Title: Characterization of TESS planet hosts with CHIRON PI: Sam Quinn Abstract ----------------------------------------------------------------------------------- NASA’s Transiting Exoplanet Survey Satellite (TESS) has begun its two-year prime mission to survey the sky for small planets transiting the nearest, brightest stars, which are ideal targets for determining masses and atmospheric properties using large ground-based and space-based facili- ties. Many candidates will turn out to orbit stars poorly suited for precise radial velocities, or to be eclipsing binaries masquerading as planets. It is crucial that reconnaissance spectroscopy be ob- tained to rule out such scenarios before devoting more precious observational resources. Moreover, the same spectroscopic observations used to assess the host stars can be used to address funda- mental questions of planet formation and evolution: improved stellar properties lead to improved planetary properties, which can reveal previously hidden characteristics of planetary populations; stellar metallicity can be compared to planetary properties and occurrence to understand the birth environment; and stellar rotational velocities reveal the orientation of angular momentum in the system, constraining the processes of planetary formation and evolution. We propose for 15 nights of CHIRON time to characterize TESS planet hosts and measure their radial velocities.