Papers › Using the Gaia excess uncertainty as a proxy for stellar variability and age
Using the Gaia excess uncertainty as a proxy for stellar variability and age
Madyson G. Barber, Andrew W. Mann
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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 (Var_G, Var_(BP), and Var_(RP)) 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 Var 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 Var 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.
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