BAFFLES: Bayesian Ages for Field Lower-Mass Stars

Abstract

Age is a fundamental parameter of stars, yet in many cases ages of individual stars are presented without robust estimates of the uncertainty. We have developed a Bayesian framework, BAFFLES, to produce the age posterior for a star from its calcium emission strength (log($R_{HK}^{\prime }$)) or lithium abundance (Li EW) and $B-V$ color. We empirically determine the likelihood functions for calcium and lithium as functions of age from literature measurements of stars in benchmark clusters with well-determined ages. We use a uniform prior on age which reflects a uniform star formation rate. The age posteriors we derive for several test cases are consistent with literature ages found from other methods. BAFFLES represents a robust method to determine the age posterior probability distribution for any field star with $0.45\le B-V\le 0.9$ and a measurement of $R_{HK}^{\prime }$ and/or $0.35\le B-V\le 1.9$ and measured Li EW. We compile colors, $R_{HK}^{\prime }$, and Li EW from over 2630 nearby field stars from the literature and present the derived BAFFLES age posterior for each star.

Accepted to ApJ, 80 pages, 14 figures, 3 tables

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