  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.
