SIMBAD references

We determined masses for the 7167 DA and 507 DB white dwarf stars classified as single and non-magnetic in Data Release 4 of the Sloan Digital Sky Survey (SDSS). We obtained revised T_effand logg determinations for the most massive stars by fitting the SDSS optical spectra with a synthetic spectra grid derived from model atmospheres extending to logg = 10.0. We also calculate radii from evolutionary models and create volume-corrected mass distributions for our DA and DB samples. The mean mass for the DA stars brighter than g = 19 and hotter than T_eff= 12000K is. For the 150 DBs brighter than g = 19 and hotter than T_eff= 16000K, we find. It appears the mean mass for DB white dwarf stars may be significantly larger than that for DAs. We also report the highest mass white dwarf stars ever found, up to.