Discovery of 282 Cool White Dwarfs (Teff⪉8000 K) in the Sloan Digital Sky Survey

Publication Title

14th European Workshop on White Dwarfs, ASP Conference Series

Document Type



We report the discovery of 282 white dwarfs with Teff⪉ 8000 K in the Sloan Digital Sky Survey (SDSS) Data Release 2 imaging area. A reduced proper motion diagram utilizing accurate SDSS magnitudes and USNO plate astrometry is used to separate cool white dwarf candidates from metal-weak, high-velocity main sequence Population II stars (subdwarfs). Using spectra from the HET, the MMT, and the McDonald 2.7m Telescope plus additional SDSS spectroscopy, we determined the white dwarf fraction at various locations in the reduced proper motion diagram, and demonstrated that the contamination level by subdwarfs is small near the cool white dwarf locus. The high white dwarf counts near this locus has important implications for white dwarf luminosity function studies. Photometry and the reduced proper motion diagram (without follow-up spectroscopy) allow nearly complete identification of white dwarfs for u-g≤ 1.0 (Teff≥ 5500 K). The majority of objects in our sample show disk kinematics, though several objects with Teff≥ 5000 K display halo kinematics. Nevertheless, these objects are probably too warm/young to be halo objects.


Physics and Astronomy





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