Accession Number : ADA494546


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


Descriptive Note : Journal article


Corporate Author : NAVAL OBSERVATORY WASHINGTON DC


Personal Author(s) : Hall, Patrick B ; Kowalski, Piotr M ; Harris, Hugh C ; Awal, Akshay ; Leggett, S K ; Kilic, Mukremin ; Anderson, Scott F ; Gates, Evalyn


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a494546.pdf


Report Date : Jul 2008


Pagination or Media Count : 8


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 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 Teff H 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 H11 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.


Descriptors :   *DWARF STARS , REPRINTS , OPTICAL PROPERTIES , SPECTROSCOPY , HYDROGEN , SURVEYS , IMAGES , SPECTRAL ENERGY DISTRIBUTION , NEAR INFRARED RADIATION , INFRARED TELESCOPES , PHOTOMETRY , VELOCITY , COLORS


Subject Categories : Astronomy


Distribution Statement : APPROVED FOR PUBLIC RELEASE