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</div> <div class="control"> <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=Richer%2C+H+B&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Richer%2C+H+B&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Richer%2C+H+B&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/2310.11800">arXiv:2310.11800</a> <span> [<a href="https://arxiv.org/pdf/2310.11800">pdf</a>, <a href="https://arxiv.org/format/2310.11800">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> Exploring the Chemistry and Mass Function of the Globular Cluster 47 Tucanae with New Theoretical Color-Magnitude Diagrams </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Gerasimov%2C+R">Roman Gerasimov</a>, <a href="/search/astro-ph?searchtype=author&query=Burgasser%2C+A+J">Adam J. Burgasser</a>, <a href="/search/astro-ph?searchtype=author&query=Caiazzo%2C+I">Ilaria Caiazzo</a>, <a href="/search/astro-ph?searchtype=author&query=Homeier%2C+D">Derek Homeier</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Correnti%2C+M">Matteo Correnti</a>, <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</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="2310.11800v1-abstract-short" style="display: inline;"> Despite their shared origin, members of globular clusters display star-to-star variations in composition. The observed pattern of element abundances is unique to these stellar environments, and cannot be fully explained by any proposed mechanism. It remains unclear whether stars form with chemical heterogeneity, or inherit it from interactions with other members. These scenarios may be differentia… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.11800v1-abstract-full').style.display = 'inline'; document.getElementById('2310.11800v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2310.11800v1-abstract-full" style="display: none;"> Despite their shared origin, members of globular clusters display star-to-star variations in composition. The observed pattern of element abundances is unique to these stellar environments, and cannot be fully explained by any proposed mechanism. It remains unclear whether stars form with chemical heterogeneity, or inherit it from interactions with other members. These scenarios may be differentiated by the dependence of chemical spread on stellar mass; however, obtaining a sufficiently large mass baseline requires abundance measurements on the lower main sequence that is too faint for spectroscopy even in the nearest globular clusters. We developed a stellar modelling method to obtain precise chemical abundances for stars near the end of the main sequence from multiband photometry, and applied it to the globular cluster 47 Tucanae. The computational efficiency is attained by matching chemical elements to the model components that are most sensitive to their abundance. We determined [O/Fe] for ~5000 members below the main sequence knee at the level of accuracy, comparable to the spectroscopic measurements of evolved members in literature. The inferred distribution disfavors stellar interactions as the origin of chemical spread; however, an accurate theory of accretion is required to draw a more definitive conclusion. We anticipate that future observations of 47 Tucanae with JWST will extend the mass baseline of our analysis into the substellar regime. Therefore, we present predicted color-magnitude diagrams and mass-magnitude relations for the brown dwarf members of 47 Tucanae. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.11800v1-abstract-full').style.display = 'none'; document.getElementById('2310.11800v1-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 October, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2023. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2310.03204">arXiv:2310.03204</a> <span> [<a href="https://arxiv.org/pdf/2310.03204">pdf</a>, <a href="https://arxiv.org/format/2310.03204">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> An Extremely Massive White Dwarf Escaped From the Hyades Star Cluster </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Miller%2C+D+R">David R. Miller</a>, <a href="/search/astro-ph?searchtype=author&query=Caiazzo%2C+I">Ilaria Caiazzo</a>, <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=El-Badry%2C+K">Kareem El-Badry</a>, <a href="/search/astro-ph?searchtype=author&query=Rodriguez%2C+A+C">Antonio C. Rodriguez</a>, <a href="/search/astro-ph?searchtype=author&query=Vanderbosch%2C+Z+P">Zachary P. Vanderbosch</a>, <a href="/search/astro-ph?searchtype=author&query=van+Roestel%2C+J">Jan van Roestel</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="2310.03204v1-abstract-short" style="display: inline;"> We searched the Gaia DR3 database for ultramassive white dwarfs with kinematics consistent with having escaped the nearby Hyades open cluster, identifying three such candidates. Two of these candidates have masses estimated from Gaia photometry of approximately 1.1 solar masses; their status as products of single stellar evolution that have escaped the cluster was deemed too questionable for immed… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.03204v1-abstract-full').style.display = 'inline'; document.getElementById('2310.03204v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2310.03204v1-abstract-full" style="display: none;"> We searched the Gaia DR3 database for ultramassive white dwarfs with kinematics consistent with having escaped the nearby Hyades open cluster, identifying three such candidates. Two of these candidates have masses estimated from Gaia photometry of approximately 1.1 solar masses; their status as products of single stellar evolution that have escaped the cluster was deemed too questionable for immediate follow-up analysis. The remaining candidate has an expected mass >1.3 solar masses, significantly reducing the probability of it being an interloper. Analysis of follow-up Gemini GMOS spectroscopy for this source reveals a non-magnetized hydrogen atmosphere white dwarf with a mass and age consistent with having formed from a single star. Assuming a single-stellar evolution formation channel, we estimate a 97.8% chance that the candidate is a true escapee from the Hyades. With a determined mass of 1.317 solar masses, this is potentially the most massive known single-evolution white dwarf and is by far the most massive with a strong association with an open cluster. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.03204v1-abstract-full').style.display = 'none'; document.getElementById('2310.03204v1-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 October, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">13 pages, 4 figures, 1 table. Accepted for publication in the Astrophysical Journal 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/2308.07430">arXiv:2308.07430</a> <span> [<a href="https://arxiv.org/pdf/2308.07430">pdf</a>, <a href="https://arxiv.org/format/2308.07430">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> </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/s41586-023-06171-9">10.1038/s41586-023-06171-9 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A rotating white dwarf shows different compositions on its opposite faces </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Caiazzo%2C+I">Ilaria Caiazzo</a>, <a href="/search/astro-ph?searchtype=author&query=Burdge%2C+K+B">Kevin B. Burdge</a>, <a href="/search/astro-ph?searchtype=author&query=Tremblay%2C+P">Pier-Emmanuel Tremblay</a>, <a href="/search/astro-ph?searchtype=author&query=Fuller%2C+J">James Fuller</a>, <a href="/search/astro-ph?searchtype=author&query=Ferrario%2C+L">Lilia Ferrario</a>, <a href="/search/astro-ph?searchtype=author&query=Gaensicke%2C+B+T">Boris T. Gaensicke</a>, <a href="/search/astro-ph?searchtype=author&query=Hermes%2C+J+J">J. J. Hermes</a>, <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Kawka%2C+A">Adela Kawka</a>, <a href="/search/astro-ph?searchtype=author&query=Kulkarni%2C+S+R">S. R. Kulkarni</a>, <a href="/search/astro-ph?searchtype=author&query=Marsh%2C+T+R">Thomas R. Marsh</a>, <a href="/search/astro-ph?searchtype=author&query=Mroz%2C+P">Przemek Mroz</a>, <a href="/search/astro-ph?searchtype=author&query=Prince%2C+T+A">Thomas A. Prince</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Rodriguez%2C+A+C">Antonio C. Rodriguez</a>, <a href="/search/astro-ph?searchtype=author&query=van+Roestel%2C+J">Jan van Roestel</a>, <a href="/search/astro-ph?searchtype=author&query=Vanderbosch%2C+Z+P">Zachary P. Vanderbosch</a>, <a href="/search/astro-ph?searchtype=author&query=Vennes%2C+S">Stephane Vennes</a>, <a href="/search/astro-ph?searchtype=author&query=Wickramasinghe%2C+D">Dayal Wickramasinghe</a>, <a href="/search/astro-ph?searchtype=author&query=Dhillon%2C+V+S">Vikram S. Dhillon</a>, <a href="/search/astro-ph?searchtype=author&query=Littlefair%2C+S+P">Stuart P. Littlefair</a>, <a href="/search/astro-ph?searchtype=author&query=Munday%2C+J">James Munday</a>, <a href="/search/astro-ph?searchtype=author&query=Pelisoli%2C+I">Ingrid Pelisoli</a>, <a href="/search/astro-ph?searchtype=author&query=Perley%2C+D">Daniel Perley</a>, <a href="/search/astro-ph?searchtype=author&query=Bellm%2C+E+C">Eric C. Bellm</a> , et al. (13 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="2308.07430v1-abstract-short" style="display: inline;"> White dwarfs, the extremely dense remnants left behind by most stars after their death, are characterised by a mass comparable to that of the Sun compressed into the size of an Earth-like planet. In the resulting strong gravity, heavy elements sink toward the centre and the upper layer of the atmosphere contains only the lightest element present, usually hydrogen or helium. Several mechanisms comp… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.07430v1-abstract-full').style.display = 'inline'; document.getElementById('2308.07430v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2308.07430v1-abstract-full" style="display: none;"> White dwarfs, the extremely dense remnants left behind by most stars after their death, are characterised by a mass comparable to that of the Sun compressed into the size of an Earth-like planet. In the resulting strong gravity, heavy elements sink toward the centre and the upper layer of the atmosphere contains only the lightest element present, usually hydrogen or helium. Several mechanisms compete with gravitational settling to change a white dwarf's surface composition as it cools, and the fraction of white dwarfs with helium atmospheres is known to increase by a factor ~2.5 below a temperature of about 30,000 K; therefore, some white dwarfs that appear to have hydrogen-dominated atmospheres above 30,000 K are bound to transition to be helium-dominated as they cool below it. Here we report observations of ZTF J203349.8+322901.1, a transitioning white dwarf with two faces: one side of its atmosphere is dominated by hydrogen and the other one by helium. This peculiar nature is likely caused by the presence of a small magnetic field, which creates an inhomogeneity in temperature, pressure or mixing strength over the surface. ZTF J203349.8+322901.1 might be the most extreme member of a class of magnetic, transitioning white dwarfs -- together with GD 323, a white dwarf that shows similar but much more subtle variations. This new class could help shed light on the physical mechanisms behind white dwarf spectral evolution. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.07430v1-abstract-full').style.display = 'none'; document.getElementById('2308.07430v1-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 August, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">45 pages, 11 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature 620, 61-66 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2203.11264">arXiv:2203.11264</a> <span> [<a href="https://arxiv.org/pdf/2203.11264">pdf</a>, <a href="https://arxiv.org/format/2203.11264">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/2041-8213/ac6585">10.3847/2041-8213/ac6585 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> When Do Stars Go BOOM? </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Cohen%2C+R+E">Roger E. Cohen</a>, <a href="/search/astro-ph?searchtype=author&query=Correnti%2C+M">Matteo Correnti</a>, <a href="/search/astro-ph?searchtype=author&query=Caiazzo%2C+I">Ilaria Caiazzo</a>, <a href="/search/astro-ph?searchtype=author&query=Cummings%2C+J">Jeffrey Cummings</a>, <a href="/search/astro-ph?searchtype=author&query=Goudfrooij%2C+P">Paul Goudfrooij</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M+S">Bradley M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Peeples%2C+M">Molly Peeples</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J">Jason Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Sabbi%2C+E">Elena Sabbi</a>, <a href="/search/astro-ph?searchtype=author&query=Tremblay%2C+P">Pier-Emmanuel Tremblay</a>, <a href="/search/astro-ph?searchtype=author&query=Williams%2C+B">Benjamin Williams</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="2203.11264v2-abstract-short" style="display: inline;"> The maximum mass of a star that can produce a white dwarf (WD) is an important astrophysical quantity. One of the best approaches to establishing this limit is to search for WDs in young star clusters in which only massive stars have had time to evolve and where the mass of the progenitor can be established from the cooling time of the WD together with the age of the cluster. Searches in young Mil… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.11264v2-abstract-full').style.display = 'inline'; document.getElementById('2203.11264v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2203.11264v2-abstract-full" style="display: none;"> The maximum mass of a star that can produce a white dwarf (WD) is an important astrophysical quantity. One of the best approaches to establishing this limit is to search for WDs in young star clusters in which only massive stars have had time to evolve and where the mass of the progenitor can be established from the cooling time of the WD together with the age of the cluster. Searches in young Milky Way clusters have not thus far yielded WD members more massive than about 1.1$~M_{\odot}$, well below the Chandrasekhar mass of $1.38~M_{\odot}$, nor progenitors with masses in excess of about $6~M_{\odot}$. However, the hunt for potentially massive WDs that escaped their cluster environs is yielding interesting candidates. To expand the cluster sample further, we used HST to survey four young and massive star clusters in the Magellanic Clouds for bright WDs that could have evolved from stars as massive as 10$~M_{\odot}$. We located five potential WD candidates in the oldest of the four clusters examined, the first extragalactic single WDs thus far discovered. As these hot WDs are very faint at optical wavelengths, final confirmation will likely have to await spectroscopy with 30-metre class telescopes. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.11264v2-abstract-full').style.display = 'none'; document.getElementById('2203.11264v2-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 April, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 21 March, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 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">10 pages, 5 figures, accepted to the Astrophysical Journal 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/2107.08458">arXiv:2107.08458</a> <span> [<a href="https://arxiv.org/pdf/2107.08458">pdf</a>, <a href="https://arxiv.org/format/2107.08458">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/s41586-021-03615-y">10.1038/s41586-021-03615-y <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A highly magnetised and rapidly rotating white dwarf as small as the Moon </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Caiazzo%2C+I">Ilaria Caiazzo</a>, <a href="/search/astro-ph?searchtype=author&query=Burdge%2C+K+B">Kevin B. Burdge</a>, <a href="/search/astro-ph?searchtype=author&query=Fuller%2C+J">James Fuller</a>, <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Kulkarni%2C+S+R">S. R. Kulkarni</a>, <a href="/search/astro-ph?searchtype=author&query=Prince%2C+T+A">Thomas A. Prince</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Schwab%2C+J">Josiah Schwab</a>, <a href="/search/astro-ph?searchtype=author&query=Andreoni%2C+I">Igor Andreoni</a>, <a href="/search/astro-ph?searchtype=author&query=Bellm%2C+E+C">Eric C. Bellm</a>, <a href="/search/astro-ph?searchtype=author&query=Drake%2C+A">Andrew Drake</a>, <a href="/search/astro-ph?searchtype=author&query=Duev%2C+D+A">Dmitry A. Duev</a>, <a href="/search/astro-ph?searchtype=author&query=Graham%2C+M+J">Matthew J. Graham</a>, <a href="/search/astro-ph?searchtype=author&query=Helou%2C+G">George Helou</a>, <a href="/search/astro-ph?searchtype=author&query=Mahabal%2C+A+A">Ashish A. Mahabal</a>, <a href="/search/astro-ph?searchtype=author&query=Masci%2C+F+J">Frank J. Masci</a>, <a href="/search/astro-ph?searchtype=author&query=Smith%2C+R">Roger Smith</a>, <a href="/search/astro-ph?searchtype=author&query=Soumagnac%2C+M+T">Maayane T. Soumagnac</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2107.08458v1-abstract-short" style="display: inline;"> White dwarfs represent the last stage of evolution of stars with mass less than about eight times that of the Sun and, like other stars, are often found in binaries. If the orbital period of the binary is short enough, energy losses from gravitational-wave radiation can shrink the orbit until the two white dwarfs come into contact and merge. Depending on the component masses, the merger can lead t… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2107.08458v1-abstract-full').style.display = 'inline'; document.getElementById('2107.08458v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2107.08458v1-abstract-full" style="display: none;"> White dwarfs represent the last stage of evolution of stars with mass less than about eight times that of the Sun and, like other stars, are often found in binaries. If the orbital period of the binary is short enough, energy losses from gravitational-wave radiation can shrink the orbit until the two white dwarfs come into contact and merge. Depending on the component masses, the merger can lead to a supernova of type Ia or result in a massive white dwarf. In the latter case, the white dwarf remnant is expected to be highly magnetised because of the strong magnetic dynamo that should arise during the merger, and be rapidly spinning from the conservation of the orbital angular momentum. Here we report observations of a white dwarf, ZTF J190132.9+145808.7, that exhibits these properties, but to an extreme: a rotation period of 6.94 minutes, a magnetic field ranging between 600 megagauss and 900 megagauss over its surface, and a stellar radius of about 2,100 km, slightly larger than the radius of the Moon. Such a small radius implies that the star's mass is close to the maximum white-dwarf mass, or Chandrasekhar mass. ZTF J190132.9+145808.7 is likely to be cooling through the Urca processes (neutrino emission from electron capture on sodium) because of the high densities reached in its core. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2107.08458v1-abstract-full').style.display = 'none'; document.getElementById('2107.08458v1-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, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">37 pages, 9 figures, published in Nature on June 30, 2021</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature 595, 39-42 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2101.08300">arXiv:2101.08300</a> <span> [<a href="https://arxiv.org/pdf/2101.08300">pdf</a>, <a href="https://arxiv.org/format/2101.08300">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/abdeb7">10.3847/1538-4357/abdeb7 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Massive White Dwarfs in Young Star Clusters </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Caiazzo%2C+I">Ilaria Caiazzo</a>, <a href="/search/astro-ph?searchtype=author&query=Du%2C+H">Helen Du</a>, <a href="/search/astro-ph?searchtype=author&query=Grondin%2C+S">Steffani Grondin</a>, <a href="/search/astro-ph?searchtype=author&query=Hegarty%2C+J">James Hegarty</a>, <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Kerr%2C+R">Ronan Kerr</a>, <a href="/search/astro-ph?searchtype=author&query=Miller%2C+D+R">David R. Miller</a>, <a href="/search/astro-ph?searchtype=author&query=Thiele%2C+S">Sarah Thiele</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="2101.08300v1-abstract-short" style="display: inline;"> We have carried out a search for massive white dwarfs (WDs) in the direction of young open star clusters using the Gaia DR2 database. The aim of this survey was to provide robust data for new and previously known high-mass WDs regarding cluster membership, to highlight WDs previously included in the Initial Final Mass Relation (IFMR) that are unlikely members of their respective clusters according… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2101.08300v1-abstract-full').style.display = 'inline'; document.getElementById('2101.08300v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2101.08300v1-abstract-full" style="display: none;"> We have carried out a search for massive white dwarfs (WDs) in the direction of young open star clusters using the Gaia DR2 database. The aim of this survey was to provide robust data for new and previously known high-mass WDs regarding cluster membership, to highlight WDs previously included in the Initial Final Mass Relation (IFMR) that are unlikely members of their respective clusters according to Gaia astrometry and to select an unequivocal WD sample that could then be compared with the host clusters' turnoff masses. All promising WD candidates in each cluster CMD were followed up with spectroscopy from Gemini in order to determine whether they were indeed WDs and derive their masses, temperatures and ages. In order to be considered cluster members, white dwarfs were required to have proper motions and parallaxes within 2, 3, or 4-$蟽$ of that of their potential parent cluster based on how contaminated the field was in their region of the sky, have a cooling age that was less than the cluster age and a mass that was broadly consistent with the IFMR. A number of WDs included in current versions of the IFMR turned out to be non-members and a number of apparent members, based on Gaia's astrometric data alone, were rejected as their mass and/or cooling times were incompatible with cluster membership. In this way, we developed a highly selected IFMR sample for high mass WDs that, surprisingly, contained no precursor masses significantly in excess of ${\sim}$6 $M_{\odot}$. