a href="/search/?searchtype=author&query=Brown%2C+E+F&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Brown%2C+E+F&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Brown%2C+E+F&start=50" class="pagination-link " aria-label="Page 2" aria-current="page">2 </a> </li> </ul> </nav> <ol class="breathe-horizontal" start="1"> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2306.12451">arXiv:2306.12451</a> <span> [<a href="https://arxiv.org/pdf/2306.12451">pdf</a>, <a href="https://arxiv.org/format/2306.12451">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Nuclear Theory">nucl-th</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/acebc4">10.3847/1538-4357/acebc4 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Impact of Pycnonuclear Fusion Uncertainties on the Cooling of Accreting Neutron Star Crusts </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Jain%2C+R">R. Jain</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Schatz%2C+H">H. Schatz</a>, <a href="/search/astro-ph?searchtype=author&query=Afanasjev%2C+A+V">A. V. Afanasjev</a>, <a href="/search/astro-ph?searchtype=author&query=Beard%2C+M">M. Beard</a>, <a href="/search/astro-ph?searchtype=author&query=Gasques%2C+L+R">L. R. Gasques</a>, <a href="/search/astro-ph?searchtype=author&query=Gupta%2C+S+S">S. S. Gupta</a>, <a href="/search/astro-ph?searchtype=author&query=Hitt%2C+G+W">G. W. Hitt</a>, <a href="/search/astro-ph?searchtype=author&query=Hix%2C+W+R">W. R. Hix</a>, <a href="/search/astro-ph?searchtype=author&query=Lau%2C+R">R. Lau</a>, <a href="/search/astro-ph?searchtype=author&query=Moller%2C+P">P. Moller</a>, <a href="/search/astro-ph?searchtype=author&query=Ong%2C+W+J">W. J. Ong</a>, <a href="/search/astro-ph?searchtype=author&query=Wiescher%2C+M">M. Wiescher</a>, <a href="/search/astro-ph?searchtype=author&query=Xu%2C+Y">Y. Xu</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2306.12451v2-abstract-short" style="display: inline;"> The observation of X-rays during quiescence from transiently accreting neutron stars provides unique clues about the nature of dense matter. This, however, requires extensive modeling of the crusts and matching the results to observations. The pycnonuclear fusion reaction rates implemented in these models are theoretically calculated by extending phenomenological expressions and have large uncerta… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.12451v2-abstract-full').style.display = 'inline'; document.getElementById('2306.12451v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2306.12451v2-abstract-full" style="display: none;"> The observation of X-rays during quiescence from transiently accreting neutron stars provides unique clues about the nature of dense matter. This, however, requires extensive modeling of the crusts and matching the results to observations. The pycnonuclear fusion reaction rates implemented in these models are theoretically calculated by extending phenomenological expressions and have large uncertainties spanning many orders of magnitude. We present the first sensitivity studies of these pycnonuclear fusion reactions in realistic network calculations. We also couple the reaction network with the thermal evolution code dStar to further study their impact on the neutron star cooling curves in quiescence. Varying the pycnonuclear fusion reaction rates alters the depth at which nuclear heat is deposited although the total heating remains constant. The enhancement of the pycnonuclear fusion reaction rates leads to an overall shallower deposition of nuclear heat. The impurity factors are also altered depending on the type of ashes deposited on the crust. These total changes correspond to a variation of up to 9 eV in the modeled cooling curves. While this is not sufficient to explain the shallow heat source, it is comparable to the observational uncertainties and can still be important for modeling the neutron star crust. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.12451v2-abstract-full').style.display = 'none'; document.getElementById('2306.12451v2-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 October, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 20 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">AASTeX63, 11 pages with 9 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> ApJ 955 51 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2205.07996">arXiv:2205.07996</a> <span> [<a href="https://arxiv.org/pdf/2205.07996">pdf</a>, <a href="https://arxiv.org/format/2205.07996">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Nuclear Experiment">nucl-ex</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> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Nuclear Theory">nucl-th</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/10.1088/1361-6471/ac8890">10.1088/1361-6471/ac8890 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Horizons: Nuclear Astrophysics in the 2020s and Beyond </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Schatz%2C+H">H. Schatz</a>, <a href="/search/astro-ph?searchtype=author&query=Reyes%2C+A+D+B">A. D. Becerril Reyes</a>, <a href="/search/astro-ph?searchtype=author&query=Best%2C+A">A. Best</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Chatziioannou%2C+K">K. Chatziioannou</a>, <a href="/search/astro-ph?searchtype=author&query=Chipps%2C+K+A">K. A. Chipps</a>, <a href="/search/astro-ph?searchtype=author&query=Deibel%2C+C+M">C. M. Deibel</a>, <a href="/search/astro-ph?searchtype=author&query=Ezzeddine%2C+R">R. Ezzeddine</a>, <a href="/search/astro-ph?searchtype=author&query=Galloway%2C+D+K">D. K. Galloway</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+C+J">C. J. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Herwig%2C+F">F. Herwig</a>, <a href="/search/astro-ph?searchtype=author&query=Ji%2C+A+P">A. P. Ji</a>, <a href="/search/astro-ph?searchtype=author&query=Lugaro%2C+M">M. Lugaro</a>, <a href="/search/astro-ph?searchtype=author&query=Meisel%2C+Z">Z. Meisel</a>, <a href="/search/astro-ph?searchtype=author&query=Norman%2C+D">D. Norman</a>, <a href="/search/astro-ph?searchtype=author&query=Read%2C+J+S">J. S. Read</a>, <a href="/search/astro-ph?searchtype=author&query=Roberts%2C+L+F">L. F. Roberts</a>, <a href="/search/astro-ph?searchtype=author&query=Spyrou%2C+A">A. Spyrou</a>, <a href="/search/astro-ph?searchtype=author&query=Tews%2C+I">I. Tews</a>, <a href="/search/astro-ph?searchtype=author&query=Timmes%2C+F+X">F. X. Timmes</a>, <a href="/search/astro-ph?searchtype=author&query=Travaglio%2C+C">C. Travaglio</a>, <a href="/search/astro-ph?searchtype=author&query=Vassh%2C+N">N. Vassh</a>, <a href="/search/astro-ph?searchtype=author&query=Abia%2C+C">C. Abia</a>, <a href="/search/astro-ph?searchtype=author&query=Adsley%2C+P">P. Adsley</a>, <a href="/search/astro-ph?searchtype=author&query=Agarwal%2C+S">S. Agarwal</a> , et al. (140 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="2205.07996v1-abstract-short" style="display: inline;"> Nuclear Astrophysics is a field at the intersection of nuclear physics and astrophysics, which seeks to understand the nuclear engines of astronomical objects and the origin of the chemical elements. This white paper summarizes progress and status of the field, the new open questions that have emerged, and the tremendous scientific opportunities that have opened up with major advances in capabilit… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.07996v1-abstract-full').style.display = 'inline'; document.getElementById('2205.07996v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2205.07996v1-abstract-full" style="display: none;"> Nuclear Astrophysics is a field at the intersection of nuclear physics and astrophysics, which seeks to understand the nuclear engines of astronomical objects and the origin of the chemical elements. This white paper summarizes progress and status of the field, the new open questions that have emerged, and the tremendous scientific opportunities that have opened up with major advances in capabilities across an ever growing number of disciplines and subfields that need to be integrated. We take a holistic view of the field discussing the unique challenges and opportunities in nuclear astrophysics in regards to science, diversity, education, and the interdisciplinarity and breadth of the field. Clearly nuclear astrophysics is a dynamic field with a bright future that is entering a new era of discovery opportunities. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.07996v1-abstract-full').style.display = 'none'; document.getElementById('2205.07996v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 May, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">96 pages. Submitted to Journal of Physics G</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> LA-UR-22-23997 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2112.11544">arXiv:2112.11544</a> <span> [<a href="https://arxiv.org/pdf/2112.11544">pdf</a>, <a href="https://arxiv.org/format/2112.11544">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="Nuclear Theory">nucl-th</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/ac4271">10.3847/1538-4357/ac4271 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Impact of Neutron Transfer Reactions on Heating and Cooling of Accreted Neutron Star Crusts </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Schatz%2C+H">H. Schatz</a>, <a href="/search/astro-ph?searchtype=author&query=Meisel%2C+Z">Z. Meisel</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Gupta%2C+S+S">S. S. Gupta</a>, <a href="/search/astro-ph?searchtype=author&query=Hitt%2C+G+W">G. W. Hitt</a>, <a href="/search/astro-ph?searchtype=author&query=Hix%2C+W+R">W. R. Hix</a>, <a href="/search/astro-ph?searchtype=author&query=Jain%2C+R">R. Jain</a>, <a href="/search/astro-ph?searchtype=author&query=Lau%2C+R">R. Lau</a>, <a href="/search/astro-ph?searchtype=author&query=M%C3%B6ller%2C+P">P. M枚ller</a>, <a href="/search/astro-ph?searchtype=author&query=Ong%2C+W+-">W. -J. Ong</a>, <a href="/search/astro-ph?searchtype=author&query=Shternin%2C+P+S">P. S. Shternin</a>, <a href="/search/astro-ph?searchtype=author&query=Xu%2C+Y">Y. Xu</a>, <a href="/search/astro-ph?searchtype=author&query=Wiescher%2C+M">M. Wiescher</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="2112.11544v1-abstract-short" style="display: inline;"> Nuclear reactions heat and cool the crust of accreting neutron stars and need to be understood to interpret observations of X-ray bursts and of long-term cooling in transiently accreting systems. It was recently suggested that previously neglected neutron transfer reactions may play a significant role in the nuclear processes. We present results from full nuclear network calculations that now incl… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.11544v1-abstract-full').style.display = 'inline'; document.getElementById('2112.11544v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2112.11544v1-abstract-full" style="display: none;"> Nuclear reactions heat and cool the crust of accreting neutron stars and need to be understood to interpret observations of X-ray bursts and of long-term cooling in transiently accreting systems. It was recently suggested that previously neglected neutron transfer reactions may play a significant role in the nuclear processes. We present results from full nuclear network calculations that now include these reactions and determine their impact on crust composition, crust impurity, heating, and cooling. We find that a large number of neutron transfer reactions indeed occur and impact crust models. In particular, we identify a new type of reaction cycle that brings a pair of nuclei across the nuclear chart into equilibrium via alternating neutron capture and neutron release, interspersed with a neutron transfer. While neutron transfer reactions lead to changes in crust model predictions, and need to be considered in future studies, previous conclusions concerning heating, cooling, and compositional evolution are remarkably robust. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.11544v1-abstract-full').style.display = 'none'; document.getElementById('2112.11544v1-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 December, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 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">8 pages, 10 figures, accepted for Astrophysical 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/1906.01535">arXiv:1906.01535</a> <span> [<a href="https://arxiv.org/pdf/1906.01535">pdf</a>, <a href="https://arxiv.org/format/1906.01535">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/ab338c">10.3847/1538-4357/ab338c <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Crust Cooling Models are Insensitive to the Crust-Core Transition Pressure for Realistic Equations of State </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Lalit%2C+S">Sudhanva Lalit</a>, <a href="/search/astro-ph?searchtype=author&query=Meisel%2C+Z">Zach Meisel</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</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="1906.01535v1-abstract-short" style="display: inline;"> Neutron stars cooling after sustained accretion outbursts provide unique information about the neutron star crust and underlying dense matter. Comparisons between astronomical observations of these cooling transients and model calculations of neutron star crust cooling have frequently been used to constrain neutron star properties such as the mass, radius, crust composition, and presence of nuclea… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1906.01535v1-abstract-full').style.display = 'inline'; document.getElementById('1906.01535v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1906.01535v1-abstract-full" style="display: none;"> Neutron stars cooling after sustained accretion outbursts provide unique information about the neutron star crust and underlying dense matter. Comparisons between astronomical observations of these cooling transients and model calculations of neutron star crust cooling have frequently been used to constrain neutron star properties such as the mass, radius, crust composition, and presence of nuclear pasta. These calculations often use a fixed pressure at which the crust-core transition happens, though this quantity depends on the dense matter equation of state. We demonstrate that varying the crust-core transition pressure in a manner consistent with adopting various equations of state results in modest changes to the crust cooling light curve. This validates the approach adopted in most crust cooling studies to date, where the neutron star mass and radius are varied while leaving the crust-core transition pressure constant. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1906.01535v1-abstract-full').style.display = 'none'; document.getElementById('1906.01535v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 4 June, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 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">6 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1812.04023">arXiv:1812.04023</a> <span> [<a href="https://arxiv.org/pdf/1812.04023">pdf</a>, <a href="https://arxiv.org/format/1812.04023">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/s11433-017-9186-1">10.1007/s11433-017-9186-1 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Observatory science with eXTP </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Zand%2C+J+J+M+i+%27">Jean J. M. in 't Zand</a>, <a href="/search/astro-ph?searchtype=author&query=Bozzo%2C+E">Enrico Bozzo</a>, <a href="/search/astro-ph?searchtype=author&query=Qu%2C+J">Jinlu Qu</a>, <a href="/search/astro-ph?searchtype=author&query=Li%2C+X">Xiang-Dong Li</a>, <a href="/search/astro-ph?searchtype=author&query=Amati%2C+L">Lorenzo Amati</a>, <a href="/search/astro-ph?searchtype=author&query=Chen%2C+Y">Yang Chen</a>, <a href="/search/astro-ph?searchtype=author&query=Donnarumma%2C+I">Immacolata Donnarumma</a>, <a href="/search/astro-ph?searchtype=author&query=Doroshenko%2C+V">Victor Doroshenko</a>, <a href="/search/astro-ph?searchtype=author&query=Drake%2C+S+A">Stephen A. Drake</a>, <a href="/search/astro-ph?searchtype=author&query=Hernanz%2C+M">Margarita Hernanz</a>, <a href="/search/astro-ph?searchtype=author&query=Jenke%2C+P+A">Peter A. Jenke</a>, <a href="/search/astro-ph?searchtype=author&query=Maccarone%2C+T+J">Thomas J. Maccarone</a>, <a href="/search/astro-ph?searchtype=author&query=Mahmoodifar%2C+S">Simin Mahmoodifar</a>, <a href="/search/astro-ph?searchtype=author&query=de+Martino%2C+D">Domitilla de Martino</a>, <a href="/search/astro-ph?searchtype=author&query=De+Rosa%2C+A">Alessandra De Rosa</a>, <a href="/search/astro-ph?searchtype=author&query=Rossi%2C+E+M">Elena M. Rossi</a>, <a href="/search/astro-ph?searchtype=author&query=Rowlinson%2C+A">Antonia Rowlinson</a>, <a href="/search/astro-ph?searchtype=author&query=Sala%2C+G">Gloria Sala</a>, <a href="/search/astro-ph?searchtype=author&query=Stratta%2C+G">Giulia Stratta</a>, <a href="/search/astro-ph?searchtype=author&query=Tauris%2C+T+M">Thomas M. Tauris</a>, <a href="/search/astro-ph?searchtype=author&query=Wilms%2C+J">Joern Wilms</a>, <a href="/search/astro-ph?searchtype=author&query=Wu%2C+X">Xuefeng Wu</a>, <a href="/search/astro-ph?searchtype=author&query=Zhou%2C+P">Ping Zhou</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Iv谩n Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Altamirano%2C+D">Diego Altamirano</a> , et al. (159 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="1812.04023v1-abstract-short" style="display: inline;"> In this White Paper we present the potential of the enhanced X-ray Timing and Polarimetry (eXTP) mission for studies related to Observatory Science targets. These include flaring stars, supernova remnants, accreting white dwarfs, low and high mass X-ray binaries, radio quiet and radio loud active galactic nuclei, tidal disruption events, and gamma-ray bursts. eXTP will be excellently suited to stu… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1812.04023v1-abstract-full').style.display = 'inline'; document.getElementById('1812.04023v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1812.04023v1-abstract-full" style="display: none;"> In this White Paper we present the potential of the enhanced X-ray Timing and Polarimetry (eXTP) mission for studies related to Observatory Science targets. These include flaring stars, supernova remnants, accreting white dwarfs, low and high mass X-ray binaries, radio quiet and radio loud active galactic nuclei, tidal disruption events, and gamma-ray bursts. eXTP will be excellently suited to study one common aspect of these objects: their often transient nature. Developed by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Science, the eXTP mission is expected to be launched in the mid 2020s. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1812.04023v1-abstract-full').style.display = 'none'; document.getElementById('1812.04023v1-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, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication on Sci. China Phys. Mech. Astron. (2019)</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1810.05626">arXiv:1810.05626</a> <span> [<a href="https://arxiv.org/pdf/1810.05626">pdf</a>, <a href="https://arxiv.org/format/1810.05626">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/10.1051/0004-6361/201834412">10.1051/0004-6361/201834412 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Consistent accretion-induced heating of the neutron-star crust in MXB 1659-29 during two different outbursts </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Parikh%2C+A+S">A. S. Parikh</a>, <a href="/search/astro-ph?searchtype=author&query=Wijnands%2C+R">R. Wijnands</a>, <a href="/search/astro-ph?searchtype=author&query=Ootes%2C+L+S">L. S. Ootes</a>, <a href="/search/astro-ph?searchtype=author&query=Page%2C+D">D. Page</a>, <a href="/search/astro-ph?searchtype=author&query=Degenaar%2C+N">N. Degenaar</a>, <a href="/search/astro-ph?searchtype=author&query=Bahramian%2C+A">A. Bahramian</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Cackett%2C+E+M">E. M. Cackett</a>, <a href="/search/astro-ph?searchtype=author&query=Cumming%2C+A">A. Cumming</a>, <a href="/search/astro-ph?searchtype=author&query=Heinke%2C+C">C. Heinke</a>, <a href="/search/astro-ph?searchtype=author&query=Homan%2C+J">J. Homan</a>, <a href="/search/astro-ph?searchtype=author&query=Escorial%2C+A+R">A. Rouco Escorial</a>, <a href="/search/astro-ph?searchtype=author&query=Wijngaarden%2C+M+J+P">M. J. P. Wijngaarden</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="1810.05626v1-abstract-short" style="display: inline;"> Monitoring the cooling of neutron-star crusts heated during accretion outbursts allows us to infer the physics of the dense matter present in the crust. We examine the crust cooling evolution of the low-mass X-ray binary MXB 1659-29 up to ~505 days after the end of its 2015 outburst (hereafter outburst II) and compare it with what we observed after its previous 1999 outburst (hereafter outburst I)… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1810.05626v1-abstract-full').style.display = 'inline'; document.getElementById('1810.05626v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1810.05626v1-abstract-full" style="display: none;"> Monitoring the cooling of neutron-star crusts heated during accretion outbursts allows us to infer the physics of the dense matter present in the crust. We examine the crust cooling evolution of the low-mass X-ray binary MXB 1659-29 up to ~505 days after the end of its 2015 outburst (hereafter outburst II) and compare it with what we observed after its previous 1999 outburst (hereafter outburst I) using data obtained from the Swift, XMM-Newton, and Chandra observatories. The observed effective surface temperature of the neutron star in MXB 1659-29 dropped from ~92 eV to ~56 eV from ~12 days to ~505 days after the end of outburst II. The most recently performed observation after outburst II suggests that the crust is close to returning to thermal equilibrium with the core. We model the crust heating and cooling for both its outbursts collectively to understand the effect of parameters that may change for every outburst (e.g., the average accretion rate, the length of outburst, the envelope composition of the neutron star at the end of the outburst) and those which can be assumed to remain the same during these two outbursts (e.g., the neutron star mass, its radius). Our modelling indicates that all parameters were consistent between the two outbursts with no need for any significant changes. In particular, the strength and the depth of the shallow heating mechanism at work (in the crust) were inferred to be the same during both outbursts, contrary to what has been found when modelling the cooling curves after multiple outburst of another source, MAXI J0556-332. This difference in source behaviour is not understood. We discuss our results in the context of our current understanding of cooling of accretion-heated neutron-star crusts, and in particular with respect to the unexplained shallow heating mechanism. