Knowledge Bank

This thesis serves as a project report on an effort to analyze spectroscopic rotation rates of field stars and low-mass stars in the Alpha Persei open cluster to extract information about stellar ages from spectroscopic measures alone. A sample of unevolved G and K field dwarfs from Kim et al. (2016), of which we have high-resolution spectra, is combined with two large spectroscopic surveys from Brewer et al. (2016) and Buder et al. (2019) to explore three indicators of youth -- rotation, lithium abundance, and kinematics. The stars chosen for the analysis reside on the main sequence below the luminosities where isochrone fitting can determine stellar ages. However, using parallaxes and proper motions retrieved from Gaia DR2, we show that, regardless of the selection methods in these samples, stars with detectable projected rotation (> 6 km/s) and lithium abundances are members of kinematically cold populations as expected of young stars. Using stellar evolution models from Denissenkov et al. (2010), we show that, with 90% confidence, a probabilistic upper limit for age may be assigned to a star with a given rotation rate. We pay particular attention to the effect of binarity and uncertainties in v sin i on the calculation of the age posteriors. We demonstrate errors in v sin i are not significant compared to the effects of inclination angle except when v sin i is at or near the detection limit. Finally, we discuss how well this method can be implemented to identify the youngest exoplanet host stars from spectra alone.