Observations of white dwarfs in the solar neighborhood

Abstract

High proper motion surveys are still adding much to our understanding of the local white dwarf population and, possibly, to the Galactic halo membership of some objects. As part of our study of white dwarfs in the solar neighborhood we have observed seven white dwarfs from the revised New Luyten Two Tenths (NLTT) catalog of Salim & Gould. We found four DA white dwarfs (NLTT 529, 49985, 53468, 55932), one DZ white dwarf (NLTT 40607) that shows a close resemblance to the unusual DZ white dwarf G165-7, and two DC white dwarfs (NLTT 19138, NLTT 52404). The white dwarf candidates were chosen using the V-J reduced proper-motion diagram of Salim & Gould and an optical-infrared diagram (V-Jvs. J-H). We also observed five stars from the list of local white dwarfs by Holberg, Oswalt, & Sion that required confirmation of their spectral classification. We confirm that GD 1212 and WD 1717-345 are white dwarfs but that BPM 17113 (WD 0311-543), KUV 05097+1649, and BPM 19929 (WD 1013-559) are main-sequence F stars rather than white dwarfs. An analysis of a color-selected sample of white dwarf candidates extracted from the rNLTT catalog could contribute more than 200 new white dwarfs, most belonging to the thin disk, with a few (N<15) kinematically selected members of an older population (thick disk or halo).