A Characterized TESS Stellar Rotation Pipeline for Young Stellar Association Membership Analysis

Jonathan Bush

Studies of planetary evolution using exoplanets rely on precise age dating of the host star to place the planetary systems on an evolutionary timeline. While determining the age of a single star is difficult, identifying the exoplanet host star as part of a stellar association enables a precise age estimate based on the group’s ensemble properties.  We can find loose associations around seemingly lonely exoplanets using the abundance of precise astrometry from Gaia and modern neighbor search methods, but we need to clean candidate membership lists of non-members that can skew the age estimate. Because stars lose angular momentum over time, stellar rotation is an indicator of group membership that is independent of kinematic group search methods. I present a pipeline to measure stellar rotation periods for any star from Causal Pixel Model lightcurves extracted from the TESS Full Frame Images for the purpose of analyzing the membership of young stellar associations. I used this pipeline to confirm that seven young exoplanetary systems and one brown dwarf are members of larger stellar populations. I quantify the completeness and reliability of the pipeline using the K2-TESS overlap sample of stars, comparing TESS rotations to ~23,000 rotations measured from K2 lightcurves in the Reinhold and Hekker (2020) catalog. I find that TESS rotation periods are reliable ~86% of the time out to 10 days, while TESS will miss fewer than one-third of rotators faster than 10 days. In the future, the pipeline can be used to make membership decisions for young stellar associations and to make estimates of non-member contamination rates.

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