NOAO >   Observing Info >   Approved Programs >   2015A-0292

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Program Information for 2015A-0292


PI: Saurav Dhital, Embry-Riddle Aeronautical U., dhitals@erau.edu
Address: Physical Sciences, 600 S. Clyde Morris Blvd, Daytona Beach, FL 32114 USA

CoI: Terry D Oswalt, Embry-Riddle Aeronautical U.
CoI: Jay Holberg, U. of Arizona

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 $\lesssim$5\% 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.

Program Type: Standard/Galactic

Scheduled Nights:
Run 1 (2015A):  SOAR/Goodman -- 4n on Apr 10 - Apr 11 2015, Apr 13 - Apr 14 2015
Run 2 (2015A):  KP-4m/RCSP -- 5n on Feb 23 - Feb 25 2015, Jun 24 - Jun 25 2015


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