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1810.05626v1-abstract-full').style.display = 'none'; document.getElementById('1810.05626v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 October, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Submitted to A&A. The supplementary video can be found at https://www.youtube.com/watch?v=OpJ053zq9-M</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 624, A84 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1803.03818">arXiv:1803.03818</a> <span> [<a href="https://arxiv.org/pdf/1803.03818">pdf</a>, <a href="https://arxiv.org/format/1803.03818">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Nuclear Theory">nucl-th</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/aabfe0">10.3847/1538-4357/aabfe0 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Nuclear Reactions in the Crusts of Accreting Neutron Stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Lau%2C+R">R. Lau</a>, <a href="/search/astro-ph?searchtype=author&query=Beard%2C+M">M. Beard</a>, <a href="/search/astro-ph?searchtype=author&query=Gupta%2C+S+S">S. S. Gupta</a>, <a href="/search/astro-ph?searchtype=author&query=Schatz%2C+H">H. Schatz</a>, <a href="/search/astro-ph?searchtype=author&query=Afanasjev%2C+A+V">A. V. Afanasjev</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Deibel%2C+A">A. Deibel</a>, <a href="/search/astro-ph?searchtype=author&query=Gasques%2C+L+R">L. R. Gasques</a>, <a href="/search/astro-ph?searchtype=author&query=Hitt%2C+G+W">G. W. Hitt</a>, <a href="/search/astro-ph?searchtype=author&query=Hix%2C+W+R">W. R. Hix</a>, <a href="/search/astro-ph?searchtype=author&query=Keek%2C+L">L. Keek</a>, <a href="/search/astro-ph?searchtype=author&query=M%C3%B6ller%2C+P">P. M枚ller</a>, <a href="/search/astro-ph?searchtype=author&query=Shternin%2C+P+S">P. S. Shternin</a>, <a href="/search/astro-ph?searchtype=author&query=Steiner%2C+A">A. Steiner</a>, <a href="/search/astro-ph?searchtype=author&query=Wiescher%2C+M">M. Wiescher</a>, <a href="/search/astro-ph?searchtype=author&query=Xu%2C+Y">Y. Xu</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="1803.03818v2-abstract-short" style="display: inline;"> X-ray observations of transiently accreting neutron stars during quiescence provide information about the structure of neutron star crusts and the properties of dense matter. Interpretation of the observational data requires an understanding of the nuclear reactions that heat and cool the crust during accretion, and define its nonequilibrium composition. We identify here in detail the typical nucl… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1803.03818v2-abstract-full').style.display = 'inline'; document.getElementById('1803.03818v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1803.03818v2-abstract-full" style="display: none;"> X-ray observations of transiently accreting neutron stars during quiescence provide information about the structure of neutron star crusts and the properties of dense matter. Interpretation of the observational data requires an understanding of the nuclear reactions that heat and cool the crust during accretion, and define its nonequilibrium composition. We identify here in detail the typical nuclear reaction sequences down to a depth in the inner crust where the mass density is 2E12 g/cm^3 using a full nuclear reaction network for a range of initial compositions. The reaction sequences differ substantially from previous work. We find a robust reduction of crust impurity at the transition to the inner crust regardless of initial composition, though shell effects can delay the formation of a pure crust somewhat to densities beyond 2E12 g/cm^3. This naturally explains the small inner crust impurity inferred from observations of a broad range of systems. The exception are initial compositions with A >= 102 nuclei, where the inner crust remains impure with an impurity parameter of Qimp~20 due to the N = 82 shell closure. In agreement with previous work we find that nuclear heating is relatively robust and independent of initial composition, while cooling via nuclear Urca cycles in the outer crust depends strongly on initial composition. This work forms a basis for future studies of the sensitivity of crust models to nuclear physics and provides profiles of composition for realistic crust models. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1803.03818v2-abstract-full').style.display = 'none'; document.getElementById('1803.03818v2-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 April, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 10 March, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">25 Pages, accepted for publication in Ap. J</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1801.00041">arXiv:1801.00041</a> <span> [<a href="https://arxiv.org/pdf/1801.00041">pdf</a>, <a href="https://arxiv.org/format/1801.00041">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/PhysRevLett.120.182701">10.1103/PhysRevLett.120.182701 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Rapid neutrino cooling in the neutron star MXB 1659-29 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Cumming%2C+A">Andrew Cumming</a>, <a href="/search/astro-ph?searchtype=author&query=Fattoyev%2C+F+J">Farrukh J. Fattoyev</a>, <a href="/search/astro-ph?searchtype=author&query=Horowitz%2C+C+J">C. J. Horowitz</a>, <a href="/search/astro-ph?searchtype=author&query=Page%2C+D">Dany Page</a>, <a href="/search/astro-ph?searchtype=author&query=Reddy%2C+S">Sanjay Reddy</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="1801.00041v1-abstract-short" style="display: inline;"> We show that the neutron star in the transient system MXB~1659-29 has a core neutrino luminosity that substantially exceeds that of the modified Urca reactions (i.e., $n+n\to n+p+e^{-}+\bar谓_{e}$ and inverse) and is consistent with the direct Urca reactions ($n\to p+e^{-}+\bar谓_{e}$ and inverse) occurring in a small fraction of the core. Observations of the thermal relaxation of the neutron star c… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1801.00041v1-abstract-full').style.display = 'inline'; document.getElementById('1801.00041v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1801.00041v1-abstract-full" style="display: none;"> We show that the neutron star in the transient system MXB~1659-29 has a core neutrino luminosity that substantially exceeds that of the modified Urca reactions (i.e., $n+n\to n+p+e^{-}+\bar谓_{e}$ and inverse) and is consistent with the direct Urca reactions ($n\to p+e^{-}+\bar谓_{e}$ and inverse) occurring in a small fraction of the core. Observations of the thermal relaxation of the neutron star crust following 2.5 years of accretion allow us to measure the energy deposited into the core during accretion, which is then reradiated as neutrinos, and infer the core temperature. For a nucleonic core, this requires that the nucleons are unpaired and that the proton fraction exceed a critical value to allow the direct Urca reaction to proceed. The neutron star in MXB~1659-29 is the first with a firmly detected thermal component in its X-ray spectrum that needs a fast neutrino cooling process. Measurements of the temperature variation of the neutron star core during quiescence would place an upper limit on the core specific heat and serve as a check on the fraction of the neutron star core in which nucleons are unpaired. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1801.00041v1-abstract-full').style.display = 'none'; document.getElementById('1801.00041v1-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 December, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">5 pages, 3 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> INT-PUB-17-024 </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Lett. 120, 182701 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1710.10367">arXiv:1710.10367</a> <span> [<a href="https://arxiv.org/pdf/1710.10367">pdf</a>, <a href="https://arxiv.org/format/1710.10367">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="Nuclear Experiment">nucl-ex</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Nuclear Theory">nucl-th</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/PhysRevC.98.025801">10.1103/PhysRevC.98.025801 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Deep crustal heating by neutrinos from the surface of accreting neutron stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Fattoyev%2C+F+J">F. J. Fattoyev</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Cumming%2C+A">Andrew Cumming</a>, <a href="/search/astro-ph?searchtype=author&query=Deibel%2C+A">Alex Deibel</a>, <a href="/search/astro-ph?searchtype=author&query=Horowitz%2C+C+J">C. J. Horowitz</a>, <a href="/search/astro-ph?searchtype=author&query=Li%2C+B">Bao-An Li</a>, <a href="/search/astro-ph?searchtype=author&query=Lin%2C+Z">Zidu Lin</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="1710.10367v2-abstract-short" style="display: inline;"> We present a new mechanism for deep crustal heating in accreting neutron stars. Charged pions ($蟺^+$) are produced in nuclear collisions on the neutron star surface during active accretion and upon decay they provide a flux of neutrinos into the neutron star crust. For massive and/or compact neutron stars, neutrinos deposit $\approx 1\textrm{--} 2 \, \mathrm{MeV}$ of heat per accreted nucleon into… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1710.10367v2-abstract-full').style.display = 'inline'; document.getElementById('1710.10367v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1710.10367v2-abstract-full" style="display: none;"> We present a new mechanism for deep crustal heating in accreting neutron stars. Charged pions ($蟺^+$) are produced in nuclear collisions on the neutron star surface during active accretion and upon decay they provide a flux of neutrinos into the neutron star crust. For massive and/or compact neutron stars, neutrinos deposit $\approx 1\textrm{--} 2 \, \mathrm{MeV}$ of heat per accreted nucleon into the inner crust. The strength of neutrino heating is comparable to the previously known sources of deep crustal heating, such as from pycnonuclear fusion reactions, and is relevant for studies of cooling neutron stars. We model the thermal evolution of a transient neutron star in a low-mass X-ray binary, and in the particular case of the neutron star MXB~1659-29 we show that additional deep crustal heating requires a higher thermal conductivity for the neutron star inner crust. A better knowledge of pion production cross sections near threshold would improve the accuracy of our predictions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1710.10367v2-abstract-full').style.display = 'none'; document.getElementById('1710.10367v2-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, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 27 October, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 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">12 pages, 9 figures, 3 tables; [Added a new figure and edited the text in response to Referee's remarks and suggestions]</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. C 98, 025801 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1710.09365">arXiv:1710.09365</a> <span> [<a href="https://arxiv.org/pdf/1710.09365">pdf</a>, <a href="https://arxiv.org/format/1710.09365">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/aa9e03">10.3847/2041-8213/aa9e03 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Different accretion heating of the neutron star crust during multiple outbursts in MAXI J0556-332 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Parikh%2C+A+S">A. S. Parikh</a>, <a href="/search/astro-ph?searchtype=author&query=Homan%2C+J">J. Homan</a>, <a href="/search/astro-ph?searchtype=author&query=Wijnands%2C+R">R. Wijnands</a>, <a href="/search/astro-ph?searchtype=author&query=Ootes%2C+L+S">L. S. Ootes</a>, <a href="/search/astro-ph?searchtype=author&query=Page%2C+D">D. Page</a>, <a href="/search/astro-ph?searchtype=author&query=Degenaar%2C+D+A+N">D. Altamirano. N. Degenaar</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Cackett%2C+E+M">E. M. Cackett</a>, <a href="/search/astro-ph?searchtype=author&query=Cumming%2C+A">A. Cumming</a>, <a href="/search/astro-ph?searchtype=author&query=Deibel%2C+A">A. Deibel</a>, <a href="/search/astro-ph?searchtype=author&query=Fridriksson%2C+J+K">J. K. Fridriksson</a>, <a href="/search/astro-ph?searchtype=author&query=Lin%2C+D">D. Lin</a>, <a href="/search/astro-ph?searchtype=author&query=Linares%2C+M">M. Linares</a>, <a href="/search/astro-ph?searchtype=author&query=Miller%2C+J+M">J. M. Miller</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="1710.09365v2-abstract-short" style="display: inline;"> The transient neutron star (NS) low-mass X-ray binary MAXI J0556$-$332 provides a rare opportunity to study NS crust heating and subsequent cooling for multiple outbursts of the same source. We examine {\it MAXI}, {\it Swift}, {\it Chandra}, and {\it XMM-Newton} data of MAXI J0556$-$332 obtained during and after three accretion outbursts of different durations and brightness. We report on new data… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1710.09365v2-abstract-full').style.display = 'inline'; document.getElementById('1710.09365v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1710.09365v2-abstract-full" style="display: none;"> The transient neutron star (NS) low-mass X-ray binary MAXI J0556$-$332 provides a rare opportunity to study NS crust heating and subsequent cooling for multiple outbursts of the same source. We examine {\it MAXI}, {\it Swift}, {\it Chandra}, and {\it XMM-Newton} data of MAXI J0556$-$332 obtained during and after three accretion outbursts of different durations and brightness. We report on new data obtained after outburst III. The source has been tracked up to $\sim$1800 d after the end of outburst I. Outburst I heated the crust strongly, but no significant reheating was observed during outburst II. Cooling from $\sim$333 eV to $\sim$146 eV was observed during the first $\sim$1200 d. Outburst III reheated the crust up to $\sim$167 eV, after which the crust cooled again to $\sim$131 eV in $\sim$350 d. We model the thermal evolution of the crust and find that this source required a different strength and depth of shallow heating during each of the three outbursts. The shallow heating released during outburst I was $\sim$17 MeV nucleon$^{-1}$ and outburst III required $\sim$0.3 MeV nucleon$^{-1}$. These cooling observations could not be explained without shallow heating. The shallow heating for outburst II was not well constrained and could vary from $\sim$0--2.2 MeV nucleon$^{-1}$, i.e., this outburst could in principle be explained without invoking shallow heating. We discuss the nature of the shallow heating and why it may occur at different strengths and depths during different outbursts. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1710.09365v2-abstract-full').style.display = 'none'; document.getElementById('1710.09365v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 29 November, 2017; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 October, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication by ApJ Letters</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1611.07988">arXiv:1611.07988</a> <span> [<a href="https://arxiv.org/pdf/1611.07988">pdf</a>, <a href="https://arxiv.org/format/1611.07988">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> </div> <p class="title is-5 mathjax"> Direct Three-body Triple-$伪$ in Helium Novae </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Connolly%2C+R">Ryan Connolly</a>, <a href="/search/astro-ph?searchtype=author&query=Deibel%2C+A">Alex Deibel</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</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="1611.07988v1-abstract-short" style="display: inline;"> In AM CVn binaries, a white dwarf primary accretes material from a helium-rich white dwarf or stellar companion. The unstable ignition of nuclear burning via the $3伪$ reaction in an accumulated helium layer powers a thermonuclear runaway near accretion rates $\dot{M} \lesssim 10^{-6} \, \mathrm{M_{\odot} \ yr^{-1}}$ that may be observed as helium nova or .Ia supernova. Helium burning in the primar… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1611.07988v1-abstract-full').style.display = 'inline'; document.getElementById('1611.07988v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1611.07988v1-abstract-full" style="display: none;"> In AM CVn binaries, a white dwarf primary accretes material from a helium-rich white dwarf or stellar companion. The unstable ignition of nuclear burning via the $3伪$ reaction in an accumulated helium layer powers a thermonuclear runaway near accretion rates $\dot{M} \lesssim 10^{-6} \, \mathrm{M_{\odot} \ yr^{-1}}$ that may be observed as helium nova or .Ia supernova. Helium burning in the primary's envelope at temperatures $T \lesssim 10^{8} \, \mathrm{K}$ may proceed via the direct three-body fusion of $伪$-particles. Here we show that the direct three-body rate by Nguyen et al. (2012) -- which is reduced relative to the extrapolated resonant rate at temperatures $T \gtrsim 5 \times 10^{7} \, \mathrm{K}$ -- results in novae with longer recurrence times and larger ignition masses. By contrast, we find that the enhancement in the direct three-body rate at temperatures below $T \lesssim 5 \times 10^{7} \, \mathrm{K}$ does not result in significant differences in nova outburst properties. The most massive envelopes in our models are near the density threshold for detonation of the helium layer, where an increase in the density at ignition due to the $3伪$ rate may be important. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1611.07988v1-abstract-full').style.display = 'none'; document.getElementById('1611.07988v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 November, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 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">5 pages, 5 figures. Submitted to 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/1609.07155">arXiv:1609.07155</a> <span> [<a href="https://arxiv.org/pdf/1609.07155">pdf</a>, <a href="https://arxiv.org/format/1609.07155">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/aa6a19">10.3847/1538-4357/aa6a19 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Late time cooling of neutron star transients and the physics of the inner crust </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Deibel%2C+A">Alex Deibel</a>, <a href="/search/astro-ph?searchtype=author&query=Cumming%2C+A">Andrew Cumming</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Reddy%2C+S">Sanjay Reddy</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="1609.07155v1-abstract-short" style="display: inline;"> An accretion outburst onto a neutron star transient heats the neutron star's crust out of thermal equilibrium with the core. After the outburst the crust thermally relaxes toward equilibrium with the neutron star core and the surface thermal emission powers the quiescent X-ray light curve. Crust cooling models predict that thermal equilibrium of the crust will be established… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1609.07155v1-abstract-full').style.display = 'inline'; document.getElementById('1609.07155v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1609.07155v1-abstract-full" style="display: none;"> An accretion outburst onto a neutron star transient heats the neutron star's crust out of thermal equilibrium with the core. After the outburst the crust thermally relaxes toward equilibrium with the neutron star core and the surface thermal emission powers the quiescent X-ray light curve. Crust cooling models predict that thermal equilibrium of the crust will be established $\approx 1000 \, \mathrm{d}$ into quiescence. Recent observations of the cooling neutron star transient MXB 1659-29, however, suggest that the crust did not reach thermal equilibrium with the core on the predicted timescale and continued to cool after $\approx 2500 \, \mathrm{d}$ into quiescence. Because the quiescent light curve reveals successively deeper layers of the crust, the observed late time cooling of MXB 1659-29 depends on the thermal transport in the inner crust. In particular, the observed late time cooling is consistent with a low thermal conductivity layer near the depth predicted for nuclear pasta that maintains a temperature gradient between the neutron star's inner crust and core for thousands of days into quiescence. As a result, the temperature near the crust-core boundary remains above the critical temperature for neutron superfluidity and a layer of normal neutrons forms in the inner crust. We find that the late time cooling of MXB 1659-29 is consistent with heat release from a normal neutron layer near the crust-core boundary with a long thermal time. