The Solar Neighborhood LI: A Variability Survey of Nearby M Dwarfs with Planets from Months to Decades with TESS and the CTIO/SMARTS 0.9 m Telescope

Abstract

We present the optical photometric variability of 32 planet-hosting M dwarfs within 25 pc over timescales of months to decades. The primary goal of this project—A Trail to Life Around Stars (ATLAS)—is to follow the trail to life by revealing nearby M dwarfs with planets that are also “quiet,” which may make them more amiable to habitability. There are 69 reported exoplanets orbiting the 32 stars discussed here, providing a rich sample of worlds for which environmental evaluations are needed. We examine the optical flux environments of these planets over month-long timescales for 23 stars observed by TESS, and find that 17 vary by less than 1% (∼11 mmag). All 32 stars are being observed at the CTIO/SMARTS 0.9 m telescope, with a median duration of 19.1 yr of optical photometric data in the VRI bands. We find over these extended timescales that six stars show optical flux variations less than 2%, 25 vary from 2% to 6% (∼22–67 mmag), and only one, Proxima Centauri, varies by more than 6%. Overall, LHS 1678 exhibits the lowest optical variability levels measured over all timescales examined, thereby providing one of the most stable photometric environments among the planets reported around M dwarfs within 25 pc. More than 600 of the nearest M dwarfs are being observed at the 0.9 m telescope in the RECONS program that began in 1999, and many more planet hosts will undoubtedly be revealed, providing more destinations to be added to the ATLAS sample in the future.