Barstow, M. A. Bond, H. E. Burleigh, M. R. Casewell, S. L. Farihi, J. Holberg, J. B. Hubeny, I. Refining our knowledge of the white dwarf mass-radius relation with HST observations of Sirius-type binaries 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. Solar and Stellar Astrophysics (astro-ph.SR) 2017-02-24
    https://figshare.le.ac.uk/articles/journal_contribution/Refining_our_knowledge_of_the_white_dwarf_mass-radius_relation_with_HST_observations_of_Sirius-type_binaries/10159691