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1609.07155v1-abstract-full').style.display = 'none'; document.getElementById('1609.07155v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 September, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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">9 pages, 5 Figures. Submitted to ApJ</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> INT-PUB-16-025 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1608.07532">arXiv:1608.07532</a> <span> [<a href="https://arxiv.org/pdf/1608.07532">pdf</a>, <a href="https://arxiv.org/format/1608.07532">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="Nuclear Theory">nucl-th</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/PhysRevC.95.025806">10.1103/PhysRevC.95.025806 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A lower limit on the heat capacity of the neutron star core </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Cumming%2C+A">Andrew Cumming</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Fattoyev%2C+F+J">Farrukh J. Fattoyev</a>, <a href="/search/astro-ph?searchtype=author&query=Horowitz%2C+C+J">C. J. Horowitz</a>, <a href="/search/astro-ph?searchtype=author&query=Page%2C+D">Dany Page</a>, <a href="/search/astro-ph?searchtype=author&query=Reddy%2C+S">Sanjay Reddy</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="1608.07532v1-abstract-short" style="display: inline;"> We show that observations of the core temperature of transiently-accreting neutron stars combined with observations of an accretion outburst give a lower limit to the neutron star core heat capacity. For the neutron stars in the low mass X-ray binaries KS 1731-260, MXB 1659-29, and XTE J1701-462, we show that the lower limit is a factor of a few below the core heat capacity expected if neutrons an… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1608.07532v1-abstract-full').style.display = 'inline'; document.getElementById('1608.07532v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1608.07532v1-abstract-full" style="display: none;"> We show that observations of the core temperature of transiently-accreting neutron stars combined with observations of an accretion outburst give a lower limit to the neutron star core heat capacity. For the neutron stars in the low mass X-ray binaries KS 1731-260, MXB 1659-29, and XTE J1701-462, we show that the lower limit is a factor of a few below the core heat capacity expected if neutrons and protons in the core are paired, so that electrons provide the dominant contribution to the heat capacity. This limit rules out a core dominated by a quark color-flavor-locked (CFL) phase, which would have a much lower heat capacity. Future observations of or limits on cooling during quiescence will further constrain the core heat capacity. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1608.07532v1-abstract-full').style.display = 'none'; document.getElementById('1608.07532v1-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 August, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 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">14 pages, 10 figures, submitted to Physical Review C</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. C 95, 025806 (2017) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1608.03880">arXiv:1608.03880</a> <span> [<a href="https://arxiv.org/pdf/1608.03880">pdf</a>, <a href="https://arxiv.org/ps/1608.03880">ps</a>, <a href="https://arxiv.org/format/1608.03880">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/10.3847/1538-4357/833/2/186">10.3847/1538-4357/833/2/186 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The thermal state of KS 1731-260 after 14.5 years in quiescence </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Merritt%2C+R+L">Rachael L. Merritt</a>, <a href="/search/astro-ph?searchtype=author&query=Cackett%2C+E+M">Edward M. Cackett</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Page%2C+D">Dany Page</a>, <a href="/search/astro-ph?searchtype=author&query=Cumming%2C+A">Andrew Cumming</a>, <a href="/search/astro-ph?searchtype=author&query=Degenaar%2C+N">Nathalie Degenaar</a>, <a href="/search/astro-ph?searchtype=author&query=Deibel%2C+A">Alex Deibel</a>, <a href="/search/astro-ph?searchtype=author&query=Homan%2C+J">Jeroen Homan</a>, <a href="/search/astro-ph?searchtype=author&query=Miller%2C+J+M">Jon M. Miller</a>, <a href="/search/astro-ph?searchtype=author&query=Wijnands%2C+R">Rudy Wijnands</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="1608.03880v2-abstract-short" style="display: inline;"> Crustal cooling of accretion-heated neutron stars provides insight into the stellar interior of neutron stars. The neutron star X-ray transient, KS~1731$-$260, was in outburst for 12.5 years before returning to quiescence in 2001. We have monitored the cooling of this source since then through {\it Chandra} and {\it XMM-Newton} observations. Here, we present a 150 ks {\it Chandra} observation of K… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1608.03880v2-abstract-full').style.display = 'inline'; document.getElementById('1608.03880v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1608.03880v2-abstract-full" style="display: none;"> Crustal cooling of accretion-heated neutron stars provides insight into the stellar interior of neutron stars. The neutron star X-ray transient, KS~1731$-$260, was in outburst for 12.5 years before returning to quiescence in 2001. We have monitored the cooling of this source since then through {\it Chandra} and {\it XMM-Newton} observations. Here, we present a 150 ks {\it Chandra} observation of KS~1731$-$260 taken in August 2015, about 14.5 years into quiescence, and 6 years after the previous observation. We find that the neutron star surface temperature is consistent with the previous observation, suggesting that crustal cooling has likely stopped and the crust has reached thermal equilibrium with the core. Using a theoretical crust thermal evolution code, we fit the observed cooling curves and constrain the core temperature (T$_c = 9.35\pm0.25\times10^7$ K), composition (Q$_{imp} = 4.4^{+2.2}_{-0.5}$) and level of extra shallow heating required (Q$_{sh} = 1.36\pm0.18$ MeV/nucleon). We find that the presence of a low thermal conductivity layer, as expected from nuclear pasta, is not required to fit the cooling curve well, but cannot be excluded either. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1608.03880v2-abstract-full').style.display = 'none'; document.getElementById('1608.03880v2-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> 3 October, 2016; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 12 August, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 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">7 pages, 6 figures, 1 table, accepted to 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/1605.04878">arXiv:1605.04878</a> <span> [<a href="https://arxiv.org/pdf/1605.04878">pdf</a>, <a href="https://arxiv.org/format/1605.04878">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/0067-0049/225/1/3">10.3847/0067-0049/225/1/3 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Tracer Method for Computing Type Ia Supernova Yields: Burning Model Calibration, Reconstruction of Thickened Flames, and Verification for Planar Detonations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Townsley%2C+D+M">Dean M. Townsley</a>, <a href="/search/astro-ph?searchtype=author&query=Miles%2C+B+J">Broxton J. Miles</a>, <a href="/search/astro-ph?searchtype=author&query=Timmes%2C+F+X">F. X. Timmes</a>, <a href="/search/astro-ph?searchtype=author&query=Calder%2C+A+C">Alan C. Calder</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</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="1605.04878v1-abstract-short" style="display: inline;"> We refine our previously introduced parameterized model for explosive carbon-oxygen fusion during thermonuclear supernovae (SN Ia) by adding corrections to post-processing of recorded Lagrangian fluid element histories to obtain more accurate isotopic yields. Deflagration and detonation products are verified for propagation in a uniform density medium. A new method is introduced for reconstructing… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1605.04878v1-abstract-full').style.display = 'inline'; document.getElementById('1605.04878v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1605.04878v1-abstract-full" style="display: none;"> We refine our previously introduced parameterized model for explosive carbon-oxygen fusion during thermonuclear supernovae (SN Ia) by adding corrections to post-processing of recorded Lagrangian fluid element histories to obtain more accurate isotopic yields. Deflagration and detonation products are verified for propagation in a uniform density medium. A new method is introduced for reconstructing the temperature-density history within the artificially thick model deflagration front. We obtain better than 5\% consistency between the electron capture computed by the burning model and yields from post-processing. For detonations, we compare to a benchmark calculation of the structure of driven steady-state planar detonations performed with a large nuclear reaction network and error-controlled integration. We verify that, for steady-state planar detonations down to a density of 5x10^6 g/cc, our post processing matches the major abundances in the benchmark solution typically to better than 10% for times greater than 0.01 s after the shock front passage. As a test case to demonstrate the method, presented here with post-processing for the first time, we perform a two dimensional simulation of a SN Ia in the Chandrasekhar-mass deflagration-detonation transition (DDT) scenario. We find that reconstruction of deflagration tracks leads to slightly more complete silicon burning than without reconstruction. The resulting abundance structure of the ejecta is consistent with inferences from spectroscopic studies of observed SNe Ia. We confirm the absence of a central region of stable Fe-group material for the multi-dimensional DDT scenario. Detailed isotopic yields are tabulated and only change modestly when using deflagration reconstruction. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1605.04878v1-abstract-full').style.display = 'none'; document.getElementById('1605.04878v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 May, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 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">28 pages, 16 figures, Accepted to the Astrophysical Journal Supplemental</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1603.02213">arXiv:1603.02213</a> <span> [<a href="https://arxiv.org/pdf/1603.02213">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Nuclear Experiment">nucl-ex</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Nuclear Theory">nucl-th</span> </div> </div> <p class="title is-5 mathjax"> White Paper on Nuclear Astrophysics </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Arcones%2C+A">Almudena Arcones</a>, <a href="/search/astro-ph?searchtype=author&query=Bardayan%2C+D+W">Dan W. Bardayan</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=Berstein%2C+L+A">Lee A. Berstein</a>, <a href="/search/astro-ph?searchtype=author&query=Blackmon%2C+J+C">Jeffrey C. Blackmon</a>, <a href="/search/astro-ph?searchtype=author&query=Messer%2C+B">Bronson Messer</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+B+A">B. Alex Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Brune%2C+C+R">Carl R. Brune</a>, <a href="/search/astro-ph?searchtype=author&query=Champagne%2C+A+E">Art E. Champagne</a>, <a href="/search/astro-ph?searchtype=author&query=Chieffi%2C+A">Alessandro Chieffi</a>, <a href="/search/astro-ph?searchtype=author&query=Couture%2C+A+J">Aaron J. Couture</a>, <a href="/search/astro-ph?searchtype=author&query=Danielewicz%2C+P">Pawel Danielewicz</a>, <a href="/search/astro-ph?searchtype=author&query=Diehl%2C+R">Roland Diehl</a>, <a href="/search/astro-ph?searchtype=author&query=El-Eid%2C+M">Mounib El-Eid</a>, <a href="/search/astro-ph?searchtype=author&query=Escher%2C+J">Jutta Escher</a>, <a href="/search/astro-ph?searchtype=author&query=Fields%2C+B+D">Brian D. Fields</a>, <a href="/search/astro-ph?searchtype=author&query=Fr%C3%B6hlich%2C+C">Carla Fr枚hlich</a>, <a href="/search/astro-ph?searchtype=author&query=Herwig%2C+F">Falk Herwig</a>, <a href="/search/astro-ph?searchtype=author&query=Hix%2C+W+R">William Raphael Hix</a>, <a href="/search/astro-ph?searchtype=author&query=Iliadis%2C+C">Christian Iliadis</a>, <a href="/search/astro-ph?searchtype=author&query=Lynch%2C+W+G">William G. Lynch</a>, <a href="/search/astro-ph?searchtype=author&query=McLaughlin%2C+G+C">Gail C. McLaughlin</a>, <a href="/search/astro-ph?searchtype=author&query=Meyer%2C+B+S">Bradley S. Meyer</a>, <a href="/search/astro-ph?searchtype=author&query=Mezzacappa%2C+A">Anthony Mezzacappa</a> , et al. (18 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1603.02213v2-abstract-short" style="display: inline;"> This white paper informs the nuclear astrophysics community and funding agencies about the scientific directions and priorities of the field and provides input from this community for the 2015 Nuclear Science Long Range Plan. It summarizes the outcome of the nuclear astrophysics town meeting that was held on August 21-23, 2014 in College Station at the campus of Texas A&M University in preparation… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1603.02213v2-abstract-full').style.display = 'inline'; document.getElementById('1603.02213v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1603.02213v2-abstract-full" style="display: none;"> This white paper informs the nuclear astrophysics community and funding agencies about the scientific directions and priorities of the field and provides input from this community for the 2015 Nuclear Science Long Range Plan. It summarizes the outcome of the nuclear astrophysics town meeting that was held on August 21-23, 2014 in College Station at the campus of Texas A&M University in preparation of the NSAC Nuclear Science Long Range Plan. It also reflects the outcome of an earlier town meeting of the nuclear astrophysics community organized by the Joint Institute for Nuclear Astrophysics (JINA) on October 9- 10, 2012 Detroit, Michigan, with the purpose of developing a vision for nuclear astrophysics in light of the recent NRC decadal surveys in nuclear physics (NP2010) and astronomy (ASTRO2010). The white paper is furthermore informed by the town meeting of the Association of Research at University Nuclear Accelerators (ARUNA) that took place at the University of Notre Dame on June 12-13, 2014. In summary we find that nuclear astrophysics is a modern and vibrant field addressing fundamental science questions at the intersection of nuclear physics and astrophysics. These questions relate to the origin of the elements, the nuclear engines that drive life and death of stars, and the properties of dense matter. A broad range of nuclear accelerator facilities, astronomical observatories, theory efforts, and computational capabilities are needed. With the developments outlined in this white paper, answers to long standing key questions are well within reach in the coming decade. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1603.02213v2-abstract-full').style.display = 'none'; document.getElementById('1603.02213v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 March, 2016; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 4 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">131 pages, community white paper based on 2012 JINA Town Meeting in Detroit, MI, and 2014 APS Town Meeting in College Station, TX, corrected author names</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1603.01281">arXiv:1603.01281</a> <span> [<a href="https://arxiv.org/pdf/1603.01281">pdf</a>, <a href="https://arxiv.org/format/1603.01281">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/10.3847/0004-637X/831/1/13">10.3847/0004-637X/831/1/13 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Urca cooling pairs in the neutron star ocean and their effect on superbursts </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Deibel%2C+A">Alex Deibel</a>, <a href="/search/astro-ph?searchtype=author&query=Meisel%2C+Z">Zach Meisel</a>, <a href="/search/astro-ph?searchtype=author&query=Schatz%2C+H">Hendrik Schatz</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Cumming%2C+A">Andrew Cumming</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="1603.01281v2-abstract-short" style="display: inline;"> An accretion outburst onto a neutron star deposits hydrogen-rich and/or helium-rich material into the neutron star's envelope. Thermonuclear burning of accreted material robustly produces Urca pairs\textrm{---}pairs of nuclei that undergo cycles of $e^-$-capture and $尾^-$-decay. The strong $T^5$ dependence of the Urca cooling neutrino luminosity means that Urca pairs in the neutron star interior p… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1603.01281v2-abstract-full').style.display = 'inline'; document.getElementById('1603.01281v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1603.01281v2-abstract-full" style="display: none;"> An accretion outburst onto a neutron star deposits hydrogen-rich and/or helium-rich material into the neutron star's envelope. Thermonuclear burning of accreted material robustly produces Urca pairs\textrm{---}pairs of nuclei that undergo cycles of $e^-$-capture and $尾^-$-decay. The strong $T^5$ dependence of the Urca cooling neutrino luminosity means that Urca pairs in the neutron star interior potentially remove heat from accretion-driven nuclear reactions. In this study, we identify Urca pairs in the neutron star's ocean \textrm{---} a plasma of ions and electrons overlaying the neutron star crust \textrm{---} and demonstrate that Urca cooling occurs at all depths in the ocean. We find that Urca pairs in the ocean and crust lower the ocean's steady-state temperature during an accretion outburst and that unstable carbon ignition, which is thought to trigger superbursts, occurs deeper than it would otherwise. Cooling superburst light curves, however, are only marginally impacted by cooling from Urca pairs because the superburst peak radiative luminosity $L_{\rm peak}$ is always much greater than the Urca pair neutrino luminosity $L_谓$ in the hot post-superburst ocean. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1603.01281v2-abstract-full').style.display = 'none'; document.getElementById('1603.01281v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 10 November, 2016; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 3 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">9 pages, 6 Figures, accepted to the Astrophysical 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/1512.06129">arXiv:1512.06129</a> <span> [<a href="https://arxiv.org/pdf/1512.06129">pdf</a>, <a href="https://arxiv.org/ps/1512.06129">ps</a>, <a href="https://arxiv.org/format/1512.06129">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/stv2959">10.1093/mnras/stv2959 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Constraining the properties of neutron star crusts with the transient low-mass X-ray binary Aql X-1 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Waterhouse%2C+A+C">A. C. Waterhouse</a>, <a href="/search/astro-ph?searchtype=author&query=Degenaar%2C+N">N. Degenaar</a>, <a href="/search/astro-ph?searchtype=author&query=Wijnands%2C+R">R. Wijnands</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Miller%2C+J+M">J. M. Miller</a>, <a href="/search/astro-ph?searchtype=author&query=Altamirano%2C+D">D. Altamirano</a>, <a href="/search/astro-ph?searchtype=author&query=Linares%2C+M">M. Linares</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="1512.06129v1-abstract-short" style="display: inline;"> Aql X-1 is a prolific transient neutron star low-mass X-ray binary that exhibits an accretion outburst approximately once every year. Whether the thermal X-rays detected in intervening quiescent episodes are the result of cooling of the neutron star or due to continued low-level accretion remains unclear. In this work we use Swift data obtained after the long and bright 2011 and 2013 outbursts, as… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1512.06129v1-abstract-full').style.display = 'inline'; document.getElementById('1512.06129v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1512.06129v1-abstract-full" style="display: none;"> Aql X-1 is a prolific transient neutron star low-mass X-ray binary that exhibits an accretion outburst approximately once every year. Whether the thermal X-rays detected in intervening quiescent episodes are the result of cooling of the neutron star or due to continued low-level accretion remains unclear. In this work we use Swift data obtained after the long and bright 2011 and 2013 outbursts, as well as the short and faint 2015 outburst, to investigate the hypothesis that cooling of the accretion-heated neutron star crust dominates the quiescent thermal emission in Aql X-1. We demonstrate that the X-ray light curves and measured neutron star surface temperatures are consistent with the expectations of the crust cooling paradigm. By using a thermal evolution code, we find that ~1.2-3.2 MeV/nucleon of shallow heat release describes the observational data well, depending on the assumed mass-accretion rate and temperature of the stellar core. We find no evidence for varying strengths of this shallow heating after different outbursts, but this could be due to limitations of the data. We argue that monitoring Aql X-1 for up to ~1 year after future outbursts can be a powerful tool to break model degeneracies and solve open questions about the magnitude, depth and origin of shallow heating in neutron star crusts. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1512.06129v1-abstract-full').style.display = 'none'; document.getElementById('1512.06129v1-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 December, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2015. </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, 5 figures, 3 tables, accepted to MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1510.07515">arXiv:1510.07515</a> <span> [<a href="https://arxiv.org/pdf/1510.07515">pdf</a>, <a href="https://arxiv.org/format/1510.07515">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Nuclear Theory">nucl-th</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/10.1140/epja/i2016-16018-1">10.1140/epja/i2016-16018-1 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Neutron Star Radii, Universal Relations, and the Role of Prior Distributions </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Steiner%2C+A+W">A. W. Steiner</a>, <a href="/search/astro-ph?searchtype=author&query=Lattimer%2C+J+M">J. M. Lattimer</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</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="1510.07515v1-abstract-short" style="display: inline;"> We investigate constraints on neutron star structure arising from the assumptions that neutron stars have crusts, that recent calculations of pure neutron matter limit the equation of state of neutron star matter near the nuclear saturation density, that the high-density equation of state is limited by causality and the largest high-accuracy neutron star mass measurement, and that general relativi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1510.07515v1-abstract-full').style.display = 'inline'; document.getElementById('1510.07515v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1510.07515v1-abstract-full" style="display: none;"> We investigate constraints on neutron star structure arising from the assumptions that neutron stars have crusts, that recent calculations of pure neutron matter limit the equation of state of neutron star matter near the nuclear saturation density, that the high-density equation of state is limited by causality and the largest high-accuracy neutron star mass measurement, and that general relativity is the correct theory of gravity. We explore the role of prior assumptions by considering two classes of equation of state models. In a first, the intermediate- and high-density behavior of the equation of state is parameterized by piecewise polytropes. In the second class, the high-density behavior of the equation of state is parameterized by piecewise continuous line segments. The smallest density at which high-density matter appears is varied in order to allow for strong phase transitions above the nuclear saturation density. We critically examine correlations among the pressure of matter, radii, maximum masses, the binding energy, the moment of inertia, and the tidal deformability, paying special attention to the sensitivity of these correlations to prior assumptions about the equation of state. It is possible to constrain the radii of $1.4~\mathrm{M}_{\odot}$ neutron stars to a be larger than 10 km, even without consideration of additional astrophysical observations, for example, those from photospheric radius expansion bursts or quiescent low-mass X-ray binaries. We are able to improve the accuracy of known correlations between the moment of inertia and compactness as well as the binding energy and compactness. We also demonstrate the existence of a correlation between the neutron star binding energy and the moment of inertia. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1510.07515v1-abstract-full').style.display = 'none'; document.getElementById('1510.07515v1-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 October, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2015. </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">Eur. Phys. J. A (in press)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Eur. Phys. J. A 52 (2016) 18 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1508.05961">arXiv:1508.05961</a> <span> [<a href="https://arxiv.org/pdf/1508.05961">pdf</a>, <a href="https://arxiv.org/format/1508.05961">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/0004-637X/824/1/59">10.3847/0004-637X/824/1/59 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> On Measuring the Metallicity of a Type Ia Supernova's Progenitor </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Miles%2C+B+J">Broxton J. Miles</a>, <a href="/search/astro-ph?searchtype=author&query=van+Rossum%2C+D+R">Daniel R. van Rossum</a>, <a href="/search/astro-ph?searchtype=author&query=Townsley%2C+D+M">Dean M. Townsley</a>, <a href="/search/astro-ph?searchtype=author&query=Timmes%2C+F+X">F. X. Timmes</a>, <a href="/search/astro-ph?searchtype=author&query=Jackson%2C+A+P">Aaron P. Jackson</a>, <a href="/search/astro-ph?searchtype=author&query=Calder%2C+A+C">Alan C. Calder</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</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="1508.05961v2-abstract-short" style="display: inline;"> In Type Ia Supernovae (\sneia), the relative abundances of chemical elements are affected by the neutron excess in the composition of the progenitor white dwarf. Since these products leave signatures in the spectra near maximum light, spectral features may be used to constrain the composition of the progenitor. We calculate the nucleosynthetic yields for three \snia simulations, assuming single de… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1508.05961v2-abstract-full').style.display = 'inline'; document.getElementById('1508.05961v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1508.05961v2-abstract-full" style="display: none;"> In Type Ia Supernovae (\sneia), the relative abundances of chemical elements are affected by the neutron excess in the composition of the progenitor white dwarf. Since these products leave signatures in the spectra near maximum light, spectral features may be used to constrain the composition of the progenitor. We calculate the nucleosynthetic yields for three \snia simulations, assuming single degenerate, Chandrasekhar mass progenitors, for a wide range of progenitor metallicities, and calculate synthetic light curves and spectra to explore correlations between progenitor metallicity and the strength of spectral features. We use two 2D simulations of the deflagration-detonation-transition scenario with different $^{56}$Ni yields and the W7 simulation to control for differences between explosion models and total yields. While the overall yields of intermediate mass elements (16 $<$ A $\leq$ 40) differ between the three cases, trends in the yields are similar. With increasing metallicity, $^{28}$Si yields remain nearly constant, $^{40}$Ca yields decline, and Ti and $^{54}$Fe yields increase. In the synthetic spectra, we identify two features at 30 days post explosion that appear to deepen with progenitor metallicity: a Ti feature around 4200\,脜 and a Fe feature around 5200\,脜\@. In all three simulations, their pseudo equivalent widths show a systematic trend with progenitor metallicity. This suggests that these two features may allow differentiation among progenitor metallicities of observed \sneia and potentially help reduce the intrinsic Hubble scatter. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1508.05961v2-abstract-full').style.display = 'none'; document.getElementById('1508.05961v2-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> 3 May, 2016; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 24 August, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2015. </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, 18 figures, accepted by the Astrophysical 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/1506.03846">arXiv:1506.03846</a> <span> [<a href="https://arxiv.org/pdf/1506.03846">pdf</a>, <a href="https://arxiv.org/format/1506.03846">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/10.1088/2041-8205/809/2/L31">10.1088/2041-8205/809/2/L31 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A strong shallow heat source in the accreting neutron star MAXI J0556-332 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Deibel%2C+A">Alex Deibel</a>, <a href="/search/astro-ph?searchtype=author&query=Cumming%2C+A">Andrew Cumming</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Page%2C+D">Dany Page</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="1506.03846v1-abstract-short" style="display: inline;"> An accretion outburst in an X-ray transient deposits material onto the neutron star primary; this accumulation of matter induces reactions in the neutron star's crust. During the accretion outburst these reactions heat the crust out of thermal equilibrium with the core. When accretion halts, the crust cools to its long-term equilibrium temperature on observable timescales. Here we examine the accr… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1506.03846v1-abstract-full').style.display = 'inline'; document.getElementById('1506.03846v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1506.03846v1-abstract-full" style="display: none;"> An accretion outburst in an X-ray transient deposits material onto the neutron star primary; this accumulation of matter induces reactions in the neutron star's crust. During the accretion outburst these reactions heat the crust out of thermal equilibrium with the core. When accretion halts, the crust cools to its long-term equilibrium temperature on observable timescales. Here we examine the accreting neutron star transient MAXI J0556-332, which is the hottest transient, at the start of quiescence, observed to date. Models of the quiescent light curve require a large deposition of heat in the shallow outer crust from an unknown source. The additional heat injected is $\approx 4\textrm{-}10\,\mathrm{MeV}$ per accreted nucleon; when the observed decline in accretion rate at the end of the outburst is accounted for, the required heating increases to $\approx 6\textrm{-}16\,\mathrm{MeV}$. This shallow heating is still required to fit the lightcurve even after taking into account a second accretion episode, uncertainties in distance, and different surface gravities. The amount of shallow heating is larger than that inferred for other neutron star transients and is larger than can be supplied by nuclear reactions or compositionally driven convection; but it is consistent with stored mechanical energy in the accretion disk. The high crust temperature ($T_b \gtrsim 10^{9} \, {\rm K}$) makes its cooling behavior in quiescence largely independent of the crust composition and envelope properties, so that future observations will probe the gravity of the source. Fits to the lightcurve disfavor the presence of Urca cooling pairs in the crust. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1506.03846v1-abstract-full').style.display = 'none'; document.getElementById('1506.03846v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 11 June, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2015. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">6 pages, 4 figures, submitted to ApJL</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1505.01862">arXiv:1505.01862</a> <span> [<a href="https://arxiv.org/pdf/1505.01862">pdf</a>, <a href="https://arxiv.org/ps/1505.01862">ps</a>, <a href="https://arxiv.org/format/1505.01862">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> Neutron star crust cooling in the Terzan 5 X-ray transient Swift J174805.3-244637 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Degenaar%2C+N">N. Degenaar</a>, <a href="/search/astro-ph?searchtype=author&query=Wijnands%2C+R">R. Wijnands</a>, <a href="/search/astro-ph?searchtype=author&query=Bahramian%2C+A">A. Bahramian</a>, <a href="/search/astro-ph?searchtype=author&query=Sivakoff%2C+G+R">G. R. Sivakoff</a>, <a href="/search/astro-ph?searchtype=author&query=Heinke%2C+C+O">C. O. Heinke</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Fridriksson%2C+J+K">J. K. Fridriksson</a>, <a href="/search/astro-ph?searchtype=author&query=Homan%2C+J">J. Homan</a>, <a href="/search/astro-ph?searchtype=author&query=Cackett%2C+E+M">E. M. Cackett</a>, <a href="/search/astro-ph?searchtype=author&query=Cumming%2C+A">A. Cumming</a>, <a href="/search/astro-ph?searchtype=author&query=Miller%2C+J+M">J. M. Miller</a>, <a href="/search/astro-ph?searchtype=author&query=Altamirano%2C+D">D. Altamirano</a>, <a href="/search/astro-ph?searchtype=author&query=Pooley%2C+D">D. Pooley</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="1505.01862v2-abstract-short" style="display: inline;"> When neutron stars reside in transient X-ray binaries, their crustal layers become heated during accretion outbursts and subsequently cool in quiescence. Observing and modeling this thermal response has yielded valuable insight into the physics of neutron star crusts. However, one unresolved problem is the evidence in several neutron stars for an extra energy source, located at shallow depth in th… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1505.01862v2-abstract-full').style.display = 'inline'; document.getElementById('1505.01862v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1505.01862v2-abstract-full" style="display: none;"> When neutron stars reside in transient X-ray binaries, their crustal layers become heated during accretion outbursts and subsequently cool in quiescence. Observing and modeling this thermal response has yielded valuable insight into the physics of neutron star crusts. However, one unresolved problem is the evidence in several neutron stars for an extra energy source, located at shallow depth in the crust, that is not accounted for by standard heating models. Its origin remains puzzling, and it is currently unclear whether this additional heating occurs in all neutron stars, and if the magnitude is always the same. Here, we report on Chandra observations that cover two years after the 2012 outburst of the transient neutron star X-ray binary Swift J174805.3-244637 in the globular cluster Terzan 5. The temperature of the neutron star was elevated during the first two months following its ~8 week accretion episode, but had decayed to the pre-outburst level within ~100 days. Interpreting this as rapid cooling of the accretion-heated crust, we model the observed temperature curve with a thermal evolution code. We find that there is no need to invoke shallow heating for this neutron star, although an extra energy release up to ~1.4 MeV/nucleon is allowed by the current data (2-sigma confidence). We also present two new data points on the crust cooling curve of the 11-Hz X-ray pulsar IGR J17480-2446 in Terzan 5, which was active in 2010. The temperature of this neutron star remained significantly above its pre-outburst level, but we detect no temperature change since the previous measurements of 2013 February. This is consistent with the slower cooling expected several years post-outburst. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1505.01862v2-abstract-full').style.display = 'none'; document.getElementById('1505.01862v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 May, 2015; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 7 May, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2015. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">11 pages, 6 figures, 5 tables, MNRAS in press. Minor (textual) changes to match published version</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1501.02776">arXiv:1501.02776</a> <span> [<a href="https://arxiv.org/pdf/1501.02776">pdf</a>, <a href="https://arxiv.org/format/1501.02776">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> The LOFT perspective on neutron star thermonuclear bursts </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Zand%2C+J+J+M+i+%27">J. J. M. in 't Zand</a>, <a href="/search/astro-ph?searchtype=author&query=Altamirano%2C+D">D. Altamirano</a>, <a href="/search/astro-ph?searchtype=author&query=Ballantyne%2C+D+R">D. R. Ballantyne</a>, <a href="/search/astro-ph?searchtype=author&query=Bhattacharyya%2C+S">S. Bhattacharyya</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Cavecchi%2C+Y">Y. Cavecchi</a>, <a href="/search/astro-ph?searchtype=author&query=Chakrabarty%2C+D">D. Chakrabarty</a>, <a href="/search/astro-ph?searchtype=author&query=Chenevez%2C+J">J. Chenevez</a>, <a href="/search/astro-ph?searchtype=author&query=Cumming%2C+A">A. Cumming</a>, <a href="/search/astro-ph?searchtype=author&query=Degenaar%2C+N">N. Degenaar</a>, <a href="/search/astro-ph?searchtype=author&query=Falanga%2C+M">M. Falanga</a>, <a href="/search/astro-ph?searchtype=author&query=Galloway%2C+D+K">D. K. Galloway</a>, <a href="/search/astro-ph?searchtype=author&query=Heger%2C+A">A. Heger</a>, <a href="/search/astro-ph?searchtype=author&query=Jos%C3%A9%2C+J">J. Jos茅</a>, <a href="/search/astro-ph?searchtype=author&query=Keek%2C+L">L. Keek</a>, <a href="/search/astro-ph?searchtype=author&query=Linares%2C+M">M. Linares</a>, <a href="/search/astro-ph?searchtype=author&query=Mahmoodifar%2C+S">S. Mahmoodifar</a>, <a href="/search/astro-ph?searchtype=author&query=Malone%2C+C+M">C. M. Malone</a>, <a href="/search/astro-ph?searchtype=author&query=M%C3%A9ndez%2C+M">M. M茅ndez</a>, <a href="/search/astro-ph?searchtype=author&query=Miller%2C+M+C">M. C. Miller</a>, <a href="/search/astro-ph?searchtype=author&query=Paerels%2C+F+B+S">F. B. S. Paerels</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">J. Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=R%C3%B3zanska%2C+A">A. R贸zanska</a>, <a href="/search/astro-ph?searchtype=author&query=Schatz%2C+H">H. Schatz</a>, <a href="/search/astro-ph?searchtype=author&query=Serino%2C+M">M. Serino</a> , et al. (9 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="1501.02776v1-abstract-short" style="display: inline;"> This is a White Paper in support of the mission concept of the Large Observatory for X-ray Timing (LOFT), proposed as a medium-sized ESA mission. We discuss the potential of LOFT for the study of thermonuclear X-ray bursts on accreting neutron stars. For a summary, we refer to the paper. </span> <span class="abstract-full has-text-grey-dark mathjax" id="1501.02776v1-abstract-full" style="display: none;"> This is a White Paper in support of the mission concept of the Large Observatory for X-ray Timing (LOFT), proposed as a medium-sized ESA mission. We discuss the potential of LOFT for the study of thermonuclear X-ray bursts on accreting neutron stars. For a summary, we refer to the paper. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1501.02776v1-abstract-full').style.display = 'none'; document.getElementById('1501.02776v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 January, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2015. </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">White Paper in Support of the Mission Concept of the Large Observatory for X-ray Timing</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1405.3541">arXiv:1405.3541</a> <span> [<a href="https://arxiv.org/pdf/1405.3541">pdf</a>, <a href="https://arxiv.org/format/1405.3541">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/10.1088/0004-637X/791/2/106">10.1088/0004-637X/791/2/106 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Carbon Synthesis in Steady-State Hydrogen and Helium Burning On Accreting Neutron Stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Stevens%2C+J">Jeremy Stevens</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Cumming%2C+A">Andrew Cumming</a>, <a href="/search/astro-ph?searchtype=author&query=Cyburt%2C+R">Richard Cyburt</a>, <a href="/search/astro-ph?searchtype=author&query=Schatz%2C+H">Hendrik Schatz</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="1405.3541v1-abstract-short" style="display: inline;"> Superbursts from accreting neutron stars probe nuclear reactions at extreme densities ($蟻\approx 10^{9}~g\,cm^{-3}$) and temperatures ($T>10^9~K$). These bursts ($\sim$1000 times more energetic than type I X-ray bursts) are most likely triggered by unstable ignition of carbon in a sea of heavy nuclei made during the rp-process of regular type I X-ray bursts (where the accumulated hydrogen and heli… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1405.3541v1-abstract-full').style.display = 'inline'; document.getElementById('1405.3541v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1405.3541v1-abstract-full" style="display: none;"> Superbursts from accreting neutron stars probe nuclear reactions at extreme densities ($蟻\approx 10^{9}~g\,cm^{-3}$) and temperatures ($T>10^9~K$). These bursts ($\sim$1000 times more energetic than type I X-ray bursts) are most likely triggered by unstable ignition of carbon in a sea of heavy nuclei made during the rp-process of regular type I X-ray bursts (where the accumulated hydrogen and helium are burned). An open question is the origin of sufficient amounts of carbon, which is largely destroyed during the rp-process in X-ray bursts. We explore carbon production in steady-state burning via the rp-process, which might occur together with unstable burning in systems showing superbursts. We find that for a wide range of accretion rates and accreted helium mass fractions large amounts of carbon are produced, even for systems that accrete solar composition. This makes stable hydrogen and helium burning a viable source of carbon to trigger superbursts. We also investigate the sensitivity of the results to nuclear reactions. We find that the $^{14}$O($伪$,p)$^{17}$F reaction rate introduces by far the largest uncertainties in the $^{12}$C yield. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1405.3541v1-abstract-full').style.display = 'none'; document.getElementById('1405.3541v1-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, 2014; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2014. </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">8 pages, submitted to 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/1403.2385">arXiv:1403.2385</a> <span> [<a href="https://arxiv.org/pdf/1403.2385">pdf</a>, <a href="https://arxiv.org/ps/1403.2385">ps</a>, <a href="https://arxiv.org/format/1403.2385">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/791/1/47">10.1088/0004-637X/791/1/47 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Probing the Crust of the Neutron Star in EXO 0748-676 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Degenaar%2C+N">N. Degenaar</a>, <a href="/search/astro-ph?searchtype=author&query=Medin%2C+Z">Z. Medin</a>, <a href="/search/astro-ph?searchtype=author&query=Cumming%2C+A">A. Cumming</a>, <a href="/search/astro-ph?searchtype=author&query=Wijnands%2C+R">R. Wijnands</a>, <a href="/search/astro-ph?searchtype=author&query=Wolff%2C+M+T">M. T. Wolff</a>, <a href="/search/astro-ph?searchtype=author&query=Cackett%2C+E+M">E. M. Cackett</a>, <a href="/search/astro-ph?searchtype=author&query=Miller%2C+J+M">J. M. Miller</a>, <a href="/search/astro-ph?searchtype=author&query=Jonker%2C+P+G">P. G. Jonker</a>, <a href="/search/astro-ph?searchtype=author&query=Homan%2C+J">J. Homan</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</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="1403.2385v2-abstract-short" style="display: inline;"> X-ray observations of quiescent X-ray binaries have the potential to provide insight into the structure and the composition of neutron stars. EXO 0748-676 had been actively accreting for over 24 yr before its outburst ceased in late 2008. Subsequent X-ray monitoring revealed a gradual decay of the quiescent thermal emission that can be attributed to cooling of the accretion-heated neutron star cru… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1403.2385v2-abstract-full').style.display = 'inline'; document.getElementById('1403.2385v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1403.2385v2-abstract-full" style="display: none;"> X-ray observations of quiescent X-ray binaries have the potential to provide insight into the structure and the composition of neutron stars. EXO 0748-676 had been actively accreting for over 24 yr before its outburst ceased in late 2008. Subsequent X-ray monitoring revealed a gradual decay of the quiescent thermal emission that can be attributed to cooling of the accretion-heated neutron star crust. In this work, we report on new Chandra and Swift observations that extend the quiescent monitoring to ~5 yr post-outburst. We find that the neutron star temperature remained at ~117 eV between 2009 and 2011, but had decreased to ~110 eV in 2013. This suggests that the crust has not fully cooled yet, which is supported by the lower temperature of ~95 eV that was measured ~4 yr prior to the accretion phase in 1980. Comparing the data to thermal evolution simulations reveals that the apparent lack of cooling between 2009 and 2011 could possibly be a signature of convection driven by phase separation of light and heavy nuclei in the outer layers of the neutron star. