The McDonald Accelerating Stars Survey (MASS): White Dwarf Companions Accelerating the Sun-like Stars 12 Psc and HD 159062

TL;DR

This study reports the discovery and precise dynamical mass measurements of white dwarf companions to two Sun-like stars, using long-term radial velocity, astrometry, and adaptive optics imaging, providing benchmarks for white dwarf models.

Contribution

It presents the first dynamical mass measurements of white dwarf companions to 12 Psc and HD 159062, combining multiple observational techniques for accurate characterization.

Findings

Masses of white dwarf companions are approximately 0.605 and 0.609 solar masses.

Orbits have semi-major axes of about 40 and 60 AU, with high eccentricity and low eccentricity, respectively.

Results serve as benchmarks for white dwarf mass-radius models and AGB wind accretion studies.

Abstract

We present the discovery of a white dwarf companion to the G1 V star 12 Psc found as part of a Keck adaptive optics imaging survey of long-term accelerating stars from the McDonald Observatory Planet Search Program. Twenty years of precise radial-velocity monitoring of 12 Psc with the Tull Spectrograph at the Harlan J. Smith telescope reveals a moderate radial acceleration ($\approx$10 m s$^{-1}$ yr $^{-1}$), which together with relative astrometry from Keck/NIRC2 and the astrometric acceleration between $Hipparcos$ and $Gaia$ DR2 yields a dynamical mass of $M_B$ = 0.605$^{+0.021}_{-0.022}$ $M_{\odot}$ for 12 Psc B, a semi-major axis of 40$^{+2}_{-4}$ AU, and an eccentricity of 0.84$\pm$0.08. We also report an updated orbit fit of the white dwarf companion to the metal-poor (but barium-rich) G9 V dwarf HD 159062 based on new radial velocity observations from the High-Resolution Spectrograph at the Hobby-Eberly Telescope and astrometry from Keck/NIRC2. A joint fit of the available relative astrometry, radial velocities, and tangential astrometric acceleration yields a dynamical mass of $M_B$ = 0.609$^{+0.010}_{-0.011}$ $M_{\odot}$ for HD 159062 B, a semi-major axis of 60$^{+5}_{-7}$ AU, and preference for circular orbits ($e$$<$0.42 at 95% confidence). 12 Psc B and HD 159062 B join a small list of resolved "Sirius-like" benchmark white dwarfs with precise dynamical mass measurements which serve as valuable tests of white dwarf mass-radius cooling models and probes of AGB wind accretion onto their main-sequence companions.