The Gaia DR1 Mass-Radius Relation for White Dwarfs

TL;DR

This paper uses Gaia DR1 data combined with spectroscopic parameters to examine the white dwarf mass-radius relation, finding good agreement with theoretical models but limited by current measurement uncertainties.

Contribution

It provides the first Gaia DR1-based analysis of white dwarf mass-radius relation, highlighting the data's current limitations and future potential with Gaia DR2.

Findings

Good agreement between Gaia parallaxes and theoretical MRRs

Uncertainties dominated by spectroscopic atmospheric parameters

Current data cannot characterize hydrogen envelope masses

Abstract

The Gaia Data Release 1 (DR1) sample of white dwarf parallaxes is presented, including 6 directly observed degenerates and 46 white dwarfs in wide binaries. This data set is combined with spectroscopic atmospheric parameters to study the white dwarf mass-radius relationship (MRR). Gaia parallaxes and G magnitudes are used to derive model atmosphere dependent white dwarf radii, which can then be compared to the predictions of a theoretical MRR. We find a good agreement between Gaia DR1 parallaxes, published effective temperatures (Teff) and surface gravities (log g), and theoretical MRRs. As it was the case for Hipparcos, the precision of the data does not allow for the characterisation of hydrogen envelope masses. The uncertainties on the spectroscopic atmospheric parameters are found to dominate the error budget and current error estimates for well-known and bright white dwarfs may be slightly optimistic. With the much larger Gaia DR2 white dwarf sample it will be possible to explore the MRR over a much wider range of mass, Teff, and spectral types.