The TESS-Keck Survey. XXII. A sub-Neptune Orbiting TOI-1437

Exoplanet discoveries have revealed a dramatic diversity of planet sizes across a vast array of orbital 41 architectures. Sub-Neptunes are of particular interest; due to their absence in our own solar system, 42 we rely on demographics of exoplanets to better understand their bulk composition and formation 43 scenarios. Here, we present the discovery and characterization of TOI-1437 b, a sub-Neptune with a 44 18.84 day orbit around a near-Solar analog (M⋆ = 1.10 ± 0.10 M⊙, R⋆ = 1.17 ± 0.12 R⊙). The planet 45 was detected using photometric data from the Transiting Exoplanet Survey Satellite (TESS) mission 46 and radial velocity follow-up observations were carried out as a part of the TESS-Keck Survey (TKS) 47 using both the HIRES instrument at Keck Observatory and the Levy Spectrograph on the Automated 48 Planet Finder (APF) telescope. A combined analysis of these data reveal a planet radius of Rp = 2.24 2 ± 0.23 R⊕ and a mass measurement of 49 Mp = 9.6 ± 3.9 M⊕). TOI-1437 b is one of few (∼50) known 50 transiting sub-Neptunes orbiting a solar-mass star that has a radial velocity mass measurement. As the 51 formation pathway of these worlds remains an unanswered question, the precise mass characterization 52 of TOI-1437 b may provide further insight into this class of planet.