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1403.2385v2-abstract-full').style.display = 'none'; document.getElementById('1403.2385v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 10 July, 2014; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 10 March, 2014; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2014. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">9 pages, 4 tables, 3 figures. Minor revisions according to referee report. Accepted to 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/1401.5839">arXiv:1401.5839</a> <span> [<a href="https://arxiv.org/pdf/1401.5839">pdf</a>, <a href="https://arxiv.org/format/1401.5839">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Nuclear Theory">nucl-th</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="Nuclear Experiment">nucl-ex</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/10.1088/0954-3899/41/9/093001">10.1088/0954-3899/41/9/093001 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A way forward in the study of the symmetry energy: experiment, theory, and observation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Horowitz%2C+C+J">C. J. Horowitz</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Kim%2C+Y">Y. Kim</a>, <a href="/search/astro-ph?searchtype=author&query=Lynch%2C+W+G">W. G. Lynch</a>, <a href="/search/astro-ph?searchtype=author&query=Michaels%2C+R">R. Michaels</a>, <a href="/search/astro-ph?searchtype=author&query=Ono%2C+A">A. Ono</a>, <a href="/search/astro-ph?searchtype=author&query=Piekarewicz%2C+J">J. Piekarewicz</a>, <a href="/search/astro-ph?searchtype=author&query=Tsang%2C+M+B">M. B. Tsang</a>, <a href="/search/astro-ph?searchtype=author&query=Wolter%2C+H+H">H. H. Wolter</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="1401.5839v1-abstract-short" style="display: inline;"> The symmetry energy describes how the energy of nuclear matter rises as one goes away from equal numbers of neutrons and protons. This is very important to describe neutron rich matter in astrophysics. This article reviews our knowledge of the symmetry energy from theoretical calculations, nuclear structure measurements, heavy ion collisions, and astronomical observations. We then present a roadma… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1401.5839v1-abstract-full').style.display = 'inline'; document.getElementById('1401.5839v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1401.5839v1-abstract-full" style="display: none;"> The symmetry energy describes how the energy of nuclear matter rises as one goes away from equal numbers of neutrons and protons. This is very important to describe neutron rich matter in astrophysics. This article reviews our knowledge of the symmetry energy from theoretical calculations, nuclear structure measurements, heavy ion collisions, and astronomical observations. We then present a roadmap to make progress in areas of relevance to the symmetry energy that promotes collaboration between the astrophysics and the nuclear physics communities. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1401.5839v1-abstract-full').style.display = 'none'; document.getElementById('1401.5839v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 January, 2014; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2014. </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, results from first International Collaborations in Nuclear Theory (ICNT) program at NSCL/FRIB, submitted to J. Phys G</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> J. Phys. G: Nucl. Part. Phys. 41 (2014) 093001 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1312.2513">arXiv:1312.2513</a> <span> [<a href="https://arxiv.org/pdf/1312.2513">pdf</a>, <a href="https://arxiv.org/format/1312.2513">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/nature12757">10.1038/nature12757 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Strong neutrino cooling by cycles of electron capture and $尾^-$ decay in neutron star crusts </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Schatz%2C+H">Hendrik Schatz</a>, <a href="/search/astro-ph?searchtype=author&query=Gupta%2C+S">Sanjib Gupta</a>, <a href="/search/astro-ph?searchtype=author&query=M%C3%B6ller%2C+P">Peter M枚ller</a>, <a href="/search/astro-ph?searchtype=author&query=Beard%2C+M">Mary Beard</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Deibel%2C+A+T">Alex T. Deibel</a>, <a href="/search/astro-ph?searchtype=author&query=Gasques%2C+L+R">Leandro R. Gasques</a>, <a href="/search/astro-ph?searchtype=author&query=Hix%2C+W+R">William Raphael Hix</a>, <a href="/search/astro-ph?searchtype=author&query=Keek%2C+L">Laurens Keek</a>, <a href="/search/astro-ph?searchtype=author&query=Lau%2C+R">Rita Lau</a>, <a href="/search/astro-ph?searchtype=author&query=Steiner%2C+A+W">Andrew W. Steiner</a>, <a href="/search/astro-ph?searchtype=author&query=Wiescher%2C+M">Michael Wiescher</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="1312.2513v1-abstract-short" style="display: inline;"> The temperature in the crust of an accreting neutron star, which comprises its outermost kilometer, is set by heating from nuclear reactions at large densities, neutrino cooling, and heat transport from the interior. The heated crust has been thought to affect observable phenomena at shallower depths, such as thermonuclear bursts in the accreted envelope. Here we report that cycles of electron cap… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1312.2513v1-abstract-full').style.display = 'inline'; document.getElementById('1312.2513v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1312.2513v1-abstract-full" style="display: none;"> The temperature in the crust of an accreting neutron star, which comprises its outermost kilometer, is set by heating from nuclear reactions at large densities, neutrino cooling, and heat transport from the interior. The heated crust has been thought to affect observable phenomena at shallower depths, such as thermonuclear bursts in the accreted envelope. Here we report that cycles of electron capture and its inverse, $尾^-$ decay, involving neutron-rich nuclei at a typical depth of about 150 m, cool the outer neutron star crust by emitting neutrinos while also thermally decoupling the surface layers from the deeper crust. This Urca mechanism has been studied in the context of white dwarfs and Type Ia supernovae, but hitherto was not considered in neutron stars, because previous models computed the crust reactions using a zero-temperature approximation and assumed that only a single nuclear species was present at any given depth. This thermal decoupling means that X-ray bursts and other surface phenomena are largely independent of the strength of deep crustal heating. The unexpectedly short recurrence times, of the order of years, observed for very energetic thermonuclear superbursts are therefore not an indicator of a hot crust, but may point instead to an unknown local heating mechanism near the neutron star surface. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1312.2513v1-abstract-full').style.display = 'none'; document.getElementById('1312.2513v1-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 December, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 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">15 pages with 5 figures. Nature advance online publication, December 1, 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/1310.5622">arXiv:1310.5622</a> <span> [<a href="https://arxiv.org/pdf/1310.5622">pdf</a>, <a href="https://arxiv.org/ps/1310.5622">ps</a>, <a href="https://arxiv.org/format/1310.5622">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/epjconf/20136406007">10.1051/epjconf/20136406007 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> X-ray and UV correlation in the quiescent emission of Cen X-4, evidence of accretion and reprocessing </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Bernardini%2C+F">F. Bernardini</a>, <a href="/search/astro-ph?searchtype=author&query=Cackett%2C+E+M">E. M. Cackett</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=D%27Angelo%2C+C">C. D'Angelo</a>, <a href="/search/astro-ph?searchtype=author&query=Degenaar%2C+N">N. Degenaar</a>, <a href="/search/astro-ph?searchtype=author&query=Miller%2C+J+M">J. M. Miller</a>, <a href="/search/astro-ph?searchtype=author&query=Reynolds%2C+M">M. Reynolds</a>, <a href="/search/astro-ph?searchtype=author&query=Wijnands%2C+R">R. Wijnands</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="1310.5622v1-abstract-short" style="display: inline;"> We conducted the first long-term (60 days), multiwavelength (optical, ultraviolet, and X-ray) simultaneous monitoring of Cen X-4 with daily Swift observations, with the goal of understanding variability in the low mass X-ray binary Cen X-4 during quiescence. We found Cen X-4 to be highly variable in all energy bands on timescales from days to months, with the strongest quiescent variability a fact… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1310.5622v1-abstract-full').style.display = 'inline'; document.getElementById('1310.5622v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1310.5622v1-abstract-full" style="display: none;"> We conducted the first long-term (60 days), multiwavelength (optical, ultraviolet, and X-ray) simultaneous monitoring of Cen X-4 with daily Swift observations, with the goal of understanding variability in the low mass X-ray binary Cen X-4 during quiescence. We found Cen X-4 to be highly variable in all energy bands on timescales from days to months, with the strongest quiescent variability a factor of 22 drop in the X-ray count rate in only 4 days. The X-ray, UV and optical (V band) emission are correlated on timescales down to less than 110 s. The shape of the correlation is a power law with index gamma about 0.2-0.6. The X-ray spectrum is well fitted by a hydrogen NS atmosphere (kT=59-80 eV) and a power law (with spectral index Gamma=1.4-2.0), with the spectral shape remaining constant as the flux varies. Both components vary in tandem, with each responsible for about 50% of the total X-ray flux, implying that they are physically linked. We conclude that the X-rays are likely generated by matter accreting down to the NS surface. Moreover, based on the short timescale of the correlation, we also unambiguously demonstrate that the UV emission can not be due to either thermal emission from the stream impact point, or a standard optically thick, geometrically thin disc. The spectral energy distribution shows a small UV emitting region, too hot to arise from the accretion disk, that we identified as a hot spot on the companion star. Therefore, the UV emission is most likely produced by reprocessing from the companion star, indeed the vertical size of the disc is small and can only reprocess a marginal fraction of the X-ray emission. We also found the accretion disc in quiescence to likely be UV faint, with a minimal contribution to the whole UV flux. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1310.5622v1-abstract-full').style.display = 'none'; document.getElementById('1310.5622v1-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 October, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 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">5 pages, 4 figures, submitted to Proc. Int. Conf. Physics at the Magnetospheric Boundary, Geneva, Switzerland (25-28 June, 2013)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> 2013, MNRAS, 2427 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1307.2492">arXiv:1307.2492</a> <span> [<a href="https://arxiv.org/pdf/1307.2492">pdf</a>, <a href="https://arxiv.org/ps/1307.2492">ps</a>, <a href="https://arxiv.org/format/1307.2492">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/stt1741">10.1093/mnras/stt1741 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Daily, multiwavelength Swift monitoring of the neutron star low-mass X-ray binary Cen X-4: evidence for accretion and reprocessing during quiescence </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Bernardini%2C+F">F. Bernardini</a>, <a href="/search/astro-ph?searchtype=author&query=Cackett%2C+E+M">E. M. Cackett</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=D%27Angelo%2C+C">C. D'Angelo</a>, <a href="/search/astro-ph?searchtype=author&query=Degenaar%2C+N">N. Degenaar</a>, <a href="/search/astro-ph?searchtype=author&query=Miller%2C+J+M">J. M. Miller</a>, <a href="/search/astro-ph?searchtype=author&query=Reynolds%2C+M">M. Reynolds</a>, <a href="/search/astro-ph?searchtype=author&query=Wijnands%2C+R">R. Wijnands</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="1307.2492v3-abstract-short" style="display: inline;"> We conducted the first long-term (60 days), multiwavelength (optical, ultraviolet, and X-ray) simultaneous monitoring of Cen X-4 with daily Swift observations from June to August 2012, with the goal of understanding variability in the low mass X-ray binary Cen X-4 during quiescence. We found Cen X-4 to be highly variable in all energy bands on timescales from days to months, with the strongest qui… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1307.2492v3-abstract-full').style.display = 'inline'; document.getElementById('1307.2492v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1307.2492v3-abstract-full" style="display: none;"> We conducted the first long-term (60 days), multiwavelength (optical, ultraviolet, and X-ray) simultaneous monitoring of Cen X-4 with daily Swift observations from June to August 2012, with the goal of understanding variability in the low mass X-ray binary Cen X-4 during quiescence. We found Cen X-4 to be highly variable in all energy bands on timescales from days to months, with the strongest quiescent variability a factor of 22 drop in the X-ray count rate in only 4 days. The X-ray, UV and optical (V band) emission are correlated on timescales down to less than 110 s. The shape of the correlation is a power law with index gamma about 0.2-0.6. The X-ray spectrum is well fitted by a hydrogen NS atmosphere (kT=59-80 eV) and a power law (with spectral index Gamma=1.4-2.0), with the spectral shape remaining constant as the flux varies. Both components vary in tandem, with each responsible for about 50% of the total X-ray flux, implying that they are physically linked. We conclude that the X-rays are likely generated by matter accreting down to the NS surface. Moreover, based on the short timescale of the correlation, we also unambiguously demonstrate that the UV emission can not be due to either thermal emission from the stream impact point, or a standard optically thick, geometrically thin disc. The spectral energy distribution shows a small UV emitting region, too hot to arise from the accretion disk, that we identified as a hot spot on the companion star. Therefore, the UV emission is most likely produced by reprocessing from the companion star, indeed the vertical size of the disc is small and can only reprocess a marginal fraction of the X-ray emission. We also found the accretion disc in quiescence to likely be UV faint, with a minimal contribution to the whole UV flux. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1307.2492v3-abstract-full').style.display = 'none'; document.getElementById('1307.2492v3-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 September, 2013; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 9 July, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 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">19 pages, 6 figures, 4 tables</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1306.2345">arXiv:1306.2345</a> <span> [<a href="https://arxiv.org/pdf/1306.2345">pdf</a>, <a href="https://arxiv.org/ps/1306.2345">ps</a>, <a href="https://arxiv.org/format/1306.2345">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/775/1/48">10.1088/0004-637X/775/1/48 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Continued Neutron Star Crust Cooling of the 11 Hz X-Ray Pulsar in Terzan 5: A Challenge to Heating and Cooling Models? </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Degenaar%2C+N">N. Degenaar</a>, <a href="/search/astro-ph?searchtype=author&query=Wijnands%2C+R">R. Wijnands</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Altamirano%2C+D">D. Altamirano</a>, <a href="/search/astro-ph?searchtype=author&query=Cackett%2C+E+M">E. M. Cackett</a>, <a href="/search/astro-ph?searchtype=author&query=Fridriksson%2C+J">J. Fridriksson</a>, <a href="/search/astro-ph?searchtype=author&query=Homan%2C+J">J. Homan</a>, <a href="/search/astro-ph?searchtype=author&query=Heinke%2C+C+O">C. O. Heinke</a>, <a href="/search/astro-ph?searchtype=author&query=Miller%2C+J+M">J. M. Miller</a>, <a href="/search/astro-ph?searchtype=author&query=Pooley%2C+D">D. Pooley</a>, <a href="/search/astro-ph?searchtype=author&query=Sivakoff%2C+G+R">G. R. Sivakoff</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="1306.2345v2-abstract-short" style="display: inline;"> The transient neutron star low-mass X-ray binary and 11 Hz X-ray pulsar IGR J17480-2446 in the globular cluster Terzan 5 exhibited an 11-week accretion outburst in 2010. Chandra observations performed within five months after the end of the outburst revealed evidence that the crust of the neutron star became substantially heated during the accretion episode and was subsequently cooling in quiescen… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1306.2345v2-abstract-full').style.display = 'inline'; document.getElementById('1306.2345v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1306.2345v2-abstract-full" style="display: none;"> The transient neutron star low-mass X-ray binary and 11 Hz X-ray pulsar IGR J17480-2446 in the globular cluster Terzan 5 exhibited an 11-week accretion outburst in 2010. Chandra observations performed within five months after the end of the outburst revealed evidence that the crust of the neutron star became substantially heated during the accretion episode and was subsequently cooling in quiescence. This provides the rare opportunity to probe the structure and composition of the crust. Here, we report on new Chandra observations of Terzan 5 that extend the monitoring to ~2.2 yr into quiescence. We find that the thermal flux and neutron star temperature have continued to decrease, but remain significantly above the values that were measured before the 2010 accretion phase. This suggests that the crust has not thermally relaxed yet, and may continue to cool. Such behavior is difficult to explain within our current understanding of heating and cooling of transiently accreting neutron stars. Alternatively, the quiescent emission may have settled at a higher observed equilibrium level (for the same interior temperature), in which case the neutron star crust may have fully cooled. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1306.2345v2-abstract-full').style.display = 'none'; document.getElementById('1306.2345v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 August, 2013; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 10 June, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 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">Accepted to ApJ without revision. Updated references and fixed few typos to match published version. 7 pages, 3 figures, 3 tables</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1306.1776">arXiv:1306.1776</a> <span> [<a href="https://arxiv.org/pdf/1306.1776">pdf</a>, <a href="https://arxiv.org/ps/1306.1776">ps</a>, <a href="https://arxiv.org/format/1306.1776">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/774/2/131">10.1088/0004-637X/774/2/131 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A change in the quiescent X-ray spectrum of the neutron star low-mass X-ray binary MXB 1659-29 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Cackett%2C+E+M">E. M. Cackett</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Cumming%2C+A">A. Cumming</a>, <a href="/search/astro-ph?searchtype=author&query=Degenaar%2C+N">N. Degenaar</a>, <a href="/search/astro-ph?searchtype=author&query=Fridriksson%2C+J+K">J. K. Fridriksson</a>, <a href="/search/astro-ph?searchtype=author&query=Homan%2C+J">J. Homan</a>, <a href="/search/astro-ph?searchtype=author&query=Miller%2C+J+M">J. M. Miller</a>, <a href="/search/astro-ph?searchtype=author&query=Wijnands%2C+R">R. Wijnands</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="1306.1776v2-abstract-short" style="display: inline;"> The quasi-persistent neutron star low-mass X-ray binary MXB 1659-29 went into quiescence in 2001, and we have followed its quiescent X-ray evolution since. Observations over the first 4 years showed a rapid drop in flux and temperature of the neutron star atmosphere, interpreted as cooling of the neutron star crust which had been heated during the 2.5 year outburst. However, observations taken app… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1306.1776v2-abstract-full').style.display = 'inline'; document.getElementById('1306.1776v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1306.1776v2-abstract-full" style="display: none;"> The quasi-persistent neutron star low-mass X-ray binary MXB 1659-29 went into quiescence in 2001, and we have followed its quiescent X-ray evolution since. Observations over the first 4 years showed a rapid drop in flux and temperature of the neutron star atmosphere, interpreted as cooling of the neutron star crust which had been heated during the 2.5 year outburst. However, observations taken approximately 1400 and 2400 days into quiescence were consistent with each other, suggesting the crust had reached thermal equilibrium with the core. Here we present a new Chandra observation of MXB 1659-29 taken 11 years into quiescence and 4 years since the last Chandra observation. This new observation shows an unexpected factor of ~3 drop in count rate and change in spectral shape since the last observation, which cannot be explained simply by continued cooling. Two possible scenarios are that either the neutron star temperature has remained unchanged and there has been an increase in the column density, or, alternatively the neutron star temperature has dropped precipitously and the spectrum is now dominated by a power-law component. The first scenario may be possible given that MXB 1659-29 is a near edge-on system, and an increase in column density could be due to build-up of material in, and a thickening of, a truncated accretion disk during quiescence. But, a large change in disk height may not be plausible if standard accretion disk theory holds during quiescence. Alternatively, the disk may be precessing, leading to a higher column density during this latest observation. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1306.1776v2-abstract-full').style.display = 'none'; document.getElementById('1306.1776v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 5 July, 2013; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 7 June, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 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">6 pages, 4 figures, accepted for publication in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1304.4942">arXiv:1304.4942</a> <span> [<a href="https://arxiv.org/pdf/1304.4942">pdf</a>, <a href="https://arxiv.org/format/1304.4942">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="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/10.1088/0004-637X/787/2/149">10.1088/0004-637X/787/2/149 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> On Silicon Group Elements Ejected by Supernovae Type Ia </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=De%2C+S">Soma De</a>, <a href="/search/astro-ph?searchtype=author&query=Timmes%2C+F+X">F. X. Timmes</a>, <a href="/search/astro-ph?searchtype=author&query=Athanassiadou%2C+T">Themis Athanassiadou</a>, <a href="/search/astro-ph?searchtype=author&query=Chamulak%2C+D+A">David A. Chamulak</a>, <a href="/search/astro-ph?searchtype=author&query=Hawley%2C+W">Wendy Hawley</a>, <a href="/search/astro-ph?searchtype=author&query=Jack%2C+D">Dennis Jack</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Calder%2C+A+C">Alan C. Calder</a>, <a href="/search/astro-ph?searchtype=author&query=Townsley%2C+D+M">Dean M. Townsley</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="1304.4942v2-abstract-short" style="display: inline;"> There is compelling evidence that the peak brightness of a Type Ia supernova is affected by the electron fraction Ye at the time of the explosion. The electron fraction is set by the aboriginal composition of the white dwarf and the reactions that occur during the pre explosive convective burning. To date, determining the makeup of the white dwarf progenitor has relied on indirect proxies, such as… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1304.4942v2-abstract-full').style.display = 'inline'; document.getElementById('1304.4942v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1304.4942v2-abstract-full" style="display: none;"> There is compelling evidence that the peak brightness of a Type Ia supernova is affected by the electron fraction Ye at the time of the explosion. The electron fraction is set by the aboriginal composition of the white dwarf and the reactions that occur during the pre explosive convective burning. To date, determining the makeup of the white dwarf progenitor has relied on indirect proxies, such as the average metallicity of the host stellar population. In this paper, we present analytical calculations supporting the idea that the electron fraction of the progenitor systematically influences the nucleosynthesis of silicon group ejecta in Type Ia supernovae. In particular, we suggest the abundances generated in quasi nuclear statistical equilibrium are preserved during the subsequent freezeout. This allows one to potential recovery of Ye at explosion from the abundances recovered from an observed spectra. We show that measurement of 28Si, 32S, 40Ca, and 54Fe abundances can be used to construct Ye in the silicon rich regions of the supernovae. If these four abundances are determined exactly, they are sufficient to recover Ye to 6 percent. This is because these isotopes dominate the composition of silicon-rich material and iron rich material in quasi nuclear statistical equilibrium. Analytical analysis shows that the 28Si abundance is insensitive to Ye, the 32S abundance has a nearly linear trend with Ye, and the 40Ca abundance has a nearly quadratic trend with Ye. We verify these trends with post-processing of 1D models and show that these trends are reflected in model synthetic spectra. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1304.4942v2-abstract-full').style.display = 'none'; document.getElementById('1304.4942v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 8 May, 2014; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 17 April, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 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">Submitted to 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/1303.3270">arXiv:1303.3270</a> <span> [<a href="https://arxiv.org/pdf/1303.3270">pdf</a>, <a href="https://arxiv.org/format/1303.3270">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="Nuclear Theory">nucl-th</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/PhysRevC.90.025802">10.1103/PhysRevC.90.025802 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Magnetar giant flare oscillations and the nuclear symmetry energy </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Deibel%2C+A+T">Alex T. Deibel</a>, <a href="/search/astro-ph?searchtype=author&query=Steiner%2C+A+W">Andrew W. Steiner</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</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="1303.3270v2-abstract-short" style="display: inline;"> If the observed quasi-periodic oscillations in magnetar flares are partially confined to the crust, then the oscillation frequencies are unique probes of the nuclear physics of the neutron star crust. We study crustal oscillations in magnetars including corrections for a finite Alfven velocity. Our crust model uses a new nuclear mass formula that predicts nuclear masses with an accuracy very close… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1303.3270v2-abstract-full').style.display = 'inline'; document.getElementById('1303.3270v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1303.3270v2-abstract-full" style="display: none;"> If the observed quasi-periodic oscillations in magnetar flares are partially confined to the crust, then the oscillation frequencies are unique probes of the nuclear physics of the neutron star crust. We study crustal oscillations in magnetars including corrections for a finite Alfven velocity. Our crust model uses a new nuclear mass formula that predicts nuclear masses with an accuracy very close to that of the finite range droplet model. This mass model for equilibrium nuclei also includes shell corrections and an updated neutron-drip line. We perturb our crust model to predict axial crust modes and assign them to observed giant flare quasi-periodic oscillation frequencies from the soft gamma-ray repeater SGR 1806-20. We find magnetar crusts that match observations for various magnetic field strengths, entrainment of the free neutron gas in the inner crust, and crust-core transition densities. We find that observations can be reconciled with smaller values of the symmetry energy slope parameter, L, if there is a significant amount of entrainment of the neutrons by the superfluid or if the crust-core transition density is large. We also find neutron star masses and radii which are in agreement with expectations from what is known about low-density matter from nuclear experiment. Matching observations with a field-free model we obtain the approximate values of M =1.35 Msun and R = 11.9 km. Matching observations using a model with the surface dipole field of SGR 1806-20 (B=2.4x10^15 G) we obtain the approximate values of M = 1.25 Msun and R = 12.4 km. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1303.3270v2-abstract-full').style.display = 'none'; document.getElementById('1303.3270v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 August, 2014; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 13 March, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 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">10 pages, 7 figures. Accepted for publication in Phys. Rev. C</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> INT-PUB-13-011 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1301.0319">arXiv:1301.0319</a> <span> [<a href="https://arxiv.org/pdf/1301.0319">pdf</a>, <a href="https://arxiv.org/format/1301.0319">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="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/10.1088/0067-0049/208/1/4">10.1088/0067-0049/208/1/4 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Paxton%2C+B">Bill Paxton</a>, <a href="/search/astro-ph?searchtype=author&query=Cantiello%2C+M">Matteo Cantiello</a>, <a href="/search/astro-ph?searchtype=author&query=Arras%2C+P">Phil Arras</a>, <a href="/search/astro-ph?searchtype=author&query=Bildsten%2C+L">Lars Bildsten</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Dotter%2C+A">Aaron Dotter</a>, <a href="/search/astro-ph?searchtype=author&query=Mankovich%2C+C">Christopher Mankovich</a>, <a href="/search/astro-ph?searchtype=author&query=Montgomery%2C+M+H">M. H. Montgomery</a>, <a href="/search/astro-ph?searchtype=author&query=Stello%2C+D">Dennis Stello</a>, <a href="/search/astro-ph?searchtype=author&query=Timmes%2C+F+X">F. X. Timmes</a>, <a href="/search/astro-ph?searchtype=author&query=Townsend%2C+R">Richard Townsend</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="1301.0319v2-abstract-short" style="display: inline;"> We substantially update the capabilities of the open source software package Modules for Experiments in Stellar Astrophysics (MESA), and its one-dimensional stellar evolution module, MESA Star. Improvements in MESA Star's ability to model the evolution of giant planets now extends its applicability down to masses as low as one-tenth that of Jupiter. The dramatic improvement in asteroseismology ena… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1301.0319v2-abstract-full').style.display = 'inline'; document.getElementById('1301.0319v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1301.0319v2-abstract-full" style="display: none;"> We substantially update the capabilities of the open source software package Modules for Experiments in Stellar Astrophysics (MESA), and its one-dimensional stellar evolution module, MESA Star. Improvements in MESA Star's ability to model the evolution of giant planets now extends its applicability down to masses as low as one-tenth that of Jupiter. The dramatic improvement in asteroseismology enabled by the space-based Kepler and CoRoT missions motivates our full coupling of the ADIPLS adiabatic pulsation code with MESA Star. This also motivates a numerical recasting of the Ledoux criterion that is more easily implemented when many nuclei are present at non-negligible abundances. This impacts the way in which MESA Star calculates semi-convective and thermohaline mixing. We exhibit the evolution of 3-8 Msun stars through the end of core He burning, the onset of He thermal pulses, and arrival on the white dwarf cooling sequence. We implement diffusion of angular momentum and chemical abundances that enable calculations of rotating-star models, which we compare thoroughly with earlier work. We introduce a new treatment of radiation-dominated envelopes that allows the uninterrupted evolution of massive stars to core collapse. This enables the generation of new sets of supernovae, long gamma-ray burst, and pair-instability progenitor models. We substantially modify the way in which MESA Star solves the fully coupled stellar structure and composition equations, and we show how this has improved MESA's performance scaling on multi-core processors. Updates to the modules for equation of state, opacity, nuclear reaction rates, and atmospheric boundary conditions are also provided. We describe the MESA Software Development Kit (SDK) that packages all the required components needed to form a unified and maintained build environment for MESA. [Abridged] <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1301.0319v2-abstract-full').style.display = 'none'; document.getElementById('1301.0319v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 June, 2013; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 2 January, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 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">Accepted for publication in The ApJ Supplement Series. Extra informations required to reproduce the calculations in this paper are available at http://mesastar.org/results/mesa2</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1210.4510">arXiv:1210.4510</a> <span> [<a href="https://arxiv.org/pdf/1210.4510">pdf</a>, <a href="https://arxiv.org/ps/1210.4510">ps</a>, <a href="https://arxiv.org/format/1210.4510">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/stt804">10.1093/mnras/stt804 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> An X-ray-UV correlation in Cen X-4 during quiescence </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Cackett%2C+E+M">E. M. Cackett</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Degenaar%2C+N">N. Degenaar</a>, <a href="/search/astro-ph?searchtype=author&query=Miller%2C+J+M">J. M. Miller</a>, <a href="/search/astro-ph?searchtype=author&query=Reynolds%2C+M">M. Reynolds</a>, <a href="/search/astro-ph?searchtype=author&query=Wijnands%2C+R">R. Wijnands</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="1210.4510v2-abstract-short" style="display: inline;"> Quiescent emission from the neutron star low-mass X-ray binary Cen X-4 is seen to be variable on timescales from hundreds of seconds to years, suggesting that at least in this object, low-level accretion is important during quiescence. Here we present results from recent XMM-Newton and Swift observations of Cen X-4, where the X-ray flux (0.5 - 10 keV) varies by a factor of 6.5 between the brightes… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1210.4510v2-abstract-full').style.display = 'inline'; document.getElementById('1210.4510v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1210.4510v2-abstract-full" style="display: none;"> Quiescent emission from the neutron star low-mass X-ray binary Cen X-4 is seen to be variable on timescales from hundreds of seconds to years, suggesting that at least in this object, low-level accretion is important during quiescence. Here we present results from recent XMM-Newton and Swift observations of Cen X-4, where the X-ray flux (0.5 - 10 keV) varies by a factor of 6.5 between the brightest and faintest states. We find a positive correlation between the X-ray flux and the simultaneous near-UV flux, where as there is no significant correlation between the X-ray and simultaneous optical (V, B) fluxes. This suggests that while the X-ray and UV emitting regions are somehow linked, the optical region originates elsewhere. Comparing the luminosities, it is plausible that the UV emission originates due to reprocessing of the X-ray flux by the accretion disk, with the hot inner region of the disk being a possible location for the UV emitting region. The optical emission, however, could be dominated by the donor star. The X-ray/UV correlation does not favour the accretion stream-impact point as the source of the UV emission. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1210.4510v2-abstract-full').style.display = 'none'; document.getElementById('1210.4510v2-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 May, 2013; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 16 October, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 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">8 pages, 3 figures, accepted for publication in MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1208.1986">arXiv:1208.1986</a> <span> [<a href="https://arxiv.org/pdf/1208.1986">pdf</a>, <a href="https://arxiv.org/ps/1208.1986">ps</a>, <a href="https://arxiv.org/format/1208.1986">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="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/10.1088/0004-637X/757/2/175">10.1088/0004-637X/757/2/175 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Evaluating Systematic Dependencies of Type Ia Supernovae: The Influence of Central Density </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Krueger%2C+B+K">Brendan K. Krueger</a>, <a href="/search/astro-ph?searchtype=author&query=Jackson%2C+A+P">Aaron P. Jackson</a>, <a href="/search/astro-ph?searchtype=author&query=Calder%2C+A+C">Alan C. Calder</a>, <a href="/search/astro-ph?searchtype=author&query=Townsley%2C+D+M">Dean M. Townsley</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Timmes%2C+F+X">Francis X. Timmes</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="1208.1986v1-abstract-short" style="display: inline;"> We present a study exploring a systematic effect on the brightness of type Ia supernovae using numerical models that assume the single-degenerate paradigm. Our investigation varied the central density of the progenitor white dwarf at flame ignition, and considered its impact on the explosion yield, particularly the production and distribution of radioactive Ni-56, which powers the light curve. We… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1208.1986v1-abstract-full').style.display = 'inline'; document.getElementById('1208.1986v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1208.1986v1-abstract-full" style="display: none;"> We present a study exploring a systematic effect on the brightness of type Ia supernovae using numerical models that assume the single-degenerate paradigm. Our investigation varied the central density of the progenitor white dwarf at flame ignition, and considered its impact on the explosion yield, particularly the production and distribution of radioactive Ni-56, which powers the light curve. We performed a suite of two-dimensional simulations with randomized initial conditions, allowing us to characterize the statistical trends that we present. The simulations indicate that production of Fe-group material is statistically independent of progenitor central density, but the mass of stable Fe-group isotopes is tightly correlated with central density, with a decrease in the production of Ni-56 at higher central densities. These results imply progenitors with higher central densities produce dimmer events. We provide details of the post-explosion distribution of Ni-56 in the models, including the lack of a consistent centrally-located deficit of Ni-56, which may be compared to observed remnants. By performing a self-consistent extrapolation of our model yields and considering the main-sequence lifetime of the progenitor star and the elapsed time between the formation of the white dwarf and the onset of accretion, we develop a brightness-age relation that improves our prediction of the expected trend for single degenerates and we compare this relation with observations. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1208.1986v1-abstract-full').style.display = 'none'; document.getElementById('1208.1986v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 9 August, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 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">25 pages, 18 figures, accepted to ApJ on July 30, 2012</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophysical Journal 757 (2012) 175 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1205.6871">arXiv:1205.6871</a> <span> [<a href="https://arxiv.org/pdf/1205.6871">pdf</a>, <a href="https://arxiv.org/ps/1205.6871">ps</a>, <a href="https://arxiv.org/format/1205.6871">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Nuclear Theory">nucl-th</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/10.1088/2041-8205/765/1/L5">10.1088/2041-8205/765/1/L5 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Neutron Star Mass-Radius Relation and the Equation of State of Dense Matter </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Steiner%2C+A+W">Andrew W. Steiner</a>, <a href="/search/astro-ph?searchtype=author&query=Lattimer%2C+J+M">James M. Lattimer</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</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="1205.6871v1-abstract-short" style="display: inline;"> The equation of state (EOS) of dense matter has been a long-sought goal of nuclear physics. Equations of state generate unique mass versus radius (M-R) relations for neutron stars, the ultra-dense remnants of stellar evolution. In this work, we determine the neutron star mass-radius relation and, based on recent observations of both transiently accreting and bursting sources, we show that the radi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1205.6871v1-abstract-full').style.display = 'inline'; document.getElementById('1205.6871v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1205.6871v1-abstract-full" style="display: none;"> The equation of state (EOS) of dense matter has been a long-sought goal of nuclear physics. Equations of state generate unique mass versus radius (M-R) relations for neutron stars, the ultra-dense remnants of stellar evolution. In this work, we determine the neutron star mass-radius relation and, based on recent observations of both transiently accreting and bursting sources, we show that the radius of a 1.4 solar mass neutron star lies between 10.4 and 12.9 km, independent of assumptions about the composition of the core. We show, for the first time, that these constraints remain valid upon removal from our sample of the most extreme transient sources or of the entire set of bursting sources; our constraints also apply even if deconfined quark matter exists in the neutron star core. Our results significantly constrain the dense matter EOS and are, furthermore, consistent with constraints from both heavy-ion collisions and theoretical studies of neutron matter. We predict a relatively weak dependence of the symmetry energy on the density and a value for the neutron skin thickness of lead which is less than 0.20 fm, results that are testable in forthcoming experiments. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1205.6871v1-abstract-full').style.display = 'none'; document.getElementById('1205.6871v1-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 May, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2012. