A SPECTROSCOPIC ANALYSIS OF WHITE DWARFS IN THE KISO SURVEY

Abstract

We present a spectroscopic analysis of white dwarfs found in the Kiso survey. Spectroscopic observations at high signal-to-noise ratio have been obtained for all DA and DB stars in the Kiso Schmidt ultraviolet excess survey (KUV stars). These observations led to the reclassification of several KUV objects, including the discovery of three unresolved DA+DB double degenerate binaries. The atmospheric parameters (Teff and log g) are obtained from detailed model atmosphere fits to optical spectroscopic data. The mass distribution of our sample is characterized by a mean value of 0.606 Msun and a dispersion of 0.135 Msun for DA stars, and 0.758 Msun and a dispersion of 0.192 Msun for DB stars. Absolute visual magnitudes obtained from our spectroscopic fits allow us to derive an improved luminosity function for the DA and DB stars identified in the Kiso survey. Our luminosity function is found to be significantly different from earlier estimates based on empirical photometric calibrations of Mv for the same sample. The results for the DA stars now appear entirely consistent with those obtained for the PG survey using the same spectroscopic approach. The space density for DA stars with Mv<12.75 is 2.80X10^-4 pc^-3 in the Kiso survey, which is 9.6% smaller than the value found in the PG survey. The completeness of both surveys is briefly discussed.