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arXiv · 0804.1570

A Nearby Old Halo White Dwarf Candidate from the Sloan Digital Sky Survey

Patrick B. Hall·Piotr M. Kowalski·Hugh C. Harris·Akshay Awal·S. K. Leggett·Mukremin Kilic·Scott F. Anderson·Evalyn Gates
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Abstract

We report the discovery of a nearby, old, halo white dwarf candidate from the Sloan Digital Sky Survey. SDSS J110217.48+411315.4 has a proper motion of 1.75 arcsec/year and redder optical colors than all other known featureless (type DC) white dwarfs. We present SDSS imaging and spectroscopy of this object, along with near-infrared photometry obtained at the United Kingdom Infra-Red Telescope. Fitting its photometry with up-to-date model atmospheres, we find that its overall spectral energy distribution is fit reasonably well with a pure hydrogen composition and T_eff~3800 K (assuming log g=8). That temperature and gravity would place this white dwarf at 35 pc from the Sun with a tangential velocity of 290 km/s and space velocities consistent with halo membership; furthermore, its combined main sequence and white dwarf cooling age would be ~11 Gyr. However, if this object is a massive white dwarf, it could be a younger object with a thick disk origin. Whatever its origin, the optical colors of this object are redder than predicted by any current pure hydrogen, pure helium or mixed hydrogen-helium atmospheric model, indicating that there remain problems in our understanding of the complicated physics of the dense atmospheres of cool white dwarfs.

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Patrick B. Hall, Piotr M. Kowalski, Hugh C. Harris, Akshay Awal, S. K. Leggett, Mukremin Kilic, Scott F. Anderson, Evalyn Gates. 2008-04-09. A Nearby Old Halo White Dwarf Candidate from the Sloan Digital Sky Survey. https://doi.org/10.1088/0004-6256%2F136%2F1%2F76

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