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> INT-PUB-12-028 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1205.0966">arXiv:1205.0966</a> <span> [<a href="https://arxiv.org/pdf/1205.0966">pdf</a>, <a href="https://arxiv.org/ps/1205.0966">ps</a>, <a href="https://arxiv.org/format/1205.0966">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1742-6596/402/1/012023">10.1088/1742-6596/402/1/012023 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> On Simulating Type Ia Supernovae </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Calder%2C+A+C">Alan C. Calder</a>, <a href="/search/astro-ph?searchtype=author&query=Krueger%2C+B+K">Brendan K. Krueger</a>, <a href="/search/astro-ph?searchtype=author&query=Jackson%2C+A+P">Aaron P. Jackson</a>, <a href="/search/astro-ph?searchtype=author&query=Townsley%2C+D+M">Dean M. Townsley</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Timmes%2C+F+X">Francis X. Timmes</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="1205.0966v1-abstract-short" style="display: inline;"> Type Ia supernovae are bright stellar explosions distinguished by standardizable light curves that allow for their use as distance indicators for cosmological studies. Despite their highly successful use in this capacity, the progenitors of these events are incompletely understood. We describe simulating type Ia supernovae in the paradigm of a thermonuclear runaway occurring in a massive white dwa… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1205.0966v1-abstract-full').style.display = 'inline'; document.getElementById('1205.0966v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1205.0966v1-abstract-full" style="display: none;"> Type Ia supernovae are bright stellar explosions distinguished by standardizable light curves that allow for their use as distance indicators for cosmological studies. Despite their highly successful use in this capacity, the progenitors of these events are incompletely understood. We describe simulating type Ia supernovae in the paradigm of a thermonuclear runaway occurring in a massive white dwarf star. We describe the multi-scale physical processes that realistic models must incorporate and the numerical models for these that we employ. In particular, we describe a flame-capturing scheme that addresses the problem of turbulent thermonuclear combustion on unresolved scales. We present the results of our study of the systematics of type Ia supernovae including trends in brightness following from properties of the host galaxy that agree with observations. We also present performance results from simulations on leadership-class architectures. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1205.0966v1-abstract-full').style.display = 'none'; document.getElementById('1205.0966v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 4 May, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 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">13 pages, 3 figures, accepted to proceedings of the Conference on Computational Physics, Oct. 30 - Nov. 3, 2011</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1112.2136">arXiv:1112.2136</a> <span> [<a href="https://arxiv.org/pdf/1112.2136">pdf</a>, <a href="https://arxiv.org/format/1112.2136">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Nuclear Theory">nucl-th</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="Nuclear Experiment">nucl-ex</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/PhysRevLett.109.141101">10.1103/PhysRevLett.109.141101 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Low-temperature triple-alpha rate in a full three-body model </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Nguyen%2C+N+B">N. B. Nguyen</a>, <a href="/search/astro-ph?searchtype=author&query=Nunes%2C+F+M">F. M. Nunes</a>, <a href="/search/astro-ph?searchtype=author&query=Thompson%2C+I+J">I. J. Thompson</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</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="1112.2136v2-abstract-short" style="display: inline;"> A new full three-body method is introduced to compute the rate of the triple-alpha capture reaction which is the primary source of $^{12}$C in stars. In this work, we combine the Faddeev hyperspherical harmonics and the R-matrix method to obtain a full solution to the three-body $伪+伪+伪$ continuum. Particular attention is paid to the long range effects caused by the pairwise Coulomb interactions. T… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1112.2136v2-abstract-full').style.display = 'inline'; document.getElementById('1112.2136v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1112.2136v2-abstract-full" style="display: none;"> A new full three-body method is introduced to compute the rate of the triple-alpha capture reaction which is the primary source of $^{12}$C in stars. In this work, we combine the Faddeev hyperspherical harmonics and the R-matrix method to obtain a full solution to the three-body $伪+伪+伪$ continuum. Particular attention is paid to the long range effects caused by the pairwise Coulomb interactions. The new rate agrees with the NACRE rate for temperatures greater than 0.07 GK, but a large enhancement at lower temperature is found ($\approx 10^{14}$ at 0.02 GK). Our results are compared to previous calculations where additional approximations were made. We show that the new rate does not significantly change the evolution of stars around one solar mass. In particular, such stars still undergo a red-giant phase consistent with observations, and no significant differences are found in the final white dwarfs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1112.2136v2-abstract-full').style.display = 'none'; document.getElementById('1112.2136v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 August, 2012; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 9 December, 2011; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 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">5pg, 2 figures, resubmitted</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1109.5200">arXiv:1109.5200</a> <span> [<a href="https://arxiv.org/pdf/1109.5200">pdf</a>, <a href="https://arxiv.org/ps/1109.5200">ps</a>, <a href="https://arxiv.org/format/1109.5200">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Nuclear Experiment">nucl-ex</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/10.1103/PhysRevLett.107.172503">10.1103/PhysRevLett.107.172503 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Time-of-flight mass measurements for nuclear processes in neutron star crusts </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Estrade%2C+A">A. Estrade</a>, <a href="/search/astro-ph?searchtype=author&query=Matos%2C+M">M. Matos</a>, <a href="/search/astro-ph?searchtype=author&query=Schatz%2C+H">H. Schatz</a>, <a href="/search/astro-ph?searchtype=author&query=Amthor%2C+A+M">A. M. Amthor</a>, <a href="/search/astro-ph?searchtype=author&query=Bazin%2C+D">D. Bazin</a>, <a href="/search/astro-ph?searchtype=author&query=Beard%2C+M">M. Beard</a>, <a href="/search/astro-ph?searchtype=author&query=Becerril%2C+A">A. Becerril</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Cyburt%2C+R">R. Cyburt</a>, <a href="/search/astro-ph?searchtype=author&query=Elliot%2C+T">T. Elliot</a>, <a href="/search/astro-ph?searchtype=author&query=Gade%2C+A">A. Gade</a>, <a href="/search/astro-ph?searchtype=author&query=Galaviz%2C+D">D. Galaviz</a>, <a href="/search/astro-ph?searchtype=author&query=George%2C+S">S. George</a>, <a href="/search/astro-ph?searchtype=author&query=Gupta%2C+S+S">S. S. Gupta</a>, <a href="/search/astro-ph?searchtype=author&query=Hix%2C+W+R">W. R. Hix</a>, <a href="/search/astro-ph?searchtype=author&query=Lau%2C+R">R. Lau</a>, <a href="/search/astro-ph?searchtype=author&query=Lorusso%2C+G">G. Lorusso</a>, <a href="/search/astro-ph?searchtype=author&query=Moller%2C+P">P. Moller</a>, <a href="/search/astro-ph?searchtype=author&query=Pereira%2C+J">J. Pereira</a>, <a href="/search/astro-ph?searchtype=author&query=Portillo%2C+M">M. Portillo</a>, <a href="/search/astro-ph?searchtype=author&query=Rogers%2C+A+M">A. M. Rogers</a>, <a href="/search/astro-ph?searchtype=author&query=Shapira%2C+D">D. Shapira</a>, <a href="/search/astro-ph?searchtype=author&query=Smith%2C+E">E. Smith</a>, <a href="/search/astro-ph?searchtype=author&query=Stolz%2C+A">A. Stolz</a>, <a href="/search/astro-ph?searchtype=author&query=Wallace%2C+M">M. Wallace</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="1109.5200v1-abstract-short" style="display: inline;"> The location of electron capture heat sources in the crust of accreting neutron stars depends on the masses of extremely neutron-rich nuclei. We present first results from a new implementation of the time-of-flight technique to measure nuclear masses of rare isotopes at the National Superconducting Cyclotron Laboratory. The masses of 16 neutron-rich nuclei in the scandium -- nickel range were dete… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1109.5200v1-abstract-full').style.display = 'inline'; document.getElementById('1109.5200v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1109.5200v1-abstract-full" style="display: none;"> The location of electron capture heat sources in the crust of accreting neutron stars depends on the masses of extremely neutron-rich nuclei. We present first results from a new implementation of the time-of-flight technique to measure nuclear masses of rare isotopes at the National Superconducting Cyclotron Laboratory. The masses of 16 neutron-rich nuclei in the scandium -- nickel range were determined simultaneously, improving the accuracy compared to previous data in 12 cases. The masses of $^{61}${V}, $^{63}${Cr}, $^{66}${Mn}, and $^{74}${Ni} were measured for the first time with mass excesses of $-30.510(890)$ MeV, $-35.280(650)$ MeV, $-36.900(790)$ MeV, and $-49.210(990)$ MeV, respectively. With the measurement of the $^{66}$Mn mass, the locations of the two dominant electron capture heat sources in the outer crust of accreting neutron stars that exhibit superbursts are now experimentally constrained. We find that the location of the $^{66}$Fe$\rightarrow^{66}$Mn electron capture transition occurs significantly closer to the surface than previously assumed because our new experimental Q-value is 2.1 MeV (2.6$蟽$) smaller than predicted by the FRDM mass model. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1109.5200v1-abstract-full').style.display = 'none'; document.getElementById('1109.5200v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 September, 2011; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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">4 pages, 3 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1107.5317">arXiv:1107.5317</a> <span> [<a href="https://arxiv.org/pdf/1107.5317">pdf</a>, <a href="https://arxiv.org/ps/1107.5317">ps</a>, <a href="https://arxiv.org/format/1107.5317">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/10.1111/j.1745-3933.2011.01164.x">10.1111/j.1745-3933.2011.01164.x <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Evidence for crust cooling in the transiently accreting 11-Hz X-ray pulsar in the globular cluster Terzan 5 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Degenaar%2C+N">N. Degenaar</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Wijnands%2C+R">R. Wijnands</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="1107.5317v2-abstract-short" style="display: inline;"> The temporal heating and subsequent cooling of the crusts of transiently accreting neutron stars carries unique information about their structure and a variety of nuclear reaction processes. We report on a new Chandra Director's Discretionary Time observation of the globular cluster Terzan 5, aimed to monitor the transiently accreting 11-Hz X-ray pulsar IGR J17480-2446 after the cessation of its r… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1107.5317v2-abstract-full').style.display = 'inline'; document.getElementById('1107.5317v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1107.5317v2-abstract-full" style="display: none;"> The temporal heating and subsequent cooling of the crusts of transiently accreting neutron stars carries unique information about their structure and a variety of nuclear reaction processes. We report on a new Chandra Director's Discretionary Time observation of the globular cluster Terzan 5, aimed to monitor the transiently accreting 11-Hz X-ray pulsar IGR J17480-2446 after the cessation of its recent 10-week long accretion outburst. During the observation, which was performed ~125 days into quiescence, the source displays a thermal spectrum that fits to a neutron star atmosphere model with a temperature for an observer at infinity of kT~92 eV. This is ~10% lower than found ~75 days earlier, yet ~20% higher than the quiescent base level measured prior to the recent outburst. This can be interpreted as cooling of the accretion-heated neutron star crust, and implies that crust cooling is observable after short accretion episodes. Comparison with neutron star thermal evolution simulations indicates that substantial heat must be released at shallow depth inside the neutron star, which is not accounted for in current nuclear heating models. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1107.5317v2-abstract-full').style.display = 'none'; document.getElementById('1107.5317v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 4 November, 2011; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 26 July, 2011; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 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">5 pages, 3 figures, 1 table. Minor changes according to referee report. MNRAS Letters in press</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1104.3864">arXiv:1104.3864</a> <span> [<a href="https://arxiv.org/pdf/1104.3864">pdf</a>, <a href="https://arxiv.org/ps/1104.3864">ps</a>, <a href="https://arxiv.org/format/1104.3864">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/0004-637X/738/2/129">10.1088/0004-637X/738/2/129 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Discovery of a candidate quiescent low-mass X-ray binary in the globular cluster NGC 6553 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Guillot%2C+S">Sebastien Guillot</a>, <a href="/search/astro-ph?searchtype=author&query=Rutledge%2C+R+E">Robert E. Rutledge</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Pavlov%2C+G+G">George G. Pavlov</a>, <a href="/search/astro-ph?searchtype=author&query=Zavlin%2C+V+E">Vyacheslav E. Zavlin</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="1104.3864v2-abstract-short" style="display: inline;"> This paper reports the search for quiescent low-mass X-ray binaries (qLMXBs) in the globular cluster (GC) NGC 6553 using an XMM-Newton observation designed specifically for that purpose. We spectrally identify one candidate qLMXB in the core of the cluster, based on the consistency of the spectrum with a neutron star H-atmosphere model at the distance of NGC 6553. Specifically, the best-fit radius… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1104.3864v2-abstract-full').style.display = 'inline'; document.getElementById('1104.3864v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1104.3864v2-abstract-full" style="display: none;"> This paper reports the search for quiescent low-mass X-ray binaries (qLMXBs) in the globular cluster (GC) NGC 6553 using an XMM-Newton observation designed specifically for that purpose. We spectrally identify one candidate qLMXB in the core of the cluster, based on the consistency of the spectrum with a neutron star H-atmosphere model at the distance of NGC 6553. Specifically, the best-fit radius found using the three XMM European Photon Imaging Camera spectra is R_NS=6.3(+2.3)(-0.8) km (for M_NS=1.4 Msun) and the best-fit temperature is kTeff=136 (+21)(-34) eV. Both physical parameters are in accordance with typical values of previously identified qLMXBs in GC and in the field, i.e., R_NS~5-20 km and kTeff~50-150 eV. A power-law (PL) component with a photon index Gamma=2.1(+0.5)(-0.8) is also required for the spectral fit and contributes to ~33% of the total flux of the X-ray source. A detailed analysis supports the hypothesis that the PL component originates from nearby sources in the core, unresolved with XMM. The analysis of an archived Chandra observation provides marginal additional support to the stated hypothesis. Finally, a catalog of all the sources detected within the XMM field of view is presented here. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1104.3864v2-abstract-full').style.display = 'none'; document.getElementById('1104.3864v2-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 July, 2011; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 19 April, 2011; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 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">10 pages, 5 figures, 3 tables. Accepted to ApJ (to be published in August 2011)</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1101.0081">arXiv:1101.0081</a> <span> [<a href="https://arxiv.org/pdf/1101.0081">pdf</a>, <a href="https://arxiv.org/ps/1101.0081">ps</a>, <a href="https://arxiv.org/format/1101.0081">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/736/2/162">10.1088/0004-637X/736/2/162 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Variable Quiescent X-ray Emission of the Neutron Star Transient XTE J1701-462 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Fridriksson%2C+J+K">Joel K. Fridriksson</a>, <a href="/search/astro-ph?searchtype=author&query=Homan%2C+J">Jeroen Homan</a>, <a href="/search/astro-ph?searchtype=author&query=Wijnands%2C+R">Rudy Wijnands</a>, <a href="/search/astro-ph?searchtype=author&query=Cackett%2C+E+M">Edward M. Cackett</a>, <a href="/search/astro-ph?searchtype=author&query=Altamirano%2C+D">Diego Altamirano</a>, <a href="/search/astro-ph?searchtype=author&query=Degenaar%2C+N">Nathalie Degenaar</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Mendez%2C+M">Mariano Mendez</a>, <a href="/search/astro-ph?searchtype=author&query=Belloni%2C+T+M">Tomaso M. Belloni</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="1101.0081v2-abstract-short" style="display: inline;"> We present the results of continued monitoring of the quiescent neutron star low-mass X-ray binary XTE J1701-462 with Chandra and Swift. A new Chandra observation from 2010 October extends our tracking of the neutron star surface temperature from ~800 days to ~1160 days since the end of an exceptionally luminous 19 month outburst. This observation indicates that the neutron star crust may still be… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1101.0081v2-abstract-full').style.display = 'inline'; document.getElementById('1101.0081v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1101.0081v2-abstract-full" style="display: none;"> We present the results of continued monitoring of the quiescent neutron star low-mass X-ray binary XTE J1701-462 with Chandra and Swift. A new Chandra observation from 2010 October extends our tracking of the neutron star surface temperature from ~800 days to ~1160 days since the end of an exceptionally luminous 19 month outburst. This observation indicates that the neutron star crust may still be slowly cooling toward thermal equilibrium with the core; another observation further into quiescence is needed to verify this. The shape of the overall cooling curve is consistent with that of a broken power law, although an exponential decay to a constant level cannot be excluded with the present data. To investigate possible low-level activity, we conducted a monitoring campaign of XTE J1701-462 with Swift during 2010 April-October. Short-term flares - presumably arising from episodic low-level accretion - were observed up to a luminosity of ~1e35 erg/s, ~20 times higher than the normal quiescent level. We conclude that flares of this magnitude are not likely to have significantly affected the equilibrium temperature of the neutron star and are probably not able to have a measurable impact on the cooling curve. However, it is possible that brighter and longer periods of low-level activity have had an appreciable effect on the equilibrium temperature. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1101.0081v2-abstract-full').style.display = 'none'; document.getElementById('1101.0081v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 August, 2011; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 30 December, 2010; <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">14 pages, 4 figures - matches published version except for a slight difference in the title due to an ApJ proofreader's mistake</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophys.J. 736 (2011) 162 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1011.4022">arXiv:1011.4022</a> <span> [<a href="https://arxiv.org/pdf/1011.4022">pdf</a>, <a href="https://arxiv.org/ps/1011.4022">ps</a>, <a href="https://arxiv.org/format/1011.4022">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> Evaluating Systematic Dependencies of Type Ia Supernovae </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Calder%2C+A+C">Alan C. Calder</a>, <a href="/search/astro-ph?searchtype=author&query=Krueger%2C+B+K">Brendan K. Krueger</a>, <a href="/search/astro-ph?searchtype=author&query=Jackson%2C+A+P">Aaron P. Jackson</a>, <a href="/search/astro-ph?searchtype=author&query=Townsley%2C+D+M">Dean M. Townsley</a>, <a href="/search/astro-ph?searchtype=author&query=Timmes%2C+F+X">Francis X. Timmes</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Chamulak%2C+D+A">David A. Chamulak</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="1011.4022v1-abstract-short" style="display: inline;"> Type Ia supernovae are bright stellar explosions thought to occur when a thermonuclear runaway consumes roughly a solar mass of degenerate stellar material. These events produce and disseminate iron-peak elements, and properties of their light curves allow for standardization and subsequent use as cosmological distance indicators. The explosion mechanism of these events remains, however, only part… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1011.4022v1-abstract-full').style.display = 'inline'; document.getElementById('1011.4022v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1011.4022v1-abstract-full" style="display: none;"> Type Ia supernovae are bright stellar explosions thought to occur when a thermonuclear runaway consumes roughly a solar mass of degenerate stellar material. These events produce and disseminate iron-peak elements, and properties of their light curves allow for standardization and subsequent use as cosmological distance indicators. The explosion mechanism of these events remains, however, only partially understood. Many models posit the explosion beginning with a deflagration born near the center of a white dwarf that has gained mass from a stellar companion. In order to match observations, models of this single-degenerate scenario typically invoke a subsequent transition of the (subsonic) deflagration to a (supersonic) detonation that rapidly consumes the star. We present an investigation into the systematics of thermonuclear supernovae assuming this paradigm. We utilize a statistical framework for a controlled study of two-dimensional simulations of these events from randomized initial conditions. We investigate the effect of the composition and thermal history of the progenitor on the radioactive yield, and thus brightness, of an event. Our results offer an explanation for some observed trends of mean brightness with properties of the host galaxy. