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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 theVRIbands. 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. 

Abstract The introduction of the Rossby number (R₀), which incorporates the convective turnover time (τ), in 1984 was a pioneering idea for understanding the correlation between stellar rotation and activity. The convective turnover time, which cannot be measured directly, is often inferred using existingτ–mass orτ–color relations, typically established based on an ensemble of different types of stars by assuming thatτis a function of mass. In this work, we use Gaia Early Data Release 3 to demonstrate that the masses used to establish one of the most citedτ-mass relations are overestimated for G-type dwarfs and significantly underestimated for late M dwarfs, offsets that affect studies using thisτ–mass relation to draw conclusions. We discuss the challenges of creating such relations then and now. In the era of Gaia and other large data sets, stars used to establish these relations require characterization in a multidimensional space, rather than via the single-characteristic relations of the past. We propose that new multidimensional relations should be established based on updated theoretical models and all available stellar parameters for different interior structures from a set of carefully vetted single stars, so that the convective turnover time can be estimated more accurately.