PI: Saurav Dhital, Embry-Riddle Aeronautical University, firstname.lastname@example.org
Address: Physical Sciences, 600 S. Clyde Morris Blvd, Daytona Beach, FL 32114, USA
CoI: Terry D. Oswalt, Embry-Riddle Aeronautical University
CoI: J. B. Holberg, University of Arizona
CoI: Jingkun Zhao, National Astronomical Observatories, China
Title: Observational Constraints on the White Dwarf Mass–Radius Relation
Abstract: We propose to measure gravitational redshifts for white dwarf stars that have distant, non-interacting main-sequence companions. With independent radius constraints obtained from parallaxes and surface gravity determinations obtained by fitting the Balmer series from our spectra, we will make improved estimates of white dwarf masses and radii that can be critically compared with theoretical mass-radius relations specific to each star. These observations will allow us to examine serious discrepancies between the theoretical and empirical measurements of the white dwarf mass-radius relation and extend the range of masses over which it has been tested, spanning 0.5-1.2 \Msun. Currently, the measured radius for only a single WD matches its predicted value within 5%. With the expected precision of \lesssim5% for over half the sample, we will also distinguish whether the white dwarfs have ``thick'' or ``thin'' H envelopes. Using the same spectra, we will also estimate the metallicity of the main-sequence companion and examine how the initial-final-mass ratio for WDs depends on metallicity. Thus, this project will put robust constraints on two fundamental relations that govern our understanding of white dwarfs: the mass-ratio and the initial-final-mass relations.
National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360