Patrick B. Hall et al. 2008 The Astronomical Journal 136 76 doi:10.1088/0004-6256/136/1/76
A NEARBY OLD HALO WHITE DWARF CANDIDATE FROM THE SLOAN DIGITAL SKY SURVEY
FREE ISSUEPatrick B. Hall1, Piotr M. Kowalski2, Hugh C. Harris3, Akshay Awal1,4, S. K. Leggett5, Mukremin Kilic6, Scott F. Anderson7 and Evalyn Gates8
Show affiliationsWe report the discovery of a nearby old halo white dwarf (WD) candidate from the Sloan Digital Sky Survey (SDSS). SDSS J110217.48+411315.4 has a proper motion of 1
75 yr–1 and redder optical colors than all other known featureless (type DC) WDs. We present SDSS imaging and spectroscopy of this object, along with near-infrared photometry obtained at the United Kingdom Infrared Telescope (UKIRT). 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). This temperature and gravity would place this WD at 35 pc from the Sun with a tangential velocity of 290 km s–1 and space velocities consistent with halo membership; furthermore, its combined main-sequence and WD cooling age would be 11 Gyr. However, if this object is a massive WD, 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 WDs.
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Issue 1 (2008 July)
Received 2008 February 22, accepted for publication 2008 April 3
Published 2008 May 27
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A Nearby Old Halo White Dwarf Candidate from the Sloan Digital Sky Survey
Patrick B. Hall et al. 2008 The Astronomical Journal 136 76
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