  Exoplanet discoveries have revealed a dramatic diversity of planet sizes
across a vast array of orbital architectures. Sub-Neptunes are of particular
interest; due to their absence in our own solar system, we rely on demographics
of exoplanets to better understand their bulk composition and formation
scenarios. Here, we present the discovery and characterization of TOI-1437 b, a
sub-Neptune with a 18.84 day orbit around a near-Solar analog (Mstar = 1.10 +/-
0.10 Msun, Rstar = 1.17 +/- 0.12 Rsun). The planet was detected using
photometric data from the Transiting Exoplanet Survey Satellite (TESS) mission
and radial velocity follow-up observations were carried out as a part of the
TESS-Keck Survey (TKS) using both the HIRES instrument at Keck Observatory and
the Levy Spectrograph on the Automated Planet Finder (APF) telescope. A
combined analysis of these data reveal a planet radius of Rp = 2.24 +/- 0.23
Rearth and a mass measurement of Mp = 9.6 +/- 3.9 Mearth). TOI-1437 b is one of
few (~50) known transiting sub-Neptunes orbiting a solar-mass star that has a
radial velocity mass measurement. As the formation pathway of these worlds
remains an unanswered question, the precise mass characterization of TOI-1437 b
may provide further insight into this class of planet.
