Refining our knowledge of the white dwarf mass-radius relation

TL;DR

This paper improves measurements of Sirius B's mass and radius using advanced spectroscopic techniques, enabling more precise tests of white dwarf theoretical models and extending the methodology to other binary systems.

Contribution

It refines observational methods for white dwarf mass-radius measurements, reducing systematic errors and applying the approach to a broader sample for better theoretical testing.

Findings

Enhanced spectroscopic data of Sirius B with reduced systematic errors

Preliminary refined measurements of Sirius B's mass and radius

Extension of measurement techniques to other white dwarf binaries

Abstract

The presence of a white dwarf in a resolved binary system, such as Sirius, provides an opportunity to combine dynamical information about the masses, from astrometry and spectroscopy, with a gravitational red-shift measurement and spectrophotometry of the white dwarf atmosphere to provide a test of theoretical mass-radius relations of unprecedented accuracy. We demonstrated this with the first Balmer line spectrum of Sirius B to be obtained free of contamination from the primary, with STIS on HST. However, we also found an unexplained discrepancy between the spectroscopic and gravitational red-shift mass determinations. With the recovery of STIS, we have been able to revisit our observations of Sirius B with an improved observation strategy designed to reduce systematic errors on the gravitational red-shift measurement. We provide a preliminary report on the refined precision of the Sirius B mass-radius measurements and the extension of this technique to a larger sample of white dwarfs in resolved binaries. Together these data can provide accurate mass and radius determinations capable of testing the theoretical mass-radius relation and distinguishing between possible structural models.