Companions to B/A Stars Snapshot (CBASS) Survey: B and A Star Stellar Ages from High-Resolution Spectra

The ongoing Companions to B/A Stars Snapshot (CBASS) survey is a direct-imaging demographics survey for wide-separation substellar companions to over 200 intermediate-mass stars in the northern sky. We present our method for calculating age posterior probability distributions for each of the target stars. By combining color-magnitude diagram position with measured vsini and [Fe/H], we derive model-based ages for the sample that are more accurate and precise than are possible from CMD position alone. We are obtaining high-resolution optical spectra from APO/ARCES for the B and A stars in the CBASS sample, and measuring of [Fe/H] and vsini for the survey sample from these spectra. We discuss how the inclusion of vsini and [Fe/H] measured from optical spectra improves the precision and accuracy of ages obtained from CMD position. Our analysis will enable robust, uniformly derived age posteriors and associated uncertainties for the sample, as well as other intermediate-mass stars. These reliable stellar sample ages are essential for direct-imaging planet search surveys, both for characterization of companions and for calculating survey completeness.