Examining the Age/Activity Relationship of Ultracool Dwarfs with GAIA

TL;DR

This paper models how stellar flares in ultracool dwarfs can be detected by GAIA, estimating flare rates and the potential number of observable flares to understand age and activity relationships.

Contribution

It provides conversion estimates of flare magnitudes across different bands and predicts flare detection rates in GAIA for ultracool dwarfs, aiding age-activity studies.

Findings

Estimated GAIA flare rate for M0-M6 dwarfs is at least 8.73e-4 hr^-1 deg^-2.

Projected over the entire survey, over 20,000 flares from M0-M6 dwarfs could be detected.

Ultracool dwarfs (M7-L5) may produce over 20 detectable flares in GAIA data.

Abstract

The relationship between age, rotation, and magnetic activity can be used to roughly estimate the ages of solar-type stars. At lower stellar masses, the relationship between activity and age changes due to the less efficient angular momentum loss, and may disappear entirely for ultracool (late-M and L) dwarfs. The detection of flares (as a tracer of magnetic activity) can be combined with kinematic tracers of age to explore the relationship between age and activity for ultracool dwarfs. The final data release of GAIA will provide time-resolved photometry of GAIA targets in the $G$ filter, but the effect of flares in the $G$-band is not well understood. I use a simple flare model to estimate the conversion of