Constructing a Spectral Rubric for Estimating the Age and Activity of K Dwarfs within the Solar Neighborhood

Here we present the results of an ongoing spectroscopic study into the age and activity of 1,256 K dwarfs within 40 parsecs and between DEC +30 degrees and -30 degrees (Hostaris Sample). To complete this study, a calibration set of stars was assembled from nearby moving associations and open clusters with reliable age estimates (KYOUNG Sample). The sample includes stars from; β Pictoris moving group (20 Myr), the Tucana-Horologium association (40 Myr), AB Doradus moving group (120 Myr), and the Hyades cluster (700 Myr), along with nearby field K dwarfs with reliable age estimates(1.5-5 Gyr). The CHIRON echelle spectrometer on the SMARTS 1.5m telescope has been used to acquire high resolution (R= 80000) spectra for 701 of the 1256 Hostaris members and 53 stars in the KYOUNG sample. Of the four spectral indicators tested using the KYOUNG spectra, three showed trends that aligned with the estimated ages of the five sets of stars. Namely the Na I Doublet (5895.92 Å & 5889.95 Å), the Hα absorption line (6562.8 Å), and the Li I resonance line (6707.8 Å). When 2 subsets of the Hostaris sample (n ~ 100 stars) were tested against these 3 spectral indicators, we identified 3% of K dwarfs with an age estimate younger than 700 Myr and 5% with stellar activity unusual to older K dwarf field stars. Upon completion, this study will serve as a great resource to present and future studies of exoplanet habitability. This effort has been supported by the NSF through grant AST-1910130 via observations made possible by the SMARTS Consortium.