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1011.4022v1-abstract-full').style.display = 'none'; document.getElementById('1011.4022v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 17 November, 2010; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 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">14 pages, to appear in the Proceedings of the SciDAC 2010 meeting</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1008.4727">arXiv:1008.4727</a> <span> [<a href="https://arxiv.org/pdf/1008.4727">pdf</a>, <a href="https://arxiv.org/ps/1008.4727">ps</a>, <a href="https://arxiv.org/format/1008.4727">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/2041-8205/722/2/L137">10.1088/2041-8205/722/2/L137 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Continued cooling of the crust in the neutron star low-mass X-ray binary KS 1731-260 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Cackett%2C+E+M">Edward M. Cackett</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Cumming%2C+A">Andrew Cumming</a>, <a href="/search/astro-ph?searchtype=author&query=Degenaar%2C+N">Nathalie Degenaar</a>, <a href="/search/astro-ph?searchtype=author&query=Miller%2C+J+M">Jon M. Miller</a>, <a href="/search/astro-ph?searchtype=author&query=Wijnands%2C+R">Rudy Wijnands</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="1008.4727v2-abstract-short" style="display: inline;"> Some neutron star low-mass X-ray binaries have very long outbursts (lasting several years) which can generate a significant amount of heat in the neutron star crust. After the system has returned to quiescence, the crust then thermally relaxes. This provides a rare opportunity to study the thermal properties of neutron star crusts, putting constraints on the thermal conductivity and hence the stru… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1008.4727v2-abstract-full').style.display = 'inline'; document.getElementById('1008.4727v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1008.4727v2-abstract-full" style="display: none;"> Some neutron star low-mass X-ray binaries have very long outbursts (lasting several years) which can generate a significant amount of heat in the neutron star crust. After the system has returned to quiescence, the crust then thermally relaxes. This provides a rare opportunity to study the thermal properties of neutron star crusts, putting constraints on the thermal conductivity and hence the structure and composition of the crust. KS 1731-260 is one of only four systems where this crustal cooling has been observed. Here, we present a new Chandra observation of this source approximately 8 years after the end of the last outburst, and 4 years since the last observation. We find that the source has continued to cool, with the cooling curve displaying a simple power-law decay. This suggests that the crust has not fully thermally relaxed yet, and may continue to cool further. A simple power law decay is in contrast to theoretical cooling models of the crust, which predict that the crust should now have cooled to the same temperature as the neutron star core. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1008.4727v2-abstract-full').style.display = 'none'; document.getElementById('1008.4727v2-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 September, 2010; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 27 August, 2010; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 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">Accepted to ApJ 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/1007.2823">arXiv:1007.2823</a> <span> [<a href="https://arxiv.org/pdf/1007.2823">pdf</a>, <a href="https://arxiv.org/ps/1007.2823">ps</a>, <a href="https://arxiv.org/format/1007.2823">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/720/2/1325">10.1088/0004-637X/720/2/1325 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Quiescent X-ray emission from Cen X-4: a variable thermal component </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Cackett%2C+E+M">Edward M. Cackett</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Miller%2C+J+M">Jon M. Miller</a>, <a href="/search/astro-ph?searchtype=author&query=Wijnands%2C+R">Rudy Wijnands</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="1007.2823v1-abstract-short" style="display: inline;"> The nearby neutron star low-mass X-ray binary, Cen X-4, has been in a quiescent state since its last outburst in 1979. Typically, quiescent emission from these objects consists of thermal emission (presumably from the neutron star surface) with an additional hard power-law tail of unknown nature. Variability has been observed during quiescence in Cen X-4 on both timescales as short as hundreds of… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1007.2823v1-abstract-full').style.display = 'inline'; document.getElementById('1007.2823v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1007.2823v1-abstract-full" style="display: none;"> The nearby neutron star low-mass X-ray binary, Cen X-4, has been in a quiescent state since its last outburst in 1979. Typically, quiescent emission from these objects consists of thermal emission (presumably from the neutron star surface) with an additional hard power-law tail of unknown nature. Variability has been observed during quiescence in Cen X-4 on both timescales as short as hundreds of seconds and as long as years. However, the nature of this variability is still unknown. Early observations seemed to show it was all due to a variable hard X-ray tail. Here, we present new and archival observations that contradict this. The most recent Suzaku observation of Cen X-4 finds it in a historically low state, a factor of 4.4 fainter than the brightest quiescent observation. As the spectrum during the brightest observation was comprised of approximately 60% from the thermal component and 40% from the power-law component, such a large change cannot be explained by just power-law variability. Spectral fits with a variable thermal component fit the data well, while spectral fits allowing both the column density and the power-law to vary do not, leading to the conclusion that the thermal component must be variable. Interestingly, we also find that the thermal fraction remains consistent between all epochs, implying that the thermal and power-law fluxes vary by approximately the same amount. If the emitting area remains unchanged between observations, then the effective surface temperature must change. Alternatively, if the temperature remains constant, then the emitting area must change. The nature of this thermal variability is unclear, but may be explained by variable low-level accretion. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1007.2823v1-abstract-full').style.display = 'none'; document.getElementById('1007.2823v1-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 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">8 pages, accepted for publication in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1007.2415">arXiv:1007.2415</a> <span> [<a href="https://arxiv.org/pdf/1007.2415">pdf</a>, <a href="https://arxiv.org/ps/1007.2415">ps</a>, <a href="https://arxiv.org/format/1007.2415">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/0004-637X/732/2/88">10.1088/0004-637X/732/2/88 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Neutron Star Radius Measurement with the Quiescent Low-Mass X-ray Binary U24 in NGC 6397 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Guillot%2C+S">Sebastien Guillot</a>, <a href="/search/astro-ph?searchtype=author&query=Rutledge%2C+R+E">Robert E. Rutledge</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</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="1007.2415v2-abstract-short" style="display: inline;"> This paper reports the spectral and timing analyses of the quiescent low-mass X-ray binary U24 observed during five archived Chandra-ACIS exposures of the nearby globular cluster NGC 6397, for a total of 350 ksec. We find that the X-ray flux and the parameters of the hydrogen atmosphere spectral model are consistent with those previously published for this source. On short timescales, we find no e… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1007.2415v2-abstract-full').style.display = 'inline'; document.getElementById('1007.2415v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1007.2415v2-abstract-full" style="display: none;"> This paper reports the spectral and timing analyses of the quiescent low-mass X-ray binary U24 observed during five archived Chandra-ACIS exposures of the nearby globular cluster NGC 6397, for a total of 350 ksec. We find that the X-ray flux and the parameters of the hydrogen atmosphere spectral model are consistent with those previously published for this source. On short timescales, we find no evidence of aperiodic intensity variability, with 90% confidence upper limits during five observations ranging between <8.6% rms and <19% rms, in the 0.0001-0.1 Hz frequency range (0.5-8.0 keV); and no evidence of periodic variability, with maximum observed powers in this frequency range having a chance probability of occurrence from a Poisson-deviated light curve in excess of 10%. We also report the improved neutron star physical radius measurements, with statistical accuracy of the order of ~10%: R_ns = 8.9(+0.9)(-0.6) km for M_ns = 1.4 Msun. Alternatively, we provide the confidence regions in mass-radius space as well as the best-fit projected radius R_infinity= 11.9(+1.0)(-0.8)km, as seen by an observer at infinity. The best-fit effective temperature, kTeff = 80(+4)(-5) eV, is used to estimate the neutron star core temperature which falls in the range T_core = (3.0 - 9.8) x10 7 K, depending on the atmosphere model considered. This makes U24 the third most precisely measured neutron star radius among qLMXBs, after those in OmCen and in M13. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1007.2415v2-abstract-full').style.display = 'none'; document.getElementById('1007.2415v2-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 March, 2011; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 14 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">Re-submission of version accepted to ApJ. The confidence region in mass-radius space has been added</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1007.1138">arXiv:1007.1138</a> <span> [<a href="https://arxiv.org/pdf/1007.1138">pdf</a>, <a href="https://arxiv.org/ps/1007.1138">ps</a>, <a href="https://arxiv.org/format/1007.1138">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="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/10.1088/0004-637X/720/1/99">10.1088/0004-637X/720/1/99 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Evaluating Systematic Dependencies of Type Ia Supernovae: The Influence of Deflagration to Detonation Density </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Jackson%2C+A+P">Aaron P. Jackson</a>, <a href="/search/astro-ph?searchtype=author&query=Calder%2C+A+C">Alan C. Calder</a>, <a href="/search/astro-ph?searchtype=author&query=Townsley%2C+D+M">Dean M. Townsley</a>, <a href="/search/astro-ph?searchtype=author&query=Chamulak%2C+D+A">David A. Chamulak</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Timmes%2C+F+X">F. X. Timmes</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="1007.1138v1-abstract-short" style="display: inline;"> We explore the effects of the deflagration to detonation transition (DDT) density on the production of Ni-56 in thermonuclear supernova explosions (type Ia supernovae). Within the DDT paradigm, the transition density sets the amount of expansion during the deflagration phase of the explosion and therefore the amount of nuclear statistical equilibrium (NSE) material produced. We employ a theoretica… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1007.1138v1-abstract-full').style.display = 'inline'; document.getElementById('1007.1138v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1007.1138v1-abstract-full" style="display: none;"> We explore the effects of the deflagration to detonation transition (DDT) density on the production of Ni-56 in thermonuclear supernova explosions (type Ia supernovae). Within the DDT paradigm, the transition density sets the amount of expansion during the deflagration phase of the explosion and therefore the amount of nuclear statistical equilibrium (NSE) material produced. We employ a theoretical framework for a well-controlled statistical study of two-dimensional simulations of thermonuclear supernovae with randomized initial conditions that can, with a particular choice of transition density, produce a similar average and range of Ni-56 masses to those inferred from observations. Within this framework, we utilize a more realistic "simmered" white dwarf progenitor model with a flame model and energetics scheme to calculate the amount of Ni-56 and NSE material synthesized for a suite of simulated explosions in which the transition density is varied in the range 1-3x10^7 g/cc. We find a quadratic dependence of the NSE yield on the log of the transition density, which is determined by the competition between plume rise and stellar expansion. By considering the effect of metallicity on the transition density, we find the NSE yield decreases by 0.055 +/- 0.004 solar masses for a 1 solar metallicity increase evaluated about solar metallicity. For the same change in metallicity, this result translates to a 0.067 +/- 0.004 solar mass decrease in the Ni-56 yield, slightly stronger than that due to the variation in electron fraction from the initial composition. Observations testing the dependence of the yield on metallicity remain somewhat ambiguous, but the dependence we find is comparable to that inferred from some studies. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1007.1138v1-abstract-full').style.display = 'none'; document.getElementById('1007.1138v1-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 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">15 pages, 13 figures, accepted to ApJ on July 6, 2010</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophys.J. 720 (2010) 99-113 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1007.0910">arXiv:1007.0910</a> <span> [<a href="https://arxiv.org/pdf/1007.0910">pdf</a>, <a href="https://arxiv.org/ps/1007.0910">ps</a>, <a href="https://arxiv.org/format/1007.0910">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/2041-8205/719/1/L5">10.1088/2041-8205/719/1/L5 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> On variations of the brightness of type Ia supernovae with the age of the host stellar population </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Krueger%2C+B+K">Brendan K. Krueger</a>, <a href="/search/astro-ph?searchtype=author&query=Jackson%2C+A+P">Aaron P. Jackson</a>, <a href="/search/astro-ph?searchtype=author&query=Townsley%2C+D+M">Dean M. Townsley</a>, <a href="/search/astro-ph?searchtype=author&query=Calder%2C+A+C">Alan C. Calder</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">Edward F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Timmes%2C+F+X">F. X. Timmes</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="1007.0910v1-abstract-short" style="display: inline;"> Recent observational studies of type Ia supernovae (SNeIa) suggest correlations between the peak brightness of an event and the age of the progenitor stellar population. This trend likely follows from properties of the progenitor white dwarf (WD), such as central density, that follow from properties of the host stellar population. We present a statistically well-controlled, systematic study utiliz… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1007.0910v1-abstract-full').style.display = 'inline'; document.getElementById('1007.0910v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1007.0910v1-abstract-full" style="display: none;"> Recent observational studies of type Ia supernovae (SNeIa) suggest correlations between the peak brightness of an event and the age of the progenitor stellar population. This trend likely follows from properties of the progenitor white dwarf (WD), such as central density, that follow from properties of the host stellar population. We present a statistically well-controlled, systematic study utilizing a suite of multi-dimensional SNeIa simulations investigating the influence of central density of the progenitor WD on the production of Fe-group material, particularly radioactive Ni-56, which powers the light curve. We find that on average, as the progenitor's central density increases, production of Fe-group material does not change but production of Ni-56 decreases. We attribute this result to a higher rate of neutronization at higher density. The central density of the progenitor is determined by the mass of the WD and the cooling time prior to the onset of mass transfer from the companion, as well as the subsequent accretion heating and neutrino losses. The dependence of this density on cooling time, combined with the result of our central density study, offers an explanation for the observed age-luminosity correlation: a longer cooling time raises the central density at ignition thereby producing less Ni-56 and thus a dimmer event. While our ensemble of results demonstrates a significant trend, we find considerable variation between realizations, indicating the necessity for averaging over an ensemble of simulations to demonstrate a statistically significant result. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1007.0910v1-abstract-full').style.display = 'none'; document.getElementById('1007.0910v1-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 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">5 pages, 4 figures, 1 table, accepted to ApJL</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophysical Journal Letters 719 (2010) L5-L9 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1007.0247">arXiv:1007.0247</a> <span> [<a href="https://arxiv.org/pdf/1007.0247">pdf</a>, <a href="https://arxiv.org/ps/1007.0247">ps</a>, <a href="https://arxiv.org/format/1007.0247">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div 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/10.1111/j.1365-2966.2010.17562.x">10.1111/j.1365-2966.2010.17562.x <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Further X-ray observations of EXO 0748-676 in quiescence: evidence for a cooling neutron star crust </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Degenaar%2C+N">N. Degenaar</a>, <a href="/search/astro-ph?searchtype=author&query=Wolff%2C+M+T">M. T. Wolff</a>, <a href="/search/astro-ph?searchtype=author&query=Ray%2C+P+S">P. S. Ray</a>, <a href="/search/astro-ph?searchtype=author&query=Wood%2C+K+S">K. S. Wood</a>, <a href="/search/astro-ph?searchtype=author&query=Homan%2C+J">J. Homan</a>, <a href="/search/astro-ph?searchtype=author&query=Lewin%2C+W+H+G">W. H. G. Lewin</a>, <a href="/search/astro-ph?searchtype=author&query=Jonker%2C+P+G">P. G. Jonker</a>, <a href="/search/astro-ph?searchtype=author&query=Cackett%2C+E+M">E. M. Cackett</a>, <a href="/search/astro-ph?searchtype=author&query=Miller%2C+J+M">J. M. Miller</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+E+F">E. F. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Wijnands%2C+R">R. Wijnands</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="1007.0247v2-abstract-short" style="display: inline;"> In late 2008, the quasi-persistent neutron star X-ray transient and eclipsing binary EXO 0748-676 started a transition from outburst to quiescence, after it had been actively accreting for more than 24 years. In a previous work, we discussed Chandra and Swift observations obtained during the first five months after this transition. Here, we report on further X-ray observations of EXO 0748-676, ext… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1007.0247v2-abstract-full').style.display = 'inline'; document.getElementById('1007.0247v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1007.0247v2-abstract-full" style="display: none;"> In late 2008, the quasi-persistent neutron star X-ray transient and eclipsing binary EXO 0748-676 started a transition from outburst to quiescence, after it had been actively accreting for more than 24 years. In a previous work, we discussed Chandra and Swift observations obtained during the first five months after this transition. Here, we report on further X-ray observations of EXO 0748-676, extending the quiescent monitoring to 1.6 years. Chandra and XMM-Newton data reveal quiescent X-ray spectra composed of a soft, thermal component that is well-fitted by a neutron star atmosphere model. An additional hard powerlaw tail is detected that changes non-monotonically over time, contributing between 4 and 20 percent to the total unabsorbed 0.5-10 keV flux. The combined set of Chandra, XMM-Newton and Swift data reveals that the thermal bolometric luminosity fades from ~1E34 to 6E33 (D/7.4 kpc)^2 erg/s, whereas the inferred neutron star effective temperature decreases from ~124 to 109 eV. We interpret the observed decay as cooling of the neutron star crust and show that the fractional quiescent temperature change of EXO 0748-676 is markedly smaller than observed for three other neutron star X-ray binaries that underwent prolonged accretion outbursts. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1007.0247v2-abstract-full').style.display = 'none'; document.getElementById('1007.0247v2-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 October, 2010; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 1 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">Moderate textual revisions according to referee report, accepted for publication in MNRAS</span> </p> </li> </ol> <nav class="pagination is-small is-centered breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" class="pagination-previous is-invisible">Previous </a> <a href="/search/?searchtype=author&query=Brown%2C+E+F&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Brown%2C+E+F&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Brown%2C+E+F&start=50" class="pagination-link " aria-label="Page 2" aria-current="page">2 </a> </li> </ul> </nav> <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 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