  The 1RXS J034231.8+121622 system consists of an M dwarf primary and a
directly imaged low-mass stellar companion. We use high resolution
spectroscopic data from Keck/KPIC to estimate the objects' atmospheric
parameters and radial velocities (RVs). Using PHOENIX stellar models, we find
that the primary has a temperature of 3460 $\pm$ 50 K a metallicity of 0.16
$\pm$ 0.04, while the secondary has a temperature of 2510 $\pm$ 50 K and a
metallicity of $0.13\substack{+0.12 \\ -0.11}$. Recent work suggests this
system is associated with the Hyades, placing it an older age than previous
estimates. Both metallicities agree with current $[Fe/H]$ Hyades measurements
(0.11 -- 0.21). Using stellar evolutionary models, we obtain significantly
higher masses for the objects, of 0.30 $\pm$ 0.15 $M_\odot$ and 0.08 $\pm$ 0.01
$M_\odot$ (84 $\pm$ 11 $M_{Jup}$) respectively. Using the RVs and a new
astrometry point from Keck/NIRC2, we find that the system is likely an edge-on,
moderately eccentric ($0.41\substack{+0.27 \\ -0.08}$) configuration. We also
estimate the C/O ratio of both objects using custom grid models, obtaining 0.42
$\pm$ 0.10 (primary) and 0.55 $\pm$ 0.10 (companion). From these results, we
confirm that this system most likely went through a binary star formation
process in the Hyades. The significant changes in this system's parameters
since its discovery highlight the importance of high resolution spectroscopy
for both orbital and atmospheric characterization of directly imaged
companions.
