Transit Hunt for Young and Maturing Exoplanets (THYME). VIII. A Pleiades-age Association Harboring Two Transiting Planetary Systems from Kepler

Abstract Young planets provide a window into the early stages and evolution of planetary systems. Ideal for such research are in coeval associations, where parent population can precisely determine their ages. We describe young association (MELANGE-3) Kepler field, which harbors two transiting systems (KOI-3876 Kepler-970). identify MELANGE-3 by searching kinematic spatial overdensities around planet hosts with high levels lithium. To age membership MELANGE-3, we combine new high-resolution spectra archival light curves, velocities, astrometry stars near KOI-3876 spatially kinematically. use resulting rotation sequence, lithium levels, color–magnitude diagram candidate members to confirm presence 105 ± 10 Myr population. may be part recently identified Theia 316 stream. For exoplanet systems, revise stellar parameters, taking account newly determined age. Fitting 4.5 yr find that KOI-3876b is 2.0 0.1 R ⊕ on 19.58 day orbit, while Kepler-970 b 2.8 0.2 16.73 orbit. was previously flagged as an eclipsing binary, rule out using radial velocities from APOGEE statistically validate signal origin. Given its overlap valuable studies spot year timescales, both contribute growing work associations.