a Nearby Old Halo White Dwarf Candidate from the Sloan Digital Sky Survey
Abstract
We 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 1farcs75 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.
- Publication:
-
The Astronomical Journal
- Pub Date:
- July 2008
- DOI:
- 10.1088/0004-6256/136/1/76
- arXiv:
- arXiv:0804.1570
- Bibcode:
- 2008AJ....136...76H
- Keywords:
-
- stars: individual: SDSS J110217.48+411315.4;
- white dwarfs;
- Astrophysics
- E-Print:
- AJ in press. 10 pages emulateapj format