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2101.08300v1-abstract-full').style.display = 'none'; document.getElementById('2101.08300v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 20 January, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 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">39 pages, 17 figures, Accepted for Publication in 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/1906.04727">arXiv:1906.04727</a> <span> [<a href="https://arxiv.org/pdf/1906.04727">pdf</a>, <a href="https://arxiv.org/format/1906.04727">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/ab2874">10.3847/1538-4357/ab2874 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Massive Magnetic Helium Atmosphere White Dwarf Binary in a Young Star Cluster </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Kerr%2C+R+M">Ronan M. Kerr</a>, <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Caiazzo%2C+I">Ilaria Caiazzo</a>, <a href="/search/astro-ph?searchtype=author&query=Cummings%2C+J">Jeffrey Cummings</a>, <a href="/search/astro-ph?searchtype=author&query=Bergeron%2C+P">Pierre Bergeron</a>, <a href="/search/astro-ph?searchtype=author&query=Dufour%2C+P">Patrick Dufour</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="1906.04727v1-abstract-short" style="display: inline;"> We have searched the Gaia DR2 catalogue for previously unknown hot white dwarfs in the direction of young open star clusters. The aim of this experiment was to try and extend the initial-final mass relation (IFMR) to somewhat higher masses, potentially providing a tension with the Chandrasekhar limit currently thought to be around 1.38 M$_{\odot}$. We discovered a particularly interesting white dw… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1906.04727v1-abstract-full').style.display = 'inline'; document.getElementById('1906.04727v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1906.04727v1-abstract-full" style="display: none;"> We have searched the Gaia DR2 catalogue for previously unknown hot white dwarfs in the direction of young open star clusters. The aim of this experiment was to try and extend the initial-final mass relation (IFMR) to somewhat higher masses, potentially providing a tension with the Chandrasekhar limit currently thought to be around 1.38 M$_{\odot}$. We discovered a particularly interesting white dwarf in the direction of the young $\sim$150 Myr old cluster Messier 47 (NGC 2422). All Gaia indicators (proper motion, parallax, location in the Gaia colour-magnitude diagram) suggest that it is a cluster member. Its spectrum, obtained from Gemini South, yields a number of anomalies: it is a DB (helium-rich atmosphere) white dwarf, it has a large magnetic field (2.5 MG), is of high mass ($\sim$1.06 M$_\odot$) and its colours are very peculiar --- particularly the redder ones ($r$, $i$, $z$ and $y$), which suggest that it has a late-type companion. This is the only magnetized, detached binary white dwarf with a non-degenerate companion of any spectral type known in or out of a star cluster. If the white dwarf is a cluster member, as all indicators suggest, its progenitor had a mass just over 6 M$_\odot$. It may, however, be telling an even more interesting story than the one related to the IFMR, one about the origin of stellar magnetic fields, Type I supernovae and gravitational waves from low mass stellar systems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1906.04727v1-abstract-full').style.display = 'none'; document.getElementById('1906.04727v1-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, 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">10 pages, 7 figures, accepted for publication in 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/1901.07230">arXiv:1901.07230</a> <span> [<a href="https://arxiv.org/pdf/1901.07230">pdf</a>, <a href="https://arxiv.org/ps/1901.07230">ps</a>, <a href="https://arxiv.org/format/1901.07230">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnras/stz277">10.1093/mnras/stz277 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The HST Large Programme on NGC6752. II. Multiple populations at the bottom of the main sequence probed in NIR </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Milone%2C+A+P">A. P. Milone</a>, <a href="/search/astro-ph?searchtype=author&query=Marino%2C+A+F">A. F. Marino</a>, <a href="/search/astro-ph?searchtype=author&query=Bedin%2C+L+R">L. R. Bedin</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J">J. Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=Apai%2C+D">D. Apai</a>, <a href="/search/astro-ph?searchtype=author&query=Bellini%2C+A">A. Bellini</a>, <a href="/search/astro-ph?searchtype=author&query=Dieball%2C+A">A. Dieball</a>, <a href="/search/astro-ph?searchtype=author&query=Salaris%2C+M">M. Salaris</a>, <a href="/search/astro-ph?searchtype=author&query=Libralato%2C+M">M. Libralato</a>, <a href="/search/astro-ph?searchtype=author&query=Nardiello%2C+D">D. Nardiello</a>, <a href="/search/astro-ph?searchtype=author&query=Bergeron%2C+P">P. Bergeron</a>, <a href="/search/astro-ph?searchtype=author&query=Burgasser%2C+A+J">A. J. Burgasser</a>, <a href="/search/astro-ph?searchtype=author&query=Rees%2C+J+M">J. M. Rees</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. M. Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">H. B. Richer</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="1901.07230v1-abstract-short" style="display: inline;"> Historically, multiple populations in Globular Clusters (GCs) have been mostly studied from ultraviolet and optical filters down to stars that are more massive than ~0.6 solar masses. Here we exploit deep near-infrared (NIR) photometry from the Hubble Space Telescope to investigate multiple populations among M-dwarfs in the GC NGC6752. We discovered that the three main populations (A, B and C), pr… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1901.07230v1-abstract-full').style.display = 'inline'; document.getElementById('1901.07230v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1901.07230v1-abstract-full" style="display: none;"> Historically, multiple populations in Globular Clusters (GCs) have been mostly studied from ultraviolet and optical filters down to stars that are more massive than ~0.6 solar masses. Here we exploit deep near-infrared (NIR) photometry from the Hubble Space Telescope to investigate multiple populations among M-dwarfs in the GC NGC6752. We discovered that the three main populations (A, B and C), previously observed in the brightest part of the color-magnitude diagram, define three distinct sequences that run from the main-sequence (MS) knee towards the bottom of the MS (~0.15 solar masses). These results, together with similar findings on NGC2808, M4, and omega Centauri, demonstrate that multiple sequences of M-dwarfs are common features of the color-magnitude diagrams of GCs. The three sequences of low-mass stars in NGC6752 are consistent with stellar populations with different oxygen abundances. The range of [O/Fe] needed to reproduce the NIR CMD of NGC6752 is similar to the oxygen spread inferred from high-resolution spectroscopy of red-giant branch (RGB) stars. The relative numbers of stars in the three populations of M-dwarfs are similar to those derived among RGB and MS stars more massive than ~0.6 solar masses. As a consequence, the evidence that the properties of multiple populations do not depend on stellar mass is a constraint for the formation scenarios. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1901.07230v1-abstract-full').style.display = 'none'; document.getElementById('1901.07230v1-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, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 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">7 pages, 5 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/1502.07306">arXiv:1502.07306</a> <span> [<a href="https://arxiv.org/pdf/1502.07306">pdf</a>, <a href="https://arxiv.org/format/1502.07306">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/810/2/127">10.1088/0004-637X/810/2/127 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> When do stars in 47 Tucanae lose their mass? </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J">Jason Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Marigo%2C+P">Paola Marigo</a>, <a href="/search/astro-ph?searchtype=author&query=Antolini%2C+E">Elisa Antolini</a>, <a href="/search/astro-ph?searchtype=author&query=Goldsbury%2C+R">Ryan Goldsbury</a>, <a href="/search/astro-ph?searchtype=author&query=Parada%2C+J">Javiera Parada</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="1502.07306v2-abstract-short" style="display: inline;"> By examining the diffusion of young white dwarfs through the core of the globular cluster 47 Tucanae, we estimate the time when the progenitor star lost the bulk of its mass to become a white dwarf. According to stellar evolution models of the white-dwarf progenitors in 47 Tucanae, we find this epoch to coincide approximately with the star ascending the asymptotic giant branch ($3.0 \pm 8.1$ Myr b… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1502.07306v2-abstract-full').style.display = 'inline'; document.getElementById('1502.07306v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1502.07306v2-abstract-full" style="display: none;"> By examining the diffusion of young white dwarfs through the core of the globular cluster 47 Tucanae, we estimate the time when the progenitor star lost the bulk of its mass to become a white dwarf. According to stellar evolution models of the white-dwarf progenitors in 47 Tucanae, we find this epoch to coincide approximately with the star ascending the asymptotic giant branch ($3.0 \pm 8.1$ Myr before the tip of the AGB) and more than ninety million years after the helium flash (with ninety-percent confidence). From the diffusion of the young white dwarfs we can exclude the hypothesis that the bulk of the mass loss occurs on the red-giant branch at the four-sigma level. Furthermore, we find that the radial distribution of horizontal branch stars is consistent with that of the red-giant stars and upper-main-sequence stars and inconsistent with the loss of more than 0.2 solar masses on the red-giant branch at the six-sigma level. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1502.07306v2-abstract-full').style.display = 'none'; document.getElementById('1502.07306v2-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 August, 2015; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 February, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 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">8 pages, 4 figures, version 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/1502.01890">arXiv:1502.01890</a> <span> [<a href="https://arxiv.org/pdf/1502.01890">pdf</a>, <a href="https://arxiv.org/format/1502.01890">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/804/1/53">10.1088/0004-637X/804/1/53 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Measurement of Diffusion in 47 Tucanae </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Antolini%2C+E">Elisa Antolini</a>, <a href="/search/astro-ph?searchtype=author&query=Goldsbury%2C+R">Ryan Goldsbury</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J">Jason Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Parada%2C+J">Javiera Parada</a>, <a href="/search/astro-ph?searchtype=author&query=Tremblay%2C+P">Pier-Emmanuel Tremblay</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="1502.01890v2-abstract-short" style="display: inline;"> Using images from the Hubble Space Telescope Wide-Field Camera 3, we measure the rate of diffusion of stars through the core of the globular cluster 47 Tucanae using a sample of young white dwarfs identified in these observations. This is the first direct measurement of diffusion due to gravitational relaxation. We find that the diffusion rate $魏\approx 10-13$ arcsecond$^2$ Myr$^{-1}$ is consisten… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1502.01890v2-abstract-full').style.display = 'inline'; document.getElementById('1502.01890v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1502.01890v2-abstract-full" style="display: none;"> Using images from the Hubble Space Telescope Wide-Field Camera 3, we measure the rate of diffusion of stars through the core of the globular cluster 47 Tucanae using a sample of young white dwarfs identified in these observations. This is the first direct measurement of diffusion due to gravitational relaxation. We find that the diffusion rate $魏\approx 10-13$ arcsecond$^2$ Myr$^{-1}$ is consistent with theoretical estimates of the relaxation time in the core of 47 Tucanae of about 70 Myr. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1502.01890v2-abstract-full').style.display = 'none'; document.getElementById('1502.01890v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 20 February, 2015; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 6 February, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 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">12 pages, 10 figures, accept for publication in the Astrophysical Journal (added a short passage on blue stragglers descendants and corrected a minor typographical error in Eq. 15)</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1310.0111">arXiv:1310.0111</a> <span> [<a href="https://arxiv.org/pdf/1310.0111">pdf</a>, <a href="https://arxiv.org/ps/1310.0111">ps</a>, <a href="https://arxiv.org/format/1310.0111">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/778/2/104">10.1088/0004-637X/778/2/104 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Comparing the White Dwarf Cooling Sequences in 47 Tuc and NGC 6397 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Goldsbury%2C+R">Ryan Goldsbury</a>, <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Hurley%2C+J">Jarrod Hurley</a>, <a href="/search/astro-ph?searchtype=author&query=Dotter%2C+A">Aaron Dotter</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jason S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Woodley%2C+K+A">Kristin A. Woodley</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">Gregory G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Shara%2C+M+M">Michael M. Shara</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="1310.0111v1-abstract-short" style="display: inline;"> Using deep Hubble Space Telescope imaging, color-magnitude diagrams are constructed for the globular clusters 47 Tuc and NGC 6397. As expected, because of its lower metal abundance, the main sequence of NGC 6397 lies well to the blue of that of 47 Tuc. A comparison of the white dwarf cooling sequences of the two clusters, however, demonstrates that these sequences are indistinguishable over most o… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1310.0111v1-abstract-full').style.display = 'inline'; document.getElementById('1310.0111v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1310.0111v1-abstract-full" style="display: none;"> Using deep Hubble Space Telescope imaging, color-magnitude diagrams are constructed for the globular clusters 47 Tuc and NGC 6397. As expected, because of its lower metal abundance, the main sequence of NGC 6397 lies well to the blue of that of 47 Tuc. A comparison of the white dwarf cooling sequences of the two clusters, however, demonstrates that these sequences are indistinguishable over most of their loci - a consequence of the settling out of heavy elements in the dense white dwarf atmosphere and the near equality of their masses. Lower quality data on M4 continues this trend to a third cluster whose metallicity is intermediate between these two. While the path of the white dwarfs in the color-magnitude diagram is nearly identical in 47 Tuc and NGC 6397, the numbers of white dwarfs along the path are not. This results from the relatively rapid relaxation in NGC 6397 compared to 47 Tuc and provides a cautionary note that simply counting objects in star clusters in random locations as a method of testing stellar evolutionary theory is likely dangerous unless dynamical considerations are included. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1310.0111v1-abstract-full').style.display = 'none'; document.getElementById('1310.0111v1-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 September, 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">7 pages, 4 figures, accepted for publication in 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/1308.0032">arXiv:1308.0032</a> <span> [<a href="https://arxiv.org/pdf/1308.0032">pdf</a>, <a href="https://arxiv.org/ps/1308.0032">ps</a>, <a href="https://arxiv.org/format/1308.0032">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/nature12334">10.1038/nature12334 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> An Age Difference of 2 Gyr between a Metal-Rich and a Metal-Poor Globular Cluster </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M+S">B. M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">J. S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J">J. Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=Dotter%2C+A">A. Dotter</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">H. B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. M. Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Shara%2C+M+M">M. M. Shara</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">G. G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Hurley%2C+J+R">J. R. Hurley</a>, <a href="/search/astro-ph?searchtype=author&query=King%2C+I+R">I. R. King</a>, <a href="/search/astro-ph?searchtype=author&query=Reitzel%2C+D">D. Reitzel</a>, <a href="/search/astro-ph?searchtype=author&query=Stetson%2C+P+B">P. B. Stetson</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1308.0032v1-abstract-short" style="display: inline;"> Globular clusters trace the formation history of the spheroidal components of both our Galaxy and others, which represent the bulk of star formation over the history of the universe. They also exhibit a range of metallicities, with metal-poor clusters dominating the stellar halo of the Galaxy, and higher metallicity clusters found within the inner Galaxy, associated with the stellar bulge, or the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1308.0032v1-abstract-full').style.display = 'inline'; document.getElementById('1308.0032v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1308.0032v1-abstract-full" style="display: none;"> Globular clusters trace the formation history of the spheroidal components of both our Galaxy and others, which represent the bulk of star formation over the history of the universe. They also exhibit a range of metallicities, with metal-poor clusters dominating the stellar halo of the Galaxy, and higher metallicity clusters found within the inner Galaxy, associated with the stellar bulge, or the thick disk. Age differences between these clusters can indicate the sequence in which the components of the Galaxy formed, and in particular which clusters were formed outside the Galaxy and later swallowed along with their original host galaxies, and which were formed in situ. Here we present an age determination of the metal-rich globular cluster 47 Tucanae by fitting the properties of the cluster white dwarf population, which implies an absolute age of 9.9 (0.7) Gyr at 95% confidence. This is about 2.0 Gyr younger than inferred for the metal-poor cluster NGC 6397 from the same models, and provides quantitative evidence that metal-rich clusters like 47 Tucanae formed later than the metal-poor halo clusters like NGC 6397. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1308.0032v1-abstract-full').style.display = 'none'; document.getElementById('1308.0032v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 31 July, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2013. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Main Article: 10 pages, 4 figures; Supplementary Info 15 pages, 5 figures. Nature, Aug 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/1306.1226">arXiv:1306.1226</a> <span> [<a href="https://arxiv.org/pdf/1306.1226">pdf</a>, <a href="https://arxiv.org/ps/1306.1226">ps</a>, <a href="https://arxiv.org/format/1306.1226">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/10.1088/2041-8205/771/1/L15">10.1088/2041-8205/771/1/L15 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Dynamical Signature of Multiple Stellar Populations in 47 Tucanae </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J">Jay Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jason S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Shara%2C+M+M">Michael M. Shara</a>, <a href="/search/astro-ph?searchtype=author&query=Dotter%2C+A">Aaron Dotter</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">Gregory G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</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="1306.1226v1-abstract-short" style="display: inline;"> Based on the width of its main sequence, and an actual observed split when viewed through particular filters, it is widely accepted that 47 Tucanae contains multiple stellar populations. In this contribution, we divide the main-sequence of 47 Tuc into four color groups, which presumably represent stars of various chemical compositions. The kinematic properties of each of these groups is explored v… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1306.1226v1-abstract-full').style.display = 'inline'; document.getElementById('1306.1226v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1306.1226v1-abstract-full" style="display: none;"> Based on the width of its main sequence, and an actual observed split when viewed through particular filters, it is widely accepted that 47 Tucanae contains multiple stellar populations. In this contribution, we divide the main-sequence of 47 Tuc into four color groups, which presumably represent stars of various chemical compositions. The kinematic properties of each of these groups is explored via proper-motions, and a strong signal emerges of differing proper-motion anisotropies with differing main-sequence color; the bluest main-sequence stars exhibit the largest proper-motion anisotropy which becomes undetectable for the reddest stars. In addition, the bluest stars are also the most centrally concentrated. A simiilar analysis for SMC stars, which are located in the background of 47 Tuc on our frames, yields none of the anisotropy exhibited by the 47 Tuc stars. We discuss implications of these results for possible formation scenarios of the various populations. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1306.1226v1-abstract-full').style.display = 'none'; document.getElementById('1306.1226v1-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 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 for publication in the Astrophysical Journal Letters, 5 pages, 4 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/1212.1159">arXiv:1212.1159</a> <span> [<a href="https://arxiv.org/pdf/1212.1159">pdf</a>, <a href="https://arxiv.org/ps/1212.1159">ps</a>, <a href="https://arxiv.org/format/1212.1159">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/763/2/110">10.1088/0004-637X/763/2/110 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Ultra-Deep Hubble Space Telescope Imaging of the Small Magellanic Cloud: The Initial Mass Function of Stars with M <~ 1 Msun </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jason S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J">Jay Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=Dotter%2C+A">Aaron Dotter</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">Gregory G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M+S">Brad M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Hurley%2C+J">Jarrod Hurley</a>, <a href="/search/astro-ph?searchtype=author&query=Reid%2C+I+N">I. Neill Reid</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Shara%2C+M+M">Michael M. Shara</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="1212.1159v2-abstract-short" style="display: inline;"> We present a new measurement of the stellar initial mass function (IMF) based on ultra-deep, high-resolution photometry of >5,000 stars in the outskirts of the Small Magellanic Cloud (SMC) galaxy. The Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) observations reveal this rich, co-spatial population behind the foreground globular cluster 47 Tuc, which we targeted for 121 HST orbits… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1212.1159v2-abstract-full').style.display = 'inline'; document.getElementById('1212.1159v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1212.1159v2-abstract-full" style="display: none;"> We present a new measurement of the stellar initial mass function (IMF) based on ultra-deep, high-resolution photometry of >5,000 stars in the outskirts of the Small Magellanic Cloud (SMC) galaxy. The Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) observations reveal this rich, co-spatial population behind the foreground globular cluster 47 Tuc, which we targeted for 121 HST orbits. The stellar main sequence of the SMC is measured in the F606W, F814W color-magnitude diagram (CMD) down to ~30th magnitude, and is cleanly separated from the foreground star cluster population using proper motions. We simulate the SMC population by extracting stellar masses (single and unresolved binaries) from specific IMFs, and converting those masses to luminosities in our bandpasses. The corresponding photometry for these simulated stars is drawn directly from a rich cloud of 4 million artificial stars, thereby accounting for the real photometric scatter and completeness of the data. Over a continuous and well populated mass range of M = 0.37 - 0.93 Msun (i.e., down to a ~75% completeness limit at F606W = 28.7), we demonstrate that the IMF is well represented by a single power-law form with slope 伪= -1.90 (^{+0.15}_{-0.10}) (3 sigma error) (i.e., dN/dM \propto M^伪). This is shallower than the Salpeter slope of 伪= -2.35, which agrees with the observed stellar luminosity function at higher masses. Our results indicate that the IMF does {\it not} turn over to a more shallow power-law form within this mass range. We discuss implications of this result for the theory of star formation, the inferred masses of galaxies, and the (lack of a) variation of the IMF with metallicity. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1212.1159v2-abstract-full').style.display = 'none'; document.getElementById('1212.1159v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 31 December, 2012; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 5 December, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 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">9 pages, 5 figures, 1 table. Accepted for publication in ApJ. Minor revisions to second version based on ApJ proofs. Error bar on IMF slope clarified as 3-sigma interval</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1209.4901">arXiv:1209.4901</a> <span> [<a href="https://arxiv.org/pdf/1209.4901">pdf</a>, <a href="https://arxiv.org/ps/1209.4901">ps</a>, <a href="https://arxiv.org/format/1209.4901">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/760/1/78">10.1088/0004-637X/760/1/78 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> An Empirical Measure of the Rate of White Dwarf Cooling in 47 Tucanae </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Goldsbury%2C+R">R. Goldsbury</a>, <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">J. Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">H. B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Bergeron%2C+P">P. Bergeron</a>, <a href="/search/astro-ph?searchtype=author&query=Dotter%2C+A">A. Dotter</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">J. S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=MacDonald%2C+J">J. MacDonald</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. M. Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Stetson%2C+P+B">P. B. Stetson</a>, <a href="/search/astro-ph?searchtype=author&query=Tremblay%2C+P+-">P. -E. Tremblay</a>, <a href="/search/astro-ph?searchtype=author&query=Woodley%2C+K+A">K. A. Woodley</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="1209.4901v1-abstract-short" style="display: inline;"> We present an empirical determination of the white dwarf cooling sequence in the globular cluster 47 Tucanae. Using spectral models, we determine temperatures for 887 objects from Wide Field Camera 3 data, as well as 292 objects from data taken with the Advanced Camera for Surveys. We make the assumption that the rate of white dwarf formation in the cluster is constant. Stellar evolution models ar… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1209.4901v1-abstract-full').style.display = 'inline'; document.getElementById('1209.4901v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1209.4901v1-abstract-full" style="display: none;"> We present an empirical determination of the white dwarf cooling sequence in the globular cluster 47 Tucanae. Using spectral models, we determine temperatures for 887 objects from Wide Field Camera 3 data, as well as 292 objects from data taken with the Advanced Camera for Surveys. We make the assumption that the rate of white dwarf formation in the cluster is constant. Stellar evolution models are then used to determine the rate at which objects are leaving the main sequence, which must be the same as the rate at which objects are arriving on the white dwarf sequence in our field. The result is an empirically derived relation between temperature ($T_{eff}$) and time ($t$) on the white dwarf cooling sequence. Comparing this result to theoretical cooling models, we find general agreement with the expected slopes between 20,000K and 30,000K and between 6,000K and 20,000K, but the transition to the Mestel cooling rate of $T_{eff} \propto t^{-0.4}$ is found to occur at hotter temperatures, and more abruptly than is predicted by any of these models. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1209.4901v1-abstract-full').style.display = 'none'; document.getElementById('1209.4901v1-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 September, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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">10 pages, 16 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/1203.5336">arXiv:1203.5336</a> <span> [<a href="https://arxiv.org/pdf/1203.5336">pdf</a>, <a href="https://arxiv.org/ps/1203.5336">ps</a>, <a href="https://arxiv.org/format/1203.5336">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/2041-8205/751/1/L12">10.1088/2041-8205/751/1/L12 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Proper Motions and Internal Dynamics in the Core of the Globular Cluster M71 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Samra%2C+R+S">Raminder Singh Samra</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J+S">Jeremy S. Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Goldsbury%2C+R">Ryan Goldsbury</a>, <a href="/search/astro-ph?searchtype=author&query=Thanjavur%2C+K+G">Karun G. Thanjavur</a>, <a href="/search/astro-ph?searchtype=author&query=Walker%2C+G+A">Gordon A. Walker</a>, <a href="/search/astro-ph?searchtype=author&query=Woodley%2C+K+A">Kristin A. Woodley</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="1203.5336v1-abstract-short" style="display: inline;"> We have used Gemini North together with the NIRI-ALTAIR adaptive optics imager in the H and K bands to explore the core of the Galactic globular cluster M71 (NGC 6838). We obtained proper motions for 217 stars and have resolved its internal proper motion dispersion. Using a 3.8 year baseline, the proper motion dispersion in the core is found to be 179 +/- 17 microarcsec/yr. We find no evidence of… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1203.5336v1-abstract-full').style.display = 'inline'; document.getElementById('1203.5336v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1203.5336v1-abstract-full" style="display: none;"> We have used Gemini North together with the NIRI-ALTAIR adaptive optics imager in the H and K bands to explore the core of the Galactic globular cluster M71 (NGC 6838). We obtained proper motions for 217 stars and have resolved its internal proper motion dispersion. Using a 3.8 year baseline, the proper motion dispersion in the core is found to be 179 +/- 17 microarcsec/yr. We find no evidence of anisotropy in the motions and no radial variation in the proper motions with respect to distance from the cluster center. We also set an upper limit on any central black hole to be ~150 Msun at 90% confidence level. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1203.5336v1-abstract-full').style.display = 'none'; document.getElementById('1203.5336v1-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 March, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 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">5 pages, 4 figures, accepted for publication in Astrophysical Journal 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/1112.1426">arXiv:1112.1426</a> <span> [<a href="https://arxiv.org/pdf/1112.1426">pdf</a>, <a href="https://arxiv.org/ps/1112.1426">ps</a>, <a href="https://arxiv.org/format/1112.1426">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/0004-6256/143/1/11">10.1088/0004-6256/143/1/11 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Deep, Wide-Field, and Panchromatic View of 47 Tuc and the SMC with HST: Observations and Data Analysis Methods </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jason S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J">Jay Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=Dotter%2C+A">Aaron Dotter</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">Gregory G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M+S">Brad M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Hurley%2C+J">Jarrod Hurley</a>, <a href="/search/astro-ph?searchtype=author&query=King%2C+I+R">Ivan R. King</a>, <a href="/search/astro-ph?searchtype=author&query=Reitzel%2C+D">David Reitzel</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Shara%2C+M+M">Michael M. Shara</a>, <a href="/search/astro-ph?searchtype=author&query=Stetson%2C+P+B">Peter B. Stetson</a>, <a href="/search/astro-ph?searchtype=author&query=Woodley%2C+K+A">Kristin A. Woodley</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="1112.1426v1-abstract-short" style="display: inline;"> In HST Cycle 17, we imaged the well known globular star cluster 47 Tucanae for 121 orbits using ACS and both the UVIS and IR channels of WFC3 (GO-11677, PI - H. Richer). This unique data set was obtained to address many scientific questions that demand a very deep, panchromatic, and panoramic view of the cluster's stellar populations. In total, the program obtained over 0.75 Ms of imaging exposure… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1112.1426v1-abstract-full').style.display = 'inline'; document.getElementById('1112.1426v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1112.1426v1-abstract-full" style="display: none;"> In HST Cycle 17, we imaged the well known globular star cluster 47 Tucanae for 121 orbits using ACS and both the UVIS and IR channels of WFC3 (GO-11677, PI - H. Richer). This unique data set was obtained to address many scientific questions that demand a very deep, panchromatic, and panoramic view of the cluster's stellar populations. In total, the program obtained over 0.75 Ms of imaging exposure time with the three HST cameras, over a time span of 9 months in 2010. The primary ACS field was imaged in the two broadband filters F606W and F814W filters, at 13 orientations, for all 121 orbits. The parallel WFC3 imaging provides a panchromatic (0.4 - 1.7 micron) and contiguous imaging swath over a 250 degree azimuthal range at impact radii of 6.5 -- 17.9 pc in 47 Tuc. This imaging totals over 60 arcmin^2 in area and utilizes the F390W and F606W broadband filters on WFC3/UVIS and the F110W and F160W broadband filters on WFC3/IR. In this paper, we describe the observational design of the new survey and one of the methods used to analyze all of the imaging data. This analysis combines over 700 full-frame images taken with the three HST cameras into a handful of ultra-deep, well-sampled combined images in each of the six filters. The results reveal unprecedented color-magnitude diagrams (CMDs) of the cluster extending to >30th magnitude in the optical, 29th magnitude in the UV, and 27th magnitude in the IR. The data set provides a characterization of the complete stellar populations of 47 Tuc, extending from the faintest hydrogen burning dwarfs through the main-sequence and giant branches, down to very cool white dwarf remnants in the cluster. The imaging also provides the deepest probe of the stellar populations of the background Small Magellanic Cloud (SMC) galaxy, resolving low mass main-sequence dwarfs with M < 0.2 Msun. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1112.1426v1-abstract-full').style.display = 'none'; document.getElementById('1112.1426v1-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 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">Accepted for Publication in the Astronomical Journal. 23 pages, 13 figures, and 4 tables. Companion paper by K. Woodley is astro-ph/0374778</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> 2012, AJ, 143, 11 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1112.1425">arXiv:1112.1425</a> <span> [<a href="https://arxiv.org/pdf/1112.1425">pdf</a>, <a href="https://arxiv.org/ps/1112.1425">ps</a>, <a href="https://arxiv.org/format/1112.1425">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/10.1088/0004-6256/143/2/50">10.1088/0004-6256/143/2/50 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Spectral Energy Distributions of White Dwarfs in 47 Tucanae: The Distance to the Cluster </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Woodley%2C+K+A">K. A. Woodley</a>, <a href="/search/astro-ph?searchtype=author&query=Goldsbury%2C+R">R. Goldsbury</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">J. S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">H. B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Tremblay%2C+P+-">P. -E. Tremblay</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J">J. Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=Bergeron%2C+P">P. Bergeron</a>, <a href="/search/astro-ph?searchtype=author&query=Dotter%2C+A">A. Dotter</a>, <a href="/search/astro-ph?searchtype=author&query=Esteves%2C+L">L. Esteves</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">G. G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+.+M+S">. M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">J. Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Hurley%2C+J">J. Hurley</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. M. Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Shara%2C+M+M">M. M. Shara</a>, <a href="/search/astro-ph?searchtype=author&query=Stetson%2C+P+B">P. B. Stetson</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="1112.1425v1-abstract-short" style="display: inline;"> We present a new distance determination to the Galactic globular cluster 47 Tucanae by fitting the spectral energy distributions of its white dwarfs to pure hydrogen atmosphere white dwarf models. Our photometric dataset is obtained from a 121 orbit Hubble Space Telescope program using the Wide Field Camera 3 UVIS/IR channels, capturing F390W, F606W, F110W, and F160W images. These images cover mor… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1112.1425v1-abstract-full').style.display = 'inline'; document.getElementById('1112.1425v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1112.1425v1-abstract-full" style="display: none;"> We present a new distance determination to the Galactic globular cluster 47 Tucanae by fitting the spectral energy distributions of its white dwarfs to pure hydrogen atmosphere white dwarf models. Our photometric dataset is obtained from a 121 orbit Hubble Space Telescope program using the Wide Field Camera 3 UVIS/IR channels, capturing F390W, F606W, F110W, and F160W images. These images cover more than 60 square arcmins and extend over a radial range of 5-13.7 arcmin (6.5-17.9 pc) within the globular cluster. Using a likelihood analysis, we obtain a best fitting unreddened distance modulus of (m - M)o=13.36+/-0.02+/-0.06 corresponding to a distance of 4.70+/-0.04+/-0.13 kpc, where the first error is random and the second is systematic. We also search the white dwarf photometry for infrared excess in the F160W filter, indicative of debris disks or low mass companions, and find no convincing cases within our sample. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1112.1425v1-abstract-full').style.display = 'none'; document.getElementById('1112.1425v1-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 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">Accepted to The Astronomical Journal, 13 Figures, 2 Tables. Figures 3 and 6 are figure sets, each composed of 59 subfigures (to appear in the electronic journal). This is a Companion paper to the article ID: submit/0375614</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1102.3501">arXiv:1102.3501</a> <span> [<a href="https://arxiv.org/pdf/1102.3501">pdf</a>, <a href="https://arxiv.org/format/1102.3501">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/0004-637X/731/2/124">10.1088/0004-637X/731/2/124 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Density Variations in the NW Star Stream of M31 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Carlberg%2C+R+G">R. G. Carlberg</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=McConnachie%2C+A+W">Alan W. McConnachie</a>, <a href="/search/astro-ph?searchtype=author&query=Irwin%2C+M">Mike Irwin</a>, <a href="/search/astro-ph?searchtype=author&query=Ibata%2C+R+A">Rodrigo A. Ibata</a>, <a href="/search/astro-ph?searchtype=author&query=Dotter%2C+A+L">Aaron L. Dotter</a>, <a href="/search/astro-ph?searchtype=author&query=Chapman%2C+S">Scott Chapman</a>, <a href="/search/astro-ph?searchtype=author&query=Fardal%2C+M">Mark Fardal</a>, <a href="/search/astro-ph?searchtype=author&query=Ferguson%2C+A+M+N">A. M. N. Ferguson</a>, <a href="/search/astro-ph?searchtype=author&query=Lewis%2C+G+F">G. F. Lewis</a>, <a href="/search/astro-ph?searchtype=author&query=Navarro%2C+J+F">Julio F. Navarro</a>, <a href="/search/astro-ph?searchtype=author&query=Puzia%2C+T+H">Thomas H. Puzia</a>, <a href="/search/astro-ph?searchtype=author&query=Valls-Gabaud%2C+D">David Valls-Gabaud</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="1102.3501v1-abstract-short" style="display: inline;"> The Pan Andromeda Archeological Survey (PAndAS) CFHT Megaprime survey of the M31-M33 system has found a star stream which extends about 120 kpc NW from the center of M31. The great length of the stream, and the likelihood that it does not significantly intersect the disk of M31, means that it is unusually well suited for a measurement of stream gaps and clumps along its length as a test for the pr… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1102.3501v1-abstract-full').style.display = 'inline'; document.getElementById('1102.3501v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1102.3501v1-abstract-full" style="display: none;"> The Pan Andromeda Archeological Survey (PAndAS) CFHT Megaprime survey of the M31-M33 system has found a star stream which extends about 120 kpc NW from the center of M31. The great length of the stream, and the likelihood that it does not significantly intersect the disk of M31, means that it is unusually well suited for a measurement of stream gaps and clumps along its length as a test for the predicted thousands of dark matter sub-halos. The main result of this paper is that the density of the stream varies between zero and about three times the mean along its length on scales of 2 to 20 kpc. The probability that the variations are random fluctuations in the star density is less than 10^-5. As a control sample we search for density variations at precisely the same location in stars with metallicity higher than the stream, [Fe/H]=[0, -0.5] and find no variations above the expected shot noise. The lumpiness of the stream is not compatible with a low mass star stream in a smooth galactic potential, nor is it readily compatible with the disturbance caused by the visible M31 satellite galaxies. The stream's density variations appear to be consistent with the effects of a large population of steep mass function dark matter sub-halos, such as found in LCDM simulations, acting on an approximately 10Gyr old star stream. The effects of a single set of halo substructure realizations are shown for illustration, reserving a statistical comparison for another study. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1102.3501v1-abstract-full').style.display = 'none'; document.getElementById('1102.3501v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 17 February, 2011; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 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">ApJ revised version submitted</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> 2011 ApJ, 731, 124 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1008.2755">arXiv:1008.2755</a> <span> [<a href="https://arxiv.org/pdf/1008.2755">pdf</a>, <a href="https://arxiv.org/format/1008.2755">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/10.1088/0004-6256/140/6/1830">10.1088/0004-6256/140/6/1830 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Goldsbury%2C+R">Ryan Goldsbury</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J">Jay Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=Dotter%2C+A">Aaron Dotter</a>, <a href="/search/astro-ph?searchtype=author&query=Sarajedini%2C+A">Ata Sarajedini</a>, <a href="/search/astro-ph?searchtype=author&query=Woodley%2C+K">Kristin Woodley</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="1008.2755v2-abstract-short" style="display: inline;"> We present new measurements of the centers for 65 Milky Way globular clusters. Centers were determined by fitting ellipses to the density distribution within the inner $2\arcmin$ of the cluster center, and averaging the centers of these ellipses. The symmetry of clusters was also analyzed by comparing cumulative radial distributions on opposite sides of the cluster across a grid of trial centers.… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1008.2755v2-abstract-full').style.display = 'inline'; document.getElementById('1008.2755v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1008.2755v2-abstract-full" style="display: none;"> We present new measurements of the centers for 65 Milky Way globular clusters. Centers were determined by fitting ellipses to the density distribution within the inner $2\arcmin$ of the cluster center, and averaging the centers of these ellipses. The symmetry of clusters was also analyzed by comparing cumulative radial distributions on opposite sides of the cluster across a grid of trial centers. All of the determinations were done with stellar positions derived from a combination of two single-orbit ACS images of the core of the cluster in $F606W$ and $F814W$. We find that the ellipse-fitting method provides remarkable accuracy over a wide range of core sizes and density distributions, while the symmetry method is difficult to use on clusters with very large cores, or low density. The symmetry method requires a larger field, or a very sharply peaked density distribution. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1008.2755v2-abstract-full').style.display = 'none'; document.getElementById('1008.2755v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 August, 2010; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 16 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">17 pages, 8 figures, Accepted for publication in AJ, supplementary material will be available upon publication</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0911.0789">arXiv:0911.0789</a> <span> [<a href="https://arxiv.org/pdf/0911.0789">pdf</a>, <a href="https://arxiv.org/ps/0911.0789">ps</a>, <a href="https://arxiv.org/format/0911.0789">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1098/rsta.2009.0257">10.1098/rsta.2009.0257 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Star clusters as laboratories for stellar and dynamical evolution </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jason S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</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="0911.0789v1-abstract-short" style="display: inline;"> Open and globular star clusters have served as benchmarks for the study of stellar evolution due to their supposed nature as simple stellar populations of the same age and metallicity. After a brief review of some of the pioneering work that established the importance of imaging stars in these systems, we focus on several recent studies that have challenged our fundamental picture of star cluste… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0911.0789v1-abstract-full').style.display = 'inline'; document.getElementById('0911.0789v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0911.0789v1-abstract-full" style="display: none;"> Open and globular star clusters have served as benchmarks for the study of stellar evolution due to their supposed nature as simple stellar populations of the same age and metallicity. After a brief review of some of the pioneering work that established the importance of imaging stars in these systems, we focus on several recent studies that have challenged our fundamental picture of star clusters. These new studies indicate that star clusters can very well harbour multiple stellar populations, possibly formed through self-enrichment processes from the first-generation stars that evolved through post-main-sequence evolutionary phases. Correctly interpreting stellar evolution in such systems is tied to our understanding of both chemical-enrichment mechanisms, including stellar mass loss along the giant branches, and the dynamical state of the cluster. We illustrate recent imaging, spectroscopic and theoretical studies that have begun to shed new light on the evolutionary processes that occur within star clusters. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0911.0789v1-abstract-full').style.display = 'none'; document.getElementById('0911.0789v1-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, 2009; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2009. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">27 pages, 8 figures. To appear as invited review article in a special issue of the Phil. Trans. Royal Soc. A: Ch. 4 "Star clusters as tracers of galactic star-formation histories" (ed. R. de Grijs). Fully peer reviewed. LaTeX, requires rspublic.cls style file</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0909.2254">arXiv:0909.2254</a> <span> [<a href="https://arxiv.org/pdf/0909.2254">pdf</a>, <a href="https://arxiv.org/format/0909.2254">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/0004-637X/705/1/398">10.1088/0004-637X/705/1/398 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Spectral Types of White Dwarfs in Messier 4 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Davis%2C+D+S">D. Saul Davis</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Reitzel%2C+D+R">David R. Reitzel</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jason S. Kalirai</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="0909.2254v1-abstract-short" style="display: inline;"> We present the spectra of 24 white dwarfs in the direction of the globular cluster Messier 4 obtained with the Keck/LRIS and Gemini/GMOS spectrographs. Determining the spectral types of the stars in this sample, we find 24 type DA and 0 type DB (i.e., atmospheres dominated by hydrogen and helium respectively). Assuming the ratio of DA/DB observed in the field with effective temperature between 1… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0909.2254v1-abstract-full').style.display = 'inline'; document.getElementById('0909.2254v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0909.2254v1-abstract-full" style="display: none;"> We present the spectra of 24 white dwarfs in the direction of the globular cluster Messier 4 obtained with the Keck/LRIS and Gemini/GMOS spectrographs. Determining the spectral types of the stars in this sample, we find 24 type DA and 0 type DB (i.e., atmospheres dominated by hydrogen and helium respectively). Assuming the ratio of DA/DB observed in the field with effective temperature between 15,000 - 25,000 K, i.e., 4.2:1, holds for the cluster environment, the chance of finding no DBs in our sample due simply to statistical fluctuations is only 6 X 10^(-3). The spectral types of the ~100 white dwarfs previously identified in open clusters indicate that DB formation is strongly suppressed in that environment. Furthermore, all the ~10 white dwarfs previously identified in other globular clusters are exclusively type DA. In the context of these two facts, this finding suggests that DB formation is suppressed in the cluster environment in general. Though no satisfactory explanation for this phenomenon exists, we discuss several possibilities. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0909.2254v1-abstract-full').style.display = 'none'; document.getElementById('0909.2254v1-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 September, 2009; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2009. </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 Astrophys. J. 11 pages including 4 figures and 2 tables (journal format)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophys.J.705:398-407,2009 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0909.2253">arXiv:0909.2253</a> <span> [<a href="https://arxiv.org/pdf/0909.2253">pdf</a>, <a href="https://arxiv.org/ps/0909.2253">ps</a>, <a href="https://arxiv.org/format/0909.2253">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/0004-637X/705/1/408">10.1088/0004-637X/705/1/408 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Masses of Population II White Dwarfs </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jason S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Davis%2C+D+S">D. Saul Davis</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Bergeron%2C+P">P. Bergeron</a>, <a href="/search/astro-ph?searchtype=author&query=Catelan%2C+M">Marcio Catelan</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M+S">Brad M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</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="0909.2253v1-abstract-short" style="display: inline;"> Globular star clusters are among the first stellar populations to have formed in the Milky Way, and thus only a small sliver of their initial spectrum of stellar types are still burning hydrogen on the main-sequence today. Almost all of the stars born with more mass than 0.8 M_sun have evolved to form the white dwarf cooling sequence of these systems, and the distribution and properties of these… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0909.2253v1-abstract-full').style.display = 'inline'; document.getElementById('0909.2253v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0909.2253v1-abstract-full" style="display: none;"> Globular star clusters are among the first stellar populations to have formed in the Milky Way, and thus only a small sliver of their initial spectrum of stellar types are still burning hydrogen on the main-sequence today. Almost all of the stars born with more mass than 0.8 M_sun have evolved to form the white dwarf cooling sequence of these systems, and the distribution and properties of these remnants uniquely holds clues related to the nature of the now evolved progenitor stars. With ultra-deep HST imaging observations, rich white dwarf populations of four nearby Milky Way globular clusters have recently been uncovered, and are found to extend an impressive 5 - 8 magnitudes in the faint-blue region of the H-R diagram. In this paper, we characterize the properties of these population II remnants by presenting the first direct mass measurements of individual white dwarfs near the tip of the cooling sequence in the nearest of the Milky Way globulars, M4. Based on Gemini/GMOS and Keck/LRIS multiobject spectroscopic observations, our results indicate that 0.8 M_sun population II main-sequence stars evolving today form 0.53 +/- 0.01 M_sun white dwarfs. We discuss the implications of this result as it relates to our understanding of stellar structure and evolution of population II stars and for the age of the Galactic halo, as measured with white dwarf cooling theory. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0909.2253v1-abstract-full').style.display = 'none'; document.getElementById('0909.2253v1-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 September, 2009; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2009. </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 Astrophys. J. on Aug. 05th, 2009. 19 pages including 9 figures and 2 tables (journal format)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophys.J.705:408-425,2009 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0909.0398">arXiv:0909.0398</a> <span> [<a href="https://arxiv.org/pdf/0909.0398">pdf</a>, <a href="https://arxiv.org/ps/0909.0398">ps</a>, <a href="https://arxiv.org/format/0909.0398">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/nature08327">10.1038/nature08327 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The remnants of galaxy formation from a panoramic survey of the region around M31 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=McConnachie%2C+A+W">Alan W. McConnachie</a>, <a href="/search/astro-ph?searchtype=author&query=Irwin%2C+M+J">Michael J. Irwin</a>, <a href="/search/astro-ph?searchtype=author&query=Ibata%2C+R+A">Rodrigo A. Ibata</a>, <a href="/search/astro-ph?searchtype=author&query=Dubinski%2C+J">John Dubinski</a>, <a href="/search/astro-ph?searchtype=author&query=Widrow%2C+L+M">Lawrence M. Widrow</a>, <a href="/search/astro-ph?searchtype=author&query=Martin%2C+N+F">Nicolas F. Martin</a>, <a href="/search/astro-ph?searchtype=author&query=Cote%2C+P">Patrick Cote</a>, <a href="/search/astro-ph?searchtype=author&query=Dotter%2C+A+L">Aaron L. Dotter</a>, <a href="/search/astro-ph?searchtype=author&query=Navarro%2C+J+F">Julio F. Navarro</a>, <a href="/search/astro-ph?searchtype=author&query=Ferguson%2C+A+M+N">Annette M. N. Ferguson</a>, <a href="/search/astro-ph?searchtype=author&query=Puzia%2C+T+H">Thomas H. Puzia</a>, <a href="/search/astro-ph?searchtype=author&query=Lewis%2C+G+F">Geraint F. Lewis</a>, <a href="/search/astro-ph?searchtype=author&query=Babul%2C+A">Arif Babul</a>, <a href="/search/astro-ph?searchtype=author&query=Barmby%2C+P">Pauline Barmby</a>, <a href="/search/astro-ph?searchtype=author&query=Bienayme%2C+O">Olivier Bienayme</a>, <a href="/search/astro-ph?searchtype=author&query=Chapman%2C+S+C">Scott C. Chapman</a>, <a href="/search/astro-ph?searchtype=author&query=Cockcroft%2C+R">Robert Cockcroft</a>, <a href="/search/astro-ph?searchtype=author&query=Collins%2C+M+L+M">Michelle L. M. Collins</a>, <a href="/search/astro-ph?searchtype=author&query=Fardal%2C+M+A">Mark A. Fardal</a>, <a href="/search/astro-ph?searchtype=author&query=Harris%2C+W+E">William E. Harris</a>, <a href="/search/astro-ph?searchtype=author&query=Huxor%2C+A">Avon Huxor</a>, <a href="/search/astro-ph?searchtype=author&query=Mackey%2C+A+D">A. Dougal Mackey</a>, <a href="/search/astro-ph?searchtype=author&query=Penarrubia%2C+J">Jorge Penarrubia</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a> , et al. (4 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="0909.0398v1-abstract-short" style="display: inline;"> In hierarchical cosmological models, galaxies grow in mass through the continual accretion of smaller ones. The tidal disruption of these systems is expected to result in loosely bound stars surrounding the galaxy, at distances that reach $10 - 100$ times the radius of the central disk. The number, luminosity and morphology of the relics of this process provide significant clues to galaxy format… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0909.0398v1-abstract-full').style.display = 'inline'; document.getElementById('0909.0398v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0909.0398v1-abstract-full" style="display: none;"> In hierarchical cosmological models, galaxies grow in mass through the continual accretion of smaller ones. The tidal disruption of these systems is expected to result in loosely bound stars surrounding the galaxy, at distances that reach $10 - 100$ times the radius of the central disk. The number, luminosity and morphology of the relics of this process provide significant clues to galaxy formation history, but obtaining a comprehensive survey of these components is difficult because of their intrinsic faintness and vast extent. Here we report a panoramic survey of the Andromeda galaxy (M31). We detect stars and coherent structures that are almost certainly remnants of dwarf galaxies destroyed by the tidal field of M31. An improved census of their surviving counterparts implies that three-quarters of M31's satellites brighter than $M_V < -6$ await discovery. The brightest companion, Triangulum (M33), is surrounded by a stellar structure that provides persuasive evidence for a recent encounter with M31. This panorama of galaxy structure directly confirms the basic tenets of the hierarchical galaxy formation model and reveals the shared history of M31 and M33 in the unceasing build-up of galaxies. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0909.0398v1-abstract-full').style.display = 'none'; document.getElementById('0909.0398v1-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 September, 2009; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2009. </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">Published in Nature. Supplementary movie available at https://www.astrosci.ca/users/alan/PANDAS/Latest%20news%3A%20movie%20of%20orbit.html</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature 461:66-69,2009 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0902.1166">arXiv:0902.1166</a> <span> [<a href="https://arxiv.org/pdf/0902.1166">pdf</a>, <a href="https://arxiv.org/ps/0902.1166">ps</a>, <a href="https://arxiv.org/format/0902.1166">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/695/1/L20">10.1088/0004-637X/695/1/L20 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Dynamical Effects of White Dwarf Birth Kicks in Globular Star Clusters </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Fregeau%2C+J+M">John M. Fregeau</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Rasio%2C+F+A">Frederic A. Rasio</a>, <a href="/search/astro-ph?searchtype=author&query=Hurley%2C+J+R">Jarrod R. Hurley</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="0902.1166v2-abstract-short" style="display: inline;"> Recent observations of the white dwarf (WD) populations in the Galactic globular cluster NGC 6397 suggest that WDs receive a kick of a few km/s shortly before they are born. Using our Monte Carlo cluster evolution code, which includes accurate treatments of all relevant physical processes operating in globular clusters, we study the effects of the kicks on their host cluster and on the WD popula… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0902.1166v2-abstract-full').style.display = 'inline'; document.getElementById('0902.1166v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0902.1166v2-abstract-full" style="display: none;"> Recent observations of the white dwarf (WD) populations in the Galactic globular cluster NGC 6397 suggest that WDs receive a kick of a few km/s shortly before they are born. Using our Monte Carlo cluster evolution code, which includes accurate treatments of all relevant physical processes operating in globular clusters, we study the effects of the kicks on their host cluster and on the WD population itself. We find that in clusters whose velocity dispersion is comparable to the kick speed, WD kicks are a significant energy source for the cluster, prolonging the initial cluster core contraction phase significantly so that at late times the cluster core to half-mass radius ratio is a factor of up to ~ 10 larger than in the no-kick case. WD kicks thus represent a possible resolution of the large discrepancy between observed and theoretically predicted values of this key structural parameter. Our modeling also reproduces the observed trend for younger WDs to be more extended in their radial distribution in the cluster than older WDs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0902.1166v2-abstract-full').style.display = 'none'; document.getElementById('0902.1166v2-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 March, 2009; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 6 February, 2009; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2009. </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, accepted to ApJL; minor changes to reflect accepted 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/0807.0003">arXiv:0807.0003</a> <span> [<a href="https://arxiv.org/pdf/0807.0003">pdf</a>, <a href="https://arxiv.org/ps/0807.0003">ps</a>, <a href="https://arxiv.org/format/0807.0003">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1086/590660">10.1086/590660 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Glimpse into the Past: The Recent Evolution of Globular Clusters </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jasonjot S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Strader%2C+J">Jay Strader</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J">Jay Anderson</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="0807.0003v1-abstract-short" style="display: inline;"> We present the serendipitous discovery of 195 extragalactic globular clusters (GCs) in one of the deepest optical images ever obtained, a 126 orbit HST/ACS imaging study of the nearby Galactic GC NGC 6397. The distant GCs are all found surrounding a bright elliptical galaxy in the field, and are among the faintest objects detected in the image, with magnitudes 26 < F814W < 30. We measure the red… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0807.0003v1-abstract-full').style.display = 'inline'; document.getElementById('0807.0003v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0807.0003v1-abstract-full" style="display: none;"> We present the serendipitous discovery of 195 extragalactic globular clusters (GCs) in one of the deepest optical images ever obtained, a 126 orbit HST/ACS imaging study of the nearby Galactic GC NGC 6397. The distant GCs are all found surrounding a bright elliptical galaxy in the field, and are among the faintest objects detected in the image, with magnitudes 26 < F814W < 30. We measure the redshift of the parent elliptical galaxy, using GMOS on Gemini South, to be z = 0.089 (375 Mpc). This galaxy, and its associated clusters, therefore ranks as one of the most distant such systems discovered to date. The measured light from these clusters was emitted 1.2 Gyr ago (the lookback time) and therefore the optical properties hold clues for understanding the evolution of GCs over the past Gyr. We measure the color function of the bright GCs and find that both a blue and red population exist, and that the colors of each sub-population are redder than GCs in local elliptical galaxies of comparable luminosity. For the blue clusters, the observed color difference from z = 0.089 to today is only slightly larger than predictions from stellar evolution (e.g., changes in the luminosity and color of the main-sequence turnoff and the morphology of the horizontal branch). A larger color difference is found in the red clusters, possibly suggesting that they are very metal-rich and/or significantly younger than 12 Gyr. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0807.0003v1-abstract-full').style.display = 'none'; document.getElementById('0807.0003v1-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 June, 2008; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2008. </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, 2 figures. Accepted for publication in ApJ Letters. Higher resolution Figure 1 available at http://www.ucolick.org/~jkalirai/DistantGlobs/</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0803.0740">arXiv:0803.0740</a> <span> [<a href="https://arxiv.org/pdf/0803.0740">pdf</a>, <a href="https://arxiv.org/ps/0803.0740">ps</a>, <a href="https://arxiv.org/format/0803.0740">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/0004-6256/135/6/2114">10.1088/0004-6256/135/6/2114 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Deep HST Study of the Globular Cluster NGC 6397: Reduction Methods </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J">Jay Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=King%2C+I+R">Ivan R. King</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">Gregory G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M+S">Brad M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Hurley%2C+J">Jarrod Hurley</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jasonjot S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Stetson%2C+P+B">Peter B. Stetson</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="0803.0740v1-abstract-short" style="display: inline;"> We describe here the reduction methods that we developed to study the faintest red dwarfs and white dwarfs in an outer field of NGC6397, which was observed by \hst for 126 orbits in 2005. The particular challenge of this data set is that the faintest stars are not readily visible in individual exposures, so special care must be taken to combine the information in all the exposures in order to id… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0803.0740v1-abstract-full').style.display = 'inline'; document.getElementById('0803.0740v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0803.0740v1-abstract-full" style="display: none;"> We describe here the reduction methods that we developed to study the faintest red dwarfs and white dwarfs in an outer field of NGC6397, which was observed by \hst for 126 orbits in 2005. The particular challenge of this data set is that the faintest stars are not readily visible in individual exposures, so special care must be taken to combine the information in all the exposures in order to identify and measure them. Unfortunately, it is hard to find the faintest stars without also finding a large number of faint galaxies, so we developed specialized tools to distinguish between the point-like stars and the barely resolved galaxies. We found that artificial-star tests, while obviously necessary for completeness determination, can also play an important role in helping us optimize our finding and measuring algorithms. Although this paper focuses on this data set specifically, many of the techniques are new and might find application in other work, particularly when a large number of images is available for a single field. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0803.0740v1-abstract-full').style.display = 'none'; document.getElementById('0803.0740v1-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 March, 2008; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2008. </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">35 pages, preprint style</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0803.0005">arXiv:0803.0005</a> <span> [<a href="https://arxiv.org/pdf/0803.0005">pdf</a>, <a href="https://arxiv.org/ps/0803.0005">ps</a>, <a href="https://arxiv.org/format/0803.0005">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/0004-6256/135/6/2155">10.1088/0004-6256/135/6/2155 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The binary fraction in the globular cluster NGC 6397 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Davis%2C+D+S">D. S. Davis</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">H. B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J">J. Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=Brewer%2C+J+P">J. P. Brewer</a>, <a href="/search/astro-ph?searchtype=author&query=Hurley%2C+J">J. Hurley</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">J. S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. M. Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Stetson%2C+P+B">P. B. Stetson</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="0803.0005v2-abstract-short" style="display: inline;"> Using Hubble Space Telescope (HST) observations of the globular cluster NGC6397, we constrain the cluster's binary fraction. The observations consist of two fields: the primary science field, a single ACS pointing centered approximately 5' from the cluster center; and the parallel field, a single WFPC2 field centered on the cluster center. Using the exquisite photometric precision of these obser… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0803.0005v2-abstract-full').style.display = 'inline'; document.getElementById('0803.0005v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0803.0005v2-abstract-full" style="display: none;"> Using Hubble Space Telescope (HST) observations of the globular cluster NGC6397, we constrain the cluster's binary fraction. The observations consist of two fields: the primary science field, a single ACS pointing centered approximately 5' from the cluster center; and the parallel field, a single WFPC2 field centered on the cluster center. Using the exquisite photometric precision of these observations, we determine the binary fraction in these regions of the cluster by examining stars lying off the main sequence. The binary fraction is constrained to be 0.012 +/- 0.004 in the ACS field, and to be 0.051 +/- 0.010 in the WFPC field. N-body simulations by Hurley et al. (2007) suggest that the binary fraction remains nearly constant beyond the half-mass radius for the lifetime of the cluster. In the context of these simulations, our results suggest that NGC 6397 had a primordial binary fraction of only ~1%. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0803.0005v2-abstract-full').style.display = 'none'; document.getElementById('0803.0005v2-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 March, 2008; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 29 February, 2008; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2008. </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, 7 figures, accepted in AJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0802.4127">arXiv:0802.4127</a> <span> [<a href="https://arxiv.org/pdf/0802.4127">pdf</a>, <a href="https://arxiv.org/ps/0802.4127">ps</a>, <a href="https://arxiv.org/format/0802.4127">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/0004-6256/135/6/2129">10.1088/0004-6256/135/6/2129 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Deep ACS Imaging in the Globular Cluster NGC6397: Dynamical Models </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Hurley%2C+J+R">Jarrod R. Hurley</a>, <a href="/search/astro-ph?searchtype=author&query=Shara%2C+M+M">Michael M. Shara</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=King%2C+I+R">Ivan R. King</a>, <a href="/search/astro-ph?searchtype=author&query=Davis%2C+D+S">D. Saul Davis</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jason S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M+S">Brad M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Dotter%2C+A">Aaron Dotter</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J">Jay Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">Gregory G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</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="0802.4127v1-abstract-short" style="display: inline;"> We present N-body models to complement deep imaging of the metal-poor core-collapsed cluster NGC6397 obtained with the Hubble Space Telescope. All simulations include stellar and binary evolution in-step with the stellar dynamics and account for the tidal field of the Galaxy. We focus on the results of a simulation that began with 100000 objects (stars and binaries), 5% primordial binaries and P… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0802.4127v1-abstract-full').style.display = 'inline'; document.getElementById('0802.4127v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0802.4127v1-abstract-full" style="display: none;"> We present N-body models to complement deep imaging of the metal-poor core-collapsed cluster NGC6397 obtained with the Hubble Space Telescope. All simulations include stellar and binary evolution in-step with the stellar dynamics and account for the tidal field of the Galaxy. We focus on the results of a simulation that began with 100000 objects (stars and binaries), 5% primordial binaries and Population II metallicity. After 16 Gyr of evolution the model cluster has about 20% of the stars remaining and has reached core-collapse. We compare the color-magnitude diagrams of the model at this age for the central region and an outer region corresponding to the observed field of NGC6397 (about 2-3 half-light radii from the cluster centre). This demonstrates that the white dwarf population in the outer region has suffered little modification from dynamical processes - contamination of the luminosity function by binaries and white dwarfs with non-standard evolution histories is minimal and should not significantly affect measurement of the cluster age. We also show that the binary fraction of main-sequence stars observed in the NGC6397 field can be taken as representative of the primordial binary fraction of the cluster. For the mass function of the main-sequence stars we find that although this has been altered significantly by dynamics over the cluster lifetime, especially in the central and outer regions, that the position of the observed field is close to optimal for recovering the initial mass function of the cluster stars (below the current turn-off mass). More generally we look at how the mass function changes with radius in a dynamically evolved stellar cluster and suggest where the best radial position to observe the initial mass function is for clusters of any age. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0802.4127v1-abstract-full').style.display = 'none'; document.getElementById('0802.4127v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 28 February, 2008; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2008. </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">34 pages, 11 figures, submitted to AJ, companion paper to 0708.4030</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0709.4286">arXiv:0709.4286</a> <span> [<a href="https://arxiv.org/pdf/0709.4286">pdf</a>, <a href="https://arxiv.org/ps/0709.4286">ps</a>, <a href="https://arxiv.org/format/0709.4286">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1111/j.1745-3933.2007.00402.x">10.1111/j.1745-3933.2007.00402.x <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> On the Radial Distribution of White Dwarfs in the Globular Cluster NGC 6397 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Davis%2C+D+S">D. S. Davis</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">H. B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=King%2C+I+R">I. R. King</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J">J. Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=Coffey%2C+J">J. Coffey</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">G. G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Hurley%2C+J">J. Hurley</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">J. S. Kalirai</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="0709.4286v1-abstract-short" style="display: inline;"> We have examined the radial distribution of white dwarfs over a single HST/ACS field in the nearby globular cluster NGC 6397. In relaxed populations, such as in a globular cluster, stellar velocity dispersion, and hence radial distribution, is directly dependent on stellar masses. The progenitors of very young cluster white dwarfs had a mass of ~0.8 solar masses, while the white dwarfs themselve… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0709.4286v1-abstract-full').style.display = 'inline'; document.getElementById('0709.4286v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0709.4286v1-abstract-full" style="display: none;"> We have examined the radial distribution of white dwarfs over a single HST/ACS field in the nearby globular cluster NGC 6397. In relaxed populations, such as in a globular cluster, stellar velocity dispersion, and hence radial distribution, is directly dependent on stellar masses. The progenitors of very young cluster white dwarfs had a mass of ~0.8 solar masses, while the white dwarfs themselves have a mass of ~0.5 solar masses. We thus expect young white dwarfs to have a concentrated radial distribution (like that of their progenitors) that becomes more extended over several relaxation times to mimic that of ~0.5 solar mass main-sequence stars. However, we observe young white dwarfs to have a significantly extended radial distribution compared to both the most massive main sequence stars in the cluster and also to old white dwarfs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0709.4286v1-abstract-full').style.display = 'none'; document.getElementById('0709.4286v1-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 September, 2007; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2007. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">13 pages including 1 table and 3 figures. Accepted for publication in the MNRAS 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/0708.4030">arXiv:0708.4030</a> <span> [<a href="https://arxiv.org/pdf/0708.4030">pdf</a>, <a href="https://arxiv.org/ps/0708.4030">ps</a>, <a href="https://arxiv.org/format/0708.4030">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/0004-6256/135/6/2141">10.1088/0004-6256/135/6/2141 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Deep ACS Imaging in the Globular Cluster NGC 6397: The Cluster Color Magnitude Diagram and Luminosity Function </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Dotter%2C+A">Aaron Dotter</a>, <a href="/search/astro-ph?searchtype=author&query=Hurley%2C+J">Jarrod Hurley</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J">Jay Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=King%2C+I">Ivan King</a>, <a href="/search/astro-ph?searchtype=author&query=Davis%2C+S">Saul Davis</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">Gregory G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M+S">Brad M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J">Jason Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Paust%2C+N">Nathaniel Paust</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Shara%2C+M+M">Michael M. Shara</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="0708.4030v1-abstract-short" style="display: inline;"> We present the CMD from deep HST imaging in the globular cluster NGC 6397. The ACS was used for 126 orbits to image a single field in two colors (F814W, F606W) 5 arcmin SE of the cluster center. The field observed overlaps that of archival WFPC2 data from 1994 and 1997 which were used to proper motion (PM) clean the data. Applying the PM corrections produces a remarkably clean CMD which reveals… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0708.4030v1-abstract-full').style.display = 'inline'; document.getElementById('0708.4030v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0708.4030v1-abstract-full" style="display: none;"> We present the CMD from deep HST imaging in the globular cluster NGC 6397. The ACS was used for 126 orbits to image a single field in two colors (F814W, F606W) 5 arcmin SE of the cluster center. The field observed overlaps that of archival WFPC2 data from 1994 and 1997 which were used to proper motion (PM) clean the data. Applying the PM corrections produces a remarkably clean CMD which reveals a number of features never seen before in a globular cluster CMD. In our field, the main sequence stars appeared to terminate close to the location in the CMD of the hydrogen-burning limit predicted by two independent sets of stellar evolution models. The faintest observed main sequence stars are about a magnitude fainter than the least luminous metal-poor field halo stars known, suggesting that the lowest luminosity halo stars still await discovery. At the bright end the data extend beyond the main sequence turnoff to well up the giant branch. A populous white dwarf cooling sequence is also seen in the cluster CMD. The most dramatic features of the cooling sequence are its turn to the blue at faint magnitudes as well as an apparent truncation near F814W = 28. The cluster luminosity and mass functions were derived, stretching from the turn off down to the hydrogen-burning limit. It was well modeled with either a very flat power-law or a lognormal function. In order to interpret these fits more fully we compared them with similar functions in the cluster core and with a full N-body model of NGC 6397 finding satisfactory agreement between the model predictions and the data. This exercise demonstrates the important role and the effect that dynamics has played in altering the cluster IMF. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0708.4030v1-abstract-full').style.display = 'none'; document.getElementById('0708.4030v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 29 August, 2007; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2007. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">43 pages including 4 tables and 12 diagrams. Figures 2 and 3 have been bitmapped. Accepted for publication in the Astronomical Journal</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0706.3894">arXiv:0706.3894</a> <span> [<a href="https://arxiv.org/pdf/0706.3894">pdf</a>, <a href="https://arxiv.org/ps/0706.3894">ps</a>, <a href="https://arxiv.org/format/0706.3894">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1086/527028">10.1086/527028 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Initial-Final Mass Relation: Direct Constraints at the Low Mass End </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jasonjot S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M+S">Brad M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Kelson%2C+D+D">Daniel D. Kelson</a>, <a href="/search/astro-ph?searchtype=author&query=Reitzel%2C+D+B">David B. Reitzel</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</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="0706.3894v2-abstract-short" style="display: inline;"> The initial-final mass relation represents a mapping between the mass of a white dwarf remnant and the mass that the hydrogen burning main-sequence star that created it once had. The relation thus far has been constrained using a sample of ~40 stars in young open clusters, ranging in initial mass from ~2.75 -- 7 Msun, and shows a general trend that connects higher mass main-sequence stars with h… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0706.3894v2-abstract-full').style.display = 'inline'; document.getElementById('0706.3894v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0706.3894v2-abstract-full" style="display: none;"> The initial-final mass relation represents a mapping between the mass of a white dwarf remnant and the mass that the hydrogen burning main-sequence star that created it once had. The relation thus far has been constrained using a sample of ~40 stars in young open clusters, ranging in initial mass from ~2.75 -- 7 Msun, and shows a general trend that connects higher mass main-sequence stars with higher mass white dwarfs. In this paper, we present CFHT/CFH12K photometric and Keck/LRIS multiobject spectroscopic observations of a sample of 22 white dwarfs in two older open clusters, NGC 7789 (t = 1.4 Gyr) and NGC 6819 (t = 2.5 Gyr). We measure masses for the highest S/N spectra by fitting the Balmer lines to atmosphere models and place the first direct constraints on the low mass end of the initial-final mass relation. Our results indicate that the observed general trend at higher masses continues down to low masses, with M_initial = 1.16 Msun main-sequence stars forming M_final = 0.53 Msun white dwarfs (including our data from the very old open cluster, NGC 6791). This extention of the relation represents a four fold increase in the total number of hydrogen burning stars for which the integrated mass loss can now be calculated, assuming a Salpeter initial mass function. The new leverage at the low mass end is used to derive a purely empirical initial-final mass relation without the need for any indirectly derived anchor points. The sample of white dwarfs in these clusters also shows several very interesting systems that we discuss further: a DB (helium atmosphere) white dwarf, a magnetic white dwarf, a DAB (mixed hydrogen/helium atmosphere or a double degenerate DA+DB) white dwarf(s), and two possible equal mass DA double degenerate binary systems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0706.3894v2-abstract-full').style.display = 'none'; document.getElementById('0706.3894v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 October, 2007; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 27 June, 2007; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2007. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">18 pages, 12 figures, 3 tables. Submitted to Astrophys. J. Revised from first version</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophys.J. 676 (2008) 594 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0705.0977">arXiv:0705.0977</a> <span> [<a href="https://arxiv.org/pdf/0705.0977">pdf</a>, <a href="https://arxiv.org/ps/0705.0977">ps</a>, <a href="https://arxiv.org/format/0705.0977">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1086/521922">10.1086/521922 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Stellar Evolution in NGC 6791: Mass Loss on the Red Giant Branch and the Formation of Low Mass White Dwarfs </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jasonjot S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Bergeron%2C+P">P. Bergeron</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M+S">Brad M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Kelson%2C+D+D">Daniel D. Kelson</a>, <a href="/search/astro-ph?searchtype=author&query=Reitzel%2C+D+B">David B. Reitzel</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</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="0705.0977v3-abstract-short" style="display: inline;"> We present the first detailed study of the properties (temperatures, gravities, and masses) of the NGC 6791 white dwarf population. This unique stellar system is both one of the oldest (8 Gyr) and most metal-rich ([Fe/H] ~ 0.4) open clusters in our Galaxy, and has a color-magnitude diagram (CMD) that exhibits both a red giant clump and a much hotter extreme horizontal branch. Fitting the Balmer… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0705.0977v3-abstract-full').style.display = 'inline'; document.getElementById('0705.0977v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0705.0977v3-abstract-full" style="display: none;"> We present the first detailed study of the properties (temperatures, gravities, and masses) of the NGC 6791 white dwarf population. This unique stellar system is both one of the oldest (8 Gyr) and most metal-rich ([Fe/H] ~ 0.4) open clusters in our Galaxy, and has a color-magnitude diagram (CMD) that exhibits both a red giant clump and a much hotter extreme horizontal branch. Fitting the Balmer lines of the white dwarfs in the cluster, using Keck/LRIS spectra, suggests that most of these stars are undermassive, <M> = 0.43 +/- 0.06 Msun, and therefore could not have formed from canonical stellar evolution involving the helium flash at the tip of the red giant branch. We show that at least 40% of NGC 6791's evolved stars must have lost enough mass on the red giant branch to avoid the flash, and therefore did not convert helium into carbon-oxygen in their core. Such increased mass loss in the evolution of the progenitors of these stars is consistent with the presence of the extreme horizontal branch in the CMD. This unique stellar evolutionary channel also naturally explains the recent finding of a very young age (2.4 Gyr) for NGC 6791 from white dwarf cooling theory; helium core white dwarfs in this cluster will cool ~3 times slower than carbon-oxygen core stars and therefore the corrected white dwarf cooling age is in fact ~7 Gyr, consistent with the well measured main-sequence turnoff age. These results provide direct empirical evidence that mass loss is much more efficient in high metallicity environments and therefore may be critical in interpreting the ultraviolet upturn in elliptical galaxies. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0705.0977v3-abstract-full').style.display = 'none'; document.getElementById('0705.0977v3-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 October, 2007; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 7 May, 2007; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2007. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">15 pages, 9 figures, 2 tables. Accepted for publication in Astrophys. J. Very minor changes from first version</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophys.J.671:748-760,2007 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0702209">arXiv:astro-ph/0702209</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0702209">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1126/science.1130691">10.1126/science.1130691 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Probing the Faintest Stars in a Globular Star Cluster </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J">Jay Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=Brewer%2C+J">James Brewer</a>, <a href="/search/astro-ph?searchtype=author&query=Davis%2C+S">Saul Davis</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">Gregory G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M+S">Brad M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Hurley%2C+J">Jarrod Hurley</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jasonjot S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=King%2C+I+R">Ivan R. King</a>, <a href="/search/astro-ph?searchtype=author&query=Reitzel%2C+D">David Reitzel</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Shara%2C+M+M">Michael M. Shara</a>, <a href="/search/astro-ph?searchtype=author&query=Stetson%2C+P+B">Peter B. Stetson</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0702209v1-abstract-short" style="display: inline;"> NGC 6397 is the second closest globular star cluster to the Sun. Using 5 days of time on the Hubble Space Telescope, we have constructed the deepest ever color-magnitude diagram for this cluster. We see a clear truncation in each of its two major stellar sequences. Faint red main sequence stars run out well above our observational limit and near to the theoretical prediction for the lowest mass… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0702209v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0702209v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0702209v1-abstract-full" style="display: none;"> NGC 6397 is the second closest globular star cluster to the Sun. Using 5 days of time on the Hubble Space Telescope, we have constructed the deepest ever color-magnitude diagram for this cluster. We see a clear truncation in each of its two major stellar sequences. Faint red main sequence stars run out well above our observational limit and near to the theoretical prediction for the lowest mass stars capable of stable hydrogen-burning in their cores. We also see a truncation in the number counts of faint blue stars, namely white dwarfs. This reflects the limit to which the bulk of the white dwarfs can cool over the lifetime of the cluster. There is also a turn towards bluer colors in the least luminous of these objects. This was predicted for the very coolest white dwarfs with hydrogen-rich atmospheres as the formation of H2 causes their atmospheres to become largely opaque to infrared radiation due to collision-induced absorption. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0702209v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0702209v1-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 February, 2007; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2007. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">12 pages, 4 figures. Full Resolution Figures in Science, 2006, 313, 936</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Science313:936,2006 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0701781">arXiv:astro-ph/0701781</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0701781">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0701781">ps</a>, <a href="https://arxiv.org/format/astro-ph/0701781">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1086/513102">10.1086/513102 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Space Motion of the Globular Cluster NGC 6397 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jasonjot S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J">Jay Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=King%2C+I+R">Ivan R. King</a>, <a href="/search/astro-ph?searchtype=author&query=Brewer%2C+J+P">James P. Brewer</a>, <a href="/search/astro-ph?searchtype=author&query=Carraro%2C+G">Giovanni Carraro</a>, <a href="/search/astro-ph?searchtype=author&query=Davis%2C+S+D">Saul D. Davis</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">Gregory G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M+S">Brad M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Hurley%2C+J+R">Jarrod R. Hurley</a>, <a href="/search/astro-ph?searchtype=author&query=Lepine%2C+S">Sebastien Lepine</a>, <a href="/search/astro-ph?searchtype=author&query=Reitzel%2C+D+B">David B. Reitzel</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Shara%2C+M+M">Michael M. Shara</a>, <a href="/search/astro-ph?searchtype=author&query=Stetson%2C+P+B">Peter B. Stetson</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0701781v2-abstract-short" style="display: inline;"> As a by-product of high-precision, ultra-deep stellar photometry in the Galactic globular cluster NGC 6397 with the Hubble Space Telescope, we are able to measure a large population of background galaxies whose images are nearly point-like. These provide an extragalactic reference frame of unprecedented accuracy, relative to which we measure the most accurate absolute proper motion ever determin… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0701781v2-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0701781v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0701781v2-abstract-full" style="display: none;"> As a by-product of high-precision, ultra-deep stellar photometry in the Galactic globular cluster NGC 6397 with the Hubble Space Telescope, we are able to measure a large population of background galaxies whose images are nearly point-like. These provide an extragalactic reference frame of unprecedented accuracy, relative to which we measure the most accurate absolute proper motion ever determined for a globular cluster. We find mu_alpha = 3.56 +/- 0.04 mas/yr and mu_delta = -17.34 +/- 0.04 mas/yr. We note that the formal statistical errors quoted for the proper motion of NGC 6397 do not include possible unavoidable sources of systematic errors, such as cluster rotation. These are very unlikely to exceed a few percent. We use this new proper motion to calculate NGC 6397's UVW space velocity and its orbit around the Milky Way, and find that the cluster has made frequent passages through the Galactic disk. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0701781v2-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0701781v2-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 February, 2007; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 26 January, 2007; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2007. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">5 pages including 3 figures, accepted for publication in the Astrophysical Journal Letters. Very minor changes in V2. typos fixed</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophys.J.Lett.657:L93-L96,2007 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0701738">arXiv:astro-ph/0701738</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0701738">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0701738">ps</a>, <a href="https://arxiv.org/format/astro-ph/0701738">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1086/522567">10.1086/522567 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The White Dwarf Cooling Sequence of NGC6397 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M+S">Brad M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J">Jay Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=Brewer%2C+J">James Brewer</a>, <a href="/search/astro-ph?searchtype=author&query=Dotter%2C+A">Aaron Dotter</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">Greg. G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Hurley%2C+J">Jarrod Hurley</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J">Jason Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=King%2C+I">Ivan King</a>, <a href="/search/astro-ph?searchtype=author&query=Reitzel%2C+D">David Reitzel</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Shara%2C+M+M">Michael M. Shara</a>, <a href="/search/astro-ph?searchtype=author&query=Stetson%2C+P+B">Peter B. Stetson</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0701738v2-abstract-short" style="display: inline;"> We present the results of a deep Hubble Space Telescope (HST) exposure of the nearby globular cluster NGC6397, focussing attention on the cluster's white dwarf cooling sequence. This sequence is shown to extend over 5 magnitudes in depth, with an apparent cutoff at magnitude F814W=27.6. We demonstrate, using both artificial star tests and the detectability of background galaxies at fainter magni… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0701738v2-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0701738v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0701738v2-abstract-full" style="display: none;"> We present the results of a deep Hubble Space Telescope (HST) exposure of the nearby globular cluster NGC6397, focussing attention on the cluster's white dwarf cooling sequence. This sequence is shown to extend over 5 magnitudes in depth, with an apparent cutoff at magnitude F814W=27.6. We demonstrate, using both artificial star tests and the detectability of background galaxies at fainter magnitudes, that the cutoff is real and represents the truncation of the white dwarf luminosity function in this cluster. We perform a detailed comparison between cooling models and the observed distribution of white dwarfs in colour and magnitude, taking into account uncertainties in distance, extinction, white dwarf mass, progenitor lifetimes, binarity and cooling model uncertainties. After marginalising over these variables, we obtain values for the cluster distance modulus and age of 渭_0 = 12.02 \pm 0.06 and T_c = 11.47 \pm 0.47Gyr (95% confidence limits). Our inferred distance and white dwarf initial-final mass relations are in good agreement with other independent determinations, and the cluster age is consistent with, but more precise than, prior determinations made using the main sequence turnoff method. In particular, within the context of the currently accepted 螞CDM cosmological model, this age places the formation of NGC6397 at a redshift z=3, at a time when the cosmological star formation rate was approaching its peak. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0701738v2-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0701738v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 20 February, 2007; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 January, 2007; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2007. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">56 pages, 30 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/astro-ph/0411095">arXiv:astro-ph/0411095</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0411095">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0411095">ps</a>, <a href="https://arxiv.org/format/astro-ph/0411095">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1086/427247">10.1086/427247 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Carbon Stars and other Luminous Stellar Populations in M33 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Rowe%2C+J+F">J. F. Rowe</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">H. B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Brewer%2C+J+P">J. P. Brewer</a>, <a href="/search/astro-ph?searchtype=author&query=Crabtree%2C+D+R">D. R. Crabtree</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0411095v1-abstract-short" style="display: inline;"> The M33 galaxy is a nearby, relatively metal-poor, late-type spiral. Its proximity and almost face-on inclination means that it projects over a large area on the sky, making it an ideal candidate for wide-field CCD mosaic imaging. Photometry was obtained for more than 10^6 stars covering a 74' x 56' field centered on M33. Main sequence (MS), supergiant branch (SGB), red giant branch (RGB) and as… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0411095v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0411095v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0411095v1-abstract-full" style="display: none;"> The M33 galaxy is a nearby, relatively metal-poor, late-type spiral. Its proximity and almost face-on inclination means that it projects over a large area on the sky, making it an ideal candidate for wide-field CCD mosaic imaging. Photometry was obtained for more than 10^6 stars covering a 74' x 56' field centered on M33. Main sequence (MS), supergiant branch (SGB), red giant branch (RGB) and asymptotic giant branch (AGB) populations are identified and classified based on broad-band V and I photometry. Narrow-band filters are used to measure spectral features allowing the AGB population to be further divided into C and M-star types. The galactic structure of M33 is examined using star counts, colour-colour and colour-magnitude selected stellar populations. We use the C to M-star ratio to investigate the metallicity gradient in the disk of M33. The C/M-star ratio is found to increase and then flatten with increasing galactocentric radius in agreement with viscous disk formation models. The C-star luminosity function is found to be similar to M31 and the SMC, suggesting that C-stars should be useful distance indicators. The ``spectacular arcs of carbon stars'' in M33 postulated recently by Block et al. (2004) are found in our work to be simply an extension of M33's disk. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0411095v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0411095v1-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 November, 2004; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2004. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">20 pages, 20 figures. Accepted for publication in The Astronomical Journal</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0409172">arXiv:astro-ph/0409172</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0409172">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0409172">ps</a>, <a href="https://arxiv.org/format/astro-ph/0409172">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> </div> <p class="title is-5 mathjax"> The Dearth of Massive, Helium-Rich White Dwarfs in Young Open Star Clusters </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jasonjot Singh Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M+S">Brad M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Reitzel%2C+D">David Reitzel</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0409172v3-abstract-short" style="display: inline;"> Spectra have been obtained of 21 white dwarfs (WDs) in the direction of the young, rich open star cluster NGC 2099. This represents an appreciable fraction (>30%) of the cluster's total WD population. The mean derived mass of the sample is 0.8 Msun - about 0.2 Msun larger than the mean seen among field WDs. A surprising result is that all of the NGC 2099 WDs have hydrogen-rich atmospheres (DAs)… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0409172v3-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0409172v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0409172v3-abstract-full" style="display: none;"> Spectra have been obtained of 21 white dwarfs (WDs) in the direction of the young, rich open star cluster NGC 2099. This represents an appreciable fraction (>30%) of the cluster's total WD population. The mean derived mass of the sample is 0.8 Msun - about 0.2 Msun larger than the mean seen among field WDs. A surprising result is that all of the NGC 2099 WDs have hydrogen-rich atmospheres (DAs) and none exhibit helium-rich ones (DBs), or any other spectral class. The number ratio in the field at the temperatures of the NGC 2099 WDs is DA/DB ~ 3.5. While the probability of seeing no DB WDs in NGC 2099 solely by chance is ~2%, if we include WDs in other open clusters of similar age it then becomes highly unlikely that the dearth of DB WDs in young open clusters is just a statistical fluctuation. We explore possible reasons for the lack of DBs in these clusters and conclude that the most promising scenario for the DA/DB number ratio discrepancy in young clusters is that hot, high-mass WDs do not develop large enough helium convection zones to allow helium to be brought to the surface and turn a hydrogen-rich WD into a helium-rich one. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0409172v3-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0409172v3-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 December, 2004; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 7 September, 2004; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2004. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">4 pages including 1 figure and 1 table, accepted in ApJ Letters. References added and discussion expanded in Section 5</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophys.J. 618 (2004) L129-L132 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0409171">arXiv:astro-ph/0409171</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0409171">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0409171">ps</a>, <a href="https://arxiv.org/format/astro-ph/0409171">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> </div> <p class="title is-5 mathjax"> The Initial-Final Mass Relationship: Spectroscopy of White Dwarfs in NGC 2099 (M37) </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jasonjot Singh Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Reitzel%2C+D">David Reitzel</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M+S">Brad M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">Gregory G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Gibson%2C+B+K">Brad K. Gibson</a>, <a href="/search/astro-ph?searchtype=author&query=von+Hippel%2C+T">Ted von Hippel</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0409171v3-abstract-short" style="display: inline;"> We present new observations of very faint white dwarfs (WDs) in the rich open star cluster NGC 2099 (M37). Following deep, wide field imaging of the cluster using CFHT, we have now obtained spectroscopic observations of candidate WDs using both GMOS on Gemini and LRIS on Keck. Of our 24 WD candidates (all fainter than V = 22.4), 21 are spectroscopically confirmed to be bona fide WDs, 4-5 of whic… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0409171v3-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0409171v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0409171v3-abstract-full" style="display: none;"> We present new observations of very faint white dwarfs (WDs) in the rich open star cluster NGC 2099 (M37). Following deep, wide field imaging of the cluster using CFHT, we have now obtained spectroscopic observations of candidate WDs using both GMOS on Gemini and LRIS on Keck. Of our 24 WD candidates (all fainter than V = 22.4), 21 are spectroscopically confirmed to be bona fide WDs, 4-5 of which are most likely field objects. Fitting 18 of the 21 WD spectra with model atmospheres, we find that most WDs in this cluster are quite massive (0.7-0.9 Msun), as expected given the cluster's young age (650 Myr) and, hence, high turnoff mass (~2.4 Msun). We determine a new initial-final mass relationship and almost double the number of existing data points from previous studies. The results indicate that stars with initial masses between 2.8 and 3.4 Msun lose 70-75% of their mass through stellar evolution. For the first time, we find some evidence of a metallicity dependence on the initial-final mass relationship. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0409171v3-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0409171v3-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 December, 2004; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 7 September, 2004; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2004. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">5 pages including 3 figures and 1 table, accepted in ApJ Letters. Minor additions to content and typos corrected</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophys.J. 618 (2004) L123-L128 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0401446">arXiv:astro-ph/0401446</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0401446">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0401446">ps</a>, <a href="https://arxiv.org/format/astro-ph/0401446">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1086/383294">10.1086/383294 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Concerning the White Dwarf Cooling Age of M4: A Response to the Paper by De Marchi et al. on "A Different Interpretation of Recent HST Observations" </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">H. B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Brewer%2C+J">J. Brewer</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">G. G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J">J. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Stetson%2C+P+B">P. B. Stetson</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M+S">B. M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. M. Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Ibata%2C+R+A">R. A. Ibata</a>, <a href="/search/astro-ph?searchtype=author&query=Gibson%2C+B+K">B. K. Gibson</a>, <a href="/search/astro-ph?searchtype=author&query=Shara%2C+M">M. Shara</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0401446v1-abstract-short" style="display: inline;"> We respond to the paper by De Marchi, Paresce, Straniero and Moroni (2003) on the white dwarf cooling age of M4. The authors question the data analysis and interpretation that led to the conclusions in Hansen et al. (2002). In their paper, De Marchi et al. are unable to obtain photometry as deep as ours from the same data set and therefore assert that only a lower limit to the white dwarf coolin… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0401446v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0401446v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0401446v1-abstract-full" style="display: none;"> We respond to the paper by De Marchi, Paresce, Straniero and Moroni (2003) on the white dwarf cooling age of M4. The authors question the data analysis and interpretation that led to the conclusions in Hansen et al. (2002). In their paper, De Marchi et al. are unable to obtain photometry as deep as ours from the same data set and therefore assert that only a lower limit to the white dwarf cooling age for this cluster of approximately 9 Gyr can be obtained. In this short contribution we show that shortcomings in the data analysis and reduction techniques of De Marchi et al. are responsible for their inability to reach the photometry limits that our study reports. In a forthcoming paper in which the complete techniques for age determination with white dwarfs are laid out, we demonstrate that their method of fitting the luminosity function gives a spuriously low white dwarf cooling age. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0401446v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0401446v1-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 January, 2004; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2004. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">14 pages, 5 figures, AJ 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/astro-ph/0401440">arXiv:astro-ph/0401440</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0401440">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0401440">ps</a>, <a href="https://arxiv.org/format/astro-ph/0401440">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> </div> <p class="title is-5 mathjax"> HST Observations of the Main Sequence of M4 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">H. B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">G. G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Brewer%2C+J">J. Brewer</a>, <a href="/search/astro-ph?searchtype=author&query=Davis%2C+S">S. Davis</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J">J. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Stetson%2C+P+B">P. B. Stetson</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M+S">B. M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. M. Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Ibata%2C+R+A">R. A. Ibata</a>, <a href="/search/astro-ph?searchtype=author&query=Gibson%2C+B+K">B. K. Gibson</a>, <a href="/search/astro-ph?searchtype=author&query=Shara%2C+M">M. Shara</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0401440v1-abstract-short" style="display: inline;"> This paper presents new results from a photometric study of the main-sequence stars in M4, the closest globular cluster to the sun. Multi-field, multi-epoch observations at approximately 1, 2, and 6 core-radii were obtained with the WFPC2 camera on the HST. The multi-epoch observations allowed us to clean the data on the basis of proper motion. In all the fields the cluster main sequence can be… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0401440v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0401440v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0401440v1-abstract-full" style="display: none;"> This paper presents new results from a photometric study of the main-sequence stars in M4, the closest globular cluster to the sun. Multi-field, multi-epoch observations at approximately 1, 2, and 6 core-radii were obtained with the WFPC2 camera on the HST. The multi-epoch observations allowed us to clean the data on the basis of proper motion. In all the fields the cluster main sequence can be traced to at least V = 27.0 but there remains a trail of stars to the limit of the data near V = 30 in the deepest outer field. There is no evidence that we have reached the end of the hydrogen burning main sequence in any of our fields, however, there is some indication that very few stars remain to be detected in the deepest data. The scatter about the cluster main sequence yields a surprisingly small and variable binary fraction; f_b = 2% in the inner parts of the cluster falling to the 1% range outside. For the currently visible main sequence stars, the cluster mass function is very flat (alpha =0.1) in the outer field and flattens further in the inner fields suggesting well developed mass segregation. The observed variation in the mass function is broadly consistent with isotropic, multi-mass Michie-King models. Because we have a large sample of white dwarfs in the outer field we are able to show that the cluster IMF above 0.8Msun was considerably steeper than the present day mass function for low mass stars. Two appendicies are included in this contribution; a detailed discussion of the techniques used to reduce the data and a direct comparison between the cluster stars and those belonging to the inner spheroid of the Galaxy yielding a Galactocentric distance of 7.5+/-0.6 kpc. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0401440v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0401440v1-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 January, 2004; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2004. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">37 pages, 14 figures, submitted to AJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0309502">arXiv:astro-ph/0309502</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0309502">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0309502">ps</a>, <a href="https://arxiv.org/format/astro-ph/0309502">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1086/379800">10.1086/379800 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Pulsar-White Dwarf-Planet System in Messier 4: Improved Astrometry </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Ibata%2C+R">Rodrigo Ibata</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">Gregory G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Huber%2C+M">Mark Huber</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0309502v1-abstract-short" style="display: inline;"> A young and undermassive white dwarf has been identified as the possible companion to the millisecond pulsar PSR B1620-26 in Messier 4. This association is important as it then helps constrain the mass of the third body in the system to be of order a few times that of Jupiter. The presence of this planet in M4 has critical implications for planetary formation mechanisms in metal-poor environment… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0309502v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0309502v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0309502v1-abstract-full" style="display: none;"> A young and undermassive white dwarf has been identified as the possible companion to the millisecond pulsar PSR B1620-26 in Messier 4. This association is important as it then helps constrain the mass of the third body in the system to be of order a few times that of Jupiter. The presence of this planet in M4 has critical implications for planetary formation mechanisms in metal-poor environments such as globular clusters and the early Universe. The identification of the white dwarf is purely via the agreement in position between it and the pulsar and was limited by the accuracy of the pointing of HST which is +/-0.7 arcsec. We have redetermined the position of the white dwarf using ground-based data tied to USNOB-1.0 and find that the pulsar and white dwarf are now coincident to within 0.12 +/- 0.13 arcsec further strengthening the case for association between the two. We have also attempted to improve the proper motion measurement of the white dwarf by a maximum likelihood analysis of the stellar positions measured over a baseline of 5 years. While the errors are reduced by almost a factor of 6 from our previous work, we still have not resolved the cluster's intrinsic dispersion in proper motion. Thus the proper motion of the white dwarf with respect to the cluster itself is still not known although it is very small and is within 2-sigma of that of the cluster internal dispersion. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0309502v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0309502v1-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 September, 2003; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2003. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">9 pages, 2 figures, accepted for publication in the Astrophysical Journal (Letters)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophys.J.597:L45-L48,2003 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0307339">arXiv:astro-ph/0307339</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0307339">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1126/science.1086326">10.1126/science.1086326 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Young White Dwarf Companion to Pulsar 1620-26: Evidence for Early Planet Formation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Sigurdsson%2C+S">Steinn Sigurdsson</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M">Brad M. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Stairs%2C+I+H">Ingrid H. Stairs</a>, <a href="/search/astro-ph?searchtype=author&query=Thorsett%2C+S+E">Stephen E. Thorsett</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0307339v1-abstract-short" style="display: inline;"> The pulsar B1620-26 has two companions, one of stellar mass and one of planetary mass. We detected the stellar companion using Hubble Space Telescope observations. The color and magnitude of the stellar companion indicate that it is an undermassive white dwarf ($0.34 \pm 0.04 M_{\odot}$) of age $480\pm 140$ Myr. This places a constraint on the recent history of this triple system and supports a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0307339v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0307339v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0307339v1-abstract-full" style="display: none;"> The pulsar B1620-26 has two companions, one of stellar mass and one of planetary mass. We detected the stellar companion using Hubble Space Telescope observations. The color and magnitude of the stellar companion indicate that it is an undermassive white dwarf ($0.34 \pm 0.04 M_{\odot}$) of age $480\pm 140$ Myr. This places a constraint on the recent history of this triple system and supports a scenario in which the current configuration arose through a dynamical exchange interaction in the cluster core. This implies that planets may be relatively common in low-metallicity globular clusters and that planet formation is more widespread and happened earlier than previously believed. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0307339v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0307339v1-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 July, 2003; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2003. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">4 pages, published in Science</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Science 301:193-196,2003 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0306241">arXiv:astro-ph/0306241</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0306241">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0306241">ps</a>, <a href="https://arxiv.org/format/astro-ph/0306241">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1086/377320">10.1086/377320 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The CFHT Open Star Cluster Survey. IV. Two Rich, Young Open Star Clusters: NGC 2168 (M35) and NGC 2323 (M50) </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jasonjot S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">Gregory G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Ventura%2C+P">Paolo Ventura</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0306241v2-abstract-short" style="display: inline;"> We continue our study of rich Galactic clusters by presenting deep CCD observations of both NGC 2168 (M35) and NGC 2323 (M50). Both clusters are found to be rich (NGC 2168 contains at least 1000 stars brighter than V = 22 and NGC 2323 contains approximately 2100 stars brighter than our photometric limit of V = 23) and young (age of NGC 2168 = 180 Myrs, age of NGC 2323 = 130 Myrs). The color-magn… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0306241v2-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0306241v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0306241v2-abstract-full" style="display: none;"> We continue our study of rich Galactic clusters by presenting deep CCD observations of both NGC 2168 (M35) and NGC 2323 (M50). Both clusters are found to be rich (NGC 2168 contains at least 1000 stars brighter than V = 22 and NGC 2323 contains approximately 2100 stars brighter than our photometric limit of V = 23) and young (age of NGC 2168 = 180 Myrs, age of NGC 2323 = 130 Myrs). The color-magnitude diagrams for the clusters exhibit clear main sequences stretching over 14 magnitudes in the V, B-V plane. Comparing these long main sequences with those of earlier clusters in the survey, as well as with the Hyades, has allowed for accurate distances to be established for each cluster (dist. of NGC 2168 = 912 +/- 70/65 pc, dist. of NGC 2323 = 1000 +/- 81/75 pc). Analysis of the luminosity and mass functions suggest that despite their young ages, both clusters are somewhat dynamically relaxed exhibiting signs of mass-segregation. This is especially interesting in the case of NGC 2323, which has an age of only 1.3 times the dynamical relaxation time. The present photometry is also deep enough to detect all of the white dwarfs in both clusters. We discuss some interesting candidates which may be the remnants of quite massive (M > 5 Mo) progenitor stars. The white dwarf cooling age of NGC 2168 is found to be in good agreement with the main-sequence turn-off age. These objects are potentially very important for setting constraints on the white dwarf initial-final mass relationship and upper mass limit for white dwarf production. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0306241v2-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0306241v2-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, 2003; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 11 June, 2003; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2003. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">34 pages, including 12 diagrams and 5 tables. Accepted for publication in AJ. Minor typos corrected</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astron.J. 126 (2003) 1402 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0304470">arXiv:astro-ph/0304470</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0304470">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0304470">ps</a>, <a href="https://arxiv.org/format/astro-ph/0304470">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1086/380219">10.1086/380219 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Searching for Variability in the Globular Cluster Messier 4 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Ferdman%2C+R+D">Robert D. Ferdman</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Brewer%2C+J">James Brewer</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">Greg G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Gibson%2C+B+K">Brad K. Gibson</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M+S">Brad M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Huber%2C+M+E">Mark E. Huber</a>, <a href="/search/astro-ph?searchtype=author&query=Ibata%2C+R+A">Rodrigo A. Ibata</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jasonjot S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Matthews%2C+J+M">Jaymie M. Matthews</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Rowe%2C+J+F">Jason F. Rowe</a>, <a href="/search/astro-ph?searchtype=author&query=Shara%2C+M+M">Michael M. Shara</a>, <a href="/search/astro-ph?searchtype=author&query=Stetson%2C+P+B">Peter B. Stetson</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0304470v2-abstract-short" style="display: inline;"> Time-series data taken with the Hubble Space Telescope of a field six core radii (~5') from the center of the globular cluster Messier 4, and covering a period of about 10 weeks in early 2001, have been analyzed in search of variable objects. Various criteria were employed to select candidate variable stars. Period searches were performed on the selected candidates using phase dispersion minimiz… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0304470v2-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0304470v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0304470v2-abstract-full" style="display: none;"> Time-series data taken with the Hubble Space Telescope of a field six core radii (~5') from the center of the globular cluster Messier 4, and covering a period of about 10 weeks in early 2001, have been analyzed in search of variable objects. Various criteria were employed to select candidate variable stars. Period searches were performed on the selected candidates using phase dispersion minimization (PDM). The reliability of the PDM search results was tested using synthetic light curves of eclipsing binary stars and sinusoidal light curves of different periods. Results from this analysis showed that there are probably no eclipsing binary stars or periodic variables in our field with periods on the order of a few hours to a few days, down to limiting magnitudes of V~25 and I~24, which is consistent with the absence of contact binaries such as W Ursae Majoris systems. However, one candidate variable star does show an increase in brightness of ~0.1 magnitudes in both bandpasses, which seems to last for a few days. Possible explanations concerning the nature of this object include a binary system with a white dwarf primary and a low-mass main sequence secondary, or a BY Draconis variable star. We are able to set an upper limit to the observed fraction of photometric variability in this dataset of 0.05%. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0304470v2-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0304470v2-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, 2003; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 April, 2003; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2003. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">36 pages including 12 figures, accepted to the Astronomical Journal. References added; typos fixed; paper made more concise at referee's recommendation</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0304036">arXiv:astro-ph/0304036</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0304036">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0304036">ps</a>, <a href="https://arxiv.org/format/astro-ph/0304036">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1086/380432">10.1086/380432 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Galactic Inner Halo: Searching for White Dwarfs and Measuring the Fundamental Galactic Constant, Vo/Ro </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jasonjot S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M">Brad M. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Stetson%2C+P+B">Peter B. Stetson</a>, <a href="/search/astro-ph?searchtype=author&query=Shara%2C+M+M">Michael M. Shara</a>, <a href="/search/astro-ph?searchtype=author&query=Saviane%2C+I">Ivo Saviane</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Limongi%2C+M">Marco Limongi</a>, <a href="/search/astro-ph?searchtype=author&query=Ibata%2C+R">Rodrigo Ibata</a>, <a href="/search/astro-ph?searchtype=author&query=Gibson%2C+B+K">Brad K. Gibson</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">Gregory G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Brewer%2C+J">James Brewer</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0304036v2-abstract-short" style="display: inline;"> We establish an extragalactic, zero-motion frame of reference within the deepest optical image of a globular star cluster, an HST 123-orbit exposure of M4 (GO 8679, cycle 9). The line of sight beyond M4 (l,b (deg) = 351,16) intersects the inner halo (spheroid) of our Galaxy at a tangent-point distance of 7.6 kpc (for Ro = 8 kpc). We isolate these spheroid stars from the cluster based on their pr… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0304036v2-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0304036v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0304036v2-abstract-full" style="display: none;"> We establish an extragalactic, zero-motion frame of reference within the deepest optical image of a globular star cluster, an HST 123-orbit exposure of M4 (GO 8679, cycle 9). The line of sight beyond M4 (l,b (deg) = 351,16) intersects the inner halo (spheroid) of our Galaxy at a tangent-point distance of 7.6 kpc (for Ro = 8 kpc). We isolate these spheroid stars from the cluster based on their proper motions over the 6-year baseline between these and previous epoch HST data (GO 5461, cycle 4). Distant background galaxies are also found on the same sight line using image-morphology techniques. This fixed reference frame allows us to independently determine the fundamental Galactic constant, Vo/Ro = 25.3 +/- 2.6 km/s/kpc, thus providing a velocity of the Local Standard of Rest, v = 202.7 +/- 24.7 km/s for Ro = 8.0 +/- 0.5 kpc. Secondly, the galaxies allow a direct measurement of M4's absolute proper motion, mu_total = 22.57 +/- 0.76 mas/yr, in excellent agreement with recent studies. The clear separation of galaxies from stars in these deep data also allow us to search for inner-halo white dwarfs. We model the conventional Galactic contributions of white dwarfs along our line of sight and predict 7.9 (thin disk), 6.3 (thick disk) and 2.2 (spheroid) objects to the limiting magnitude at which we can clearly delineate stars from galaxies (V = 29). An additional 2.5 objects are expected from a 20% white dwarf dark halo consisting of 0.5 Mo objects, 70% of which are of the DA type. After considering the kinematics and morphology of the objects in our data set, we find the number of white dwarfs to be consistent with the predictions for each of the conventional populations. However, we do not find any evidence for dark halo white dwarfs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0304036v2-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0304036v2-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, 2003; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 1 April, 2003; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2003. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">31 pages, including 6 diagrams and 2 tables. Accepted for publication in ApJ</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophys.J. 601 (2004) 277-288 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0206186">arXiv:astro-ph/0206186</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0206186">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0206186">ps</a>, <a href="https://arxiv.org/format/astro-ph/0206186">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361:20020858">10.1051/0004-6361:20020858 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The white dwarf cooling sequence in the old open cluster NGC 188 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Andreuzzi%2C+G">Gloria Andreuzzi</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Limongi%2C+M">Marco Limongi</a>, <a href="/search/astro-ph?searchtype=author&query=Bolte%2C+M">Michael Bolte</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0206186v1-abstract-short" style="display: inline;"> We develop the white dwarf luminosity function (LF) of the old open cluster NGC 188 in order to determine a lower limit to the age of the cluster by using the faint end of the cooling sequence. To produce an extensive sequence of the cooling white dwarfs we imaged four contiguous HST-WFPC2 fields in the center of the cluster in the F555W and F814W filters. After imposing selection criteria on… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0206186v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0206186v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0206186v1-abstract-full" style="display: none;"> We develop the white dwarf luminosity function (LF) of the old open cluster NGC 188 in order to determine a lower limit to the age of the cluster by using the faint end of the cooling sequence. To produce an extensive sequence of the cooling white dwarfs we imaged four contiguous HST-WFPC2 fields in the center of the cluster in the F555W and F814W filters. After imposing selection criteria on the detected objects we found a white dwarf cooling sequence (down to V ~26.5) including 28 candidate white dwarfs in the cluster. The exposures are not deep enough to reach the end of this sequence, but the results of our analysis allow us to establish a lower limit to the age of the cluster independently of the isochrone fit to the cluster turnoff. The most ancient white dwarfs found are ~4 Gyr old, an age that is set solely by the photometric limit of our data. Classical methods provide an estimate of \~7 Gyr (Sarajedini et al., 1999). <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0206186v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0206186v1-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, 2002; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2002. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">6 pages, 5 figures, accepted on Astronomy and Astrophysics</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0205087">arXiv:astro-ph/0205087</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0205087">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0205087">ps</a>, <a href="https://arxiv.org/format/astro-ph/0205087">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1086/342528">10.1086/342528 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The White Dwarf Cooling Sequence of the Globular Cluster Messier 4 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M+S">Brad M. S. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Brewer%2C+J">James Brewer</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">Greg G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Gibson%2C+B+K">Brad K. Gibson</a>, <a href="/search/astro-ph?searchtype=author&query=Ibata%2C+R">Rodrigo Ibata</a>, <a href="/search/astro-ph?searchtype=author&query=Limongi%2C+M">Marco Limongi</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Shara%2C+M+M">Michael M. Shara</a>, <a href="/search/astro-ph?searchtype=author&query=Stetson%2C+P+B">Peter B. Stetson</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0205087v1-abstract-short" style="display: inline;"> We present the white dwarf sequence of the globular cluster M4, based on a 123 orbit Hubble Space Telescope exposure, with limiting magnitude V = 30, I = 28. The white dwarf luminosity function rises sharply for I >25.5, consistent with the behaviour expected for a burst population. The white dwarfs of M4 extend to approximately 2.5 magnitudes fainter than the peak of the local Galactic disk whi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0205087v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0205087v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0205087v1-abstract-full" style="display: none;"> We present the white dwarf sequence of the globular cluster M4, based on a 123 orbit Hubble Space Telescope exposure, with limiting magnitude V = 30, I = 28. The white dwarf luminosity function rises sharply for I >25.5, consistent with the behaviour expected for a burst population. The white dwarfs of M4 extend to approximately 2.5 magnitudes fainter than the peak of the local Galactic disk white dwarf luminosity function. This demonstrates a clear and significant age difference between the Galactic disk and the halo globular cluster M4. Using the same standard white dwarf models (Hansen 1999) to fit each luminosity function yields ages of 7.3 +/- 1.5 Gyr for the disk and 12.7 +/- 0.7 Gyr for M4 (2-sigma statistical errors). <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0205087v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0205087v1-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 May, 2002; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2002. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">14 pages, 4 diagrams. Accepted for publication in the Astrophysical Journal Letters</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophys.J.574:L155-L158,2002 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0205086">arXiv:astro-ph/0205086</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0205086">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0205086">ps</a>, <a href="https://arxiv.org/format/astro-ph/0205086">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1086/342527">10.1086/342527 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Lower Main Sequence and Mass Function of the Globular Cluster Messier 4 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Brewer%2C+J">James Brewer</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">Gregory G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Gibson%2C+B+K">Brad K. Gibson</a>, <a href="/search/astro-ph?searchtype=author&query=Hansen%2C+B+M">Brad M. Hansen</a>, <a href="/search/astro-ph?searchtype=author&query=Ibata%2C+R">Rodrigo Ibata</a>, <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jasonjot S. Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Limongi%2C+M">Marco Limongi</a>, <a href="/search/astro-ph?searchtype=author&query=Rich%2C+R+M">R. Michael Rich</a>, <a href="/search/astro-ph?searchtype=author&query=Saviane%2C+I">Ivo Saviane</a>, <a href="/search/astro-ph?searchtype=author&query=Shara%2C+M+M">Michael M. Shara</a>, <a href="/search/astro-ph?searchtype=author&query=Stetson%2C+P+B">Peter B. Stetson</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0205086v2-abstract-short" style="display: inline;"> The deepest optical image ever in a globular star cluster, a Hubble Space Telescope (HST) 123 orbit exposure in a single field of Messier 4, was obtained in 2 filters (F606W, F814W) over a 10 week period in early 2001. A somewhat shallower image obtained in 1995 allowed us to select out cluster and field objects via their proper motion displacement resulting in remarkably clean color-magnitude d… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0205086v2-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0205086v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0205086v2-abstract-full" style="display: none;"> The deepest optical image ever in a globular star cluster, a Hubble Space Telescope (HST) 123 orbit exposure in a single field of Messier 4, was obtained in 2 filters (F606W, F814W) over a 10 week period in early 2001. A somewhat shallower image obtained in 1995 allowed us to select out cluster and field objects via their proper motion displacement resulting in remarkably clean color-magnitude diagrams that reach to V = 30, I = 28. The cluster main sequence luminosity function contains very few stars fainter than MV = 15.0, MI = 11.8 which, in both filters, is more than 2 magnitudes brighter than our limit. This is about the faintest luminosity seen among field Population II subdwarfs of the same metallicity. However, there remains a sprinkling of potential cluster stars to lower luminosity all the way down to our limiting magnitudes. These latter objects are significantly redder than any known metal-poor field subdwarf. Comparison with the current generation of theoretical stellar models implies that the masses of the lowest luminosity cluster stars observed are near 0.09 Msun. We derive the mass function of the cluster in our field and find that it is very slowly rising towards the lowest masses with no convincing evidence of a turnover even below 0.1 Msun. The formal slope between 0.65 and 0.09 Msun is alpha = 0.75 (Salpeter of 2.35) with a 99% confidence interval 0.55 - 1.05. A consistency check between these slopes and the number of observed cluster white dwarfs yields a range of possible conclusions, one of which is that we have indeed seen the termination of the white dwarf cooling sequence in M4. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0205086v2-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0205086v2-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, 2002; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 6 May, 2002; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2002. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">12 pages, 3 diagrams. To be published in the Astrophysical Journal Letters August 2002. Several minor edits and a different figure 2 from original submission</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophys.J. 574 (2002) L151-L154 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0109368">arXiv:astro-ph/0109368</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0109368">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0109368">ps</a>, <a href="https://arxiv.org/format/astro-ph/0109368">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1086/324463">10.1086/324463 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The CFHT Open Star Cluster Survey. III. The White Dwarf Cooling Age of the Rich Open Star Cluster NGC 2099 (M37) </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kalirai%2C+J+S">Jasonjot Singh Kalirai</a>, <a href="/search/astro-ph?searchtype=author&query=Ventura%2C+P">Paolo Ventura</a>, <a href="/search/astro-ph?searchtype=author&query=Richer%2C+H+B">Harvey B. Richer</a>, <a href="/search/astro-ph?searchtype=author&query=Fahlman%2C+G+G">Gregory G. Fahlman</a>, <a href="/search/astro-ph?searchtype=author&query=Durrell%2C+P+R">Patrick R. Durrell</a>, <a href="/search/astro-ph?searchtype=author&query=D%27Antona%2C+F">Francesca D'Antona</a>, <a href="/search/astro-ph?searchtype=author&query=Marconi%2C+G">Gianni Marconi</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0109368v1-abstract-short" style="display: inline;"> We present deep CCD photometry of the very rich, intermediate aged (similar to the Hyades) open star cluster NGC 2099 (M37). The V, B-V color-magnitude diagram (CMD) for the cluster shows an extremely well populated and very tightly constrained main-sequence extending over 12 magnitudes from the turn-off. The CFH12K photometry for this cluster is faint enough (V ~ 24.5) to detect the remnants of… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0109368v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0109368v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0109368v1-abstract-full" style="display: none;"> We present deep CCD photometry of the very rich, intermediate aged (similar to the Hyades) open star cluster NGC 2099 (M37). The V, B-V color-magnitude diagram (CMD) for the cluster shows an extremely well populated and very tightly constrained main-sequence extending over 12 magnitudes from the turn-off. The CFH12K photometry for this cluster is faint enough (V ~ 24.5) to detect the remnants of the most massive progenitor cluster stars under the Type I SNe limit. Therefore, the CMD of the cluster also exhibits a well defined white dwarf `clump' caused by the decreased rate of cooling of these stars as they age, and a subsequent gap with very few objects. The termination point (Mv = 11.95 +/- 0.30) of the white dwarf luminosity function gives a white dwarf cooling age of 566 +/- 154/176 Myrs which is in excellent agreement with the main-sequence turn-off isochrone age (520 Myrs). By carefully accounting for errors, we show that the cooling age confirms that models including convective core overshooting are preferred for young-intermediate aged clusters. We also derive the reddening (E(B-V) = 0.21 +/- 0.03) and distance ((m-M)v = 11.55 +/- 0.13) to NGC 2099 by matching main-sequence features in the cluster to a new fiducial main-sequence for the Hyades. As a continuing part of the goals of the CFHT Open Star Cluster Survey to better understand dynamical processes of open clusters, we also fit a King model to the cluster density distribution and investigate the cluster main-sequence luminosity and mass functions in increasing concentric annuli. We find some evidence for mass segregation within the boundary of NGC 2099 as expected given the cluster's age relative to the dynamical age. The present global mass function for the cluster is found to be shallower than a Salpeter IMF. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0109368v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0109368v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 20 September, 2001; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2001. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">15 Figures and 6 Tables -- 48 pages. Accepted for publication in AJ. Higher resolution images available at http://www.astro.ubc.ca/~jkalirai/research.html</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astron.J. 122 (2001) 3239 </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=Richer%2C+H+B&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Richer%2C+H+B&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Richer%2C+H+B&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 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