Using the Gaia excess uncertainty as a proxy for stellar variability and age

Madyson G. Barber; Andrew W. Mann

doi:10.3847/1538-4357/ace044

paper

Using the Gaia excess uncertainty as a proxy for stellar variability and age

arXiv:2302.09084 · doi:10.3847/1538-4357/ace044

Abstract

Stars are known to be more active when they are young, resulting in a strong correlation between age and photometric variability. The amplitude variation between stars of a given age is large, but the age-variability relation becomes strong over large groups of stars. We explore this relation using the excess photometric uncertainty in Gaia photometry ( $V a r_{G}$ , $V a r_{B P}$ , and $V a r_{R P}$ ) as a proxy for variability. The metrics follow a Skumanich-like relation, scaling as $≃ t^{- 0.4}$ . By calibrating against a set of associations with known ages, we show how $V a r$ of population members can predict group ages within 10-20% for associations younger than $≃$ 2.5 Gyr. In practice, age uncertainties are larger, primarily due to finite group size. The index is most useful at the youngest ages ( $<$ 100 Myr), where the uncertainties are comparable to or better than those derived from a color-magnitude diagram. The index is also widely available, easy to calculate, and can be used at intermediate ages where there are few or no pre- or post-main-sequence stars. We further show how $V a r$ can be used to find new associations and test if a group of co-moving stars is a real co-eval population. We apply our methods on the Theia groups within 350 pc and find $≳$ 90% are inconsistent with drawing stars from the field and $≃$ 80% have variability ages consistent with those derived from the CMD. Our finding suggest the great majority of these groups contain real populations.

arXiv commentAccepted to ApJ. 19 pages, 9 figures, 3 tables. For associated code, see https://github.com/madysonb/EVA

Using the Gaia excess uncertainty as a proxy for stellar variability and age

Abstract

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