The TESS-Keck Survey. VIII. TOI-2180 radial velocity

This planet transited only once in Cycle 2 of the primary Transiting Exoplanet Survey Satellite (TESS) mission. Citizen scientists identified the 24hr single-transit event shortly after the data were released, allowing a Doppler monitoring campaign with the Automated Planet Finder telescope at Lick Observatory to begin promptly.

The radial velocity observations refined the orbital period of TOI-2180b to be 260.8{+/-}0.6days, revealed an orbital eccentricity of 0.368{+/-}0.007, and discovered long-term acceleration from a more distant massive companion. We conducted ground-based photometry from 14 sites spread around the globe in an attempt to detect another transit. Although we did not make a clear transit detection, the nondetections improved the precision of the orbital period.