Apache Point Observatory Follow-up of ACcelerating Candidate ExopLanet Host Stars (APO ACCELS): Ages for 166 Accelerating Stars in the Northern Hemisphere

Abstract Directly imaged substellar companions with well-constrained ages and masses serve as vital empirical benchmarks for planet formation and evolution models. Potential benchmark companions can be identified from astrometric accelerations of their host stars. We use Gaia DR3 and Hipparcos astrometry to identify 166 northern hemisphere stars with astrometric accelerations consistent with a substellar companion between 0 . ″ 5 and 1″. For this accelerating sample we identify young stars using Apache Point Observatory/ARCES spectra and TESS light curves. From spectroscopic screening of the sample, we measure ages for 24 stars with detectable amounts of lithium, place lower age limits on 135 stars with lithium nondetections, and measure ages from R H K ′ for 34 stars. A total of 129 stars have TESS light curves, from which we measure ages for 20 stars with rotation rates <15 days, and we identify three eclipsing binaries. We present median ages and confidence intervals of age posteriors for the entire sample and discuss how the overall age distribution of our sample compares to a uniform star formation rate in the solar neighborhood. We identify 47 stars with median ages <2 Gyr, 31 stars with median ages <1 Gyr, and 14 stars with median ages <0.5 Gyr, making them high-priority targets for direct imaging follow-up.