White-Dwarfs in the thin-disk: physical properties and luminosity functions

Abstract

In this article, we present an investigation of a sample of 1072 stars extracted from the Villanova Catalog of Spectroscopically Identified White Dwarfs (2005 on-line version), studying their distribution in the Galaxy, their physical properties and their luminosity functions. The distances and physical properties of the white dwarfs are determined through interpolation of their (B-V) or (b-y) colors in model grids. The solar position relative to the Galactic plane, luminosity function, as well as separate functions for each white dwarf spectral type are derived and discussed. We show that the binary fraction does not vary significantly as a function of distance from the Galactic disk out to 100 pc. We propose that the formation rates of DA and non-DAs have changed over time and/or that DAs evolve into non-DA types. The luminosity functions for DAs and DBs have peaks possibly related to a star burst event.