Calculating White Dwarf Stellar Parameters from Survey Data

The effective temperatures and masses of white dwarfs have historically been estimated by fitting spectral lines to theoretical model atmospheres. This method has had problems however, because the resulting parameters depend on which spectral line is used to perform the fit. This suggests there are other factors influencing the spectral lines, which is introducing uncertainty to the temperature and mass calculations. To improve upon the traditional method of calculating stellar parameters, we have estimated them without using spectral line fits. Instead, we combined parallaxes measured in the Gaia survey, with atmospheric model fits to fluxes from the Sloan Digital Sky Survey (SDSS) to find the best fit temperature and radius of each star in a sample of 87 DA (hydrogen atmosphere) white dwarfs.

These new temperatures and gravities do not suffer from the same systematic errors as line fits, and may improve the white dwarf ages used in cosmochronology, provide more precise masses for the initial-final mass relation, and calibrate the temperature scale for the DA white dwarfs. This research may also shed light on the other factors influencing the spectral line fits, and provide insight into the physics of how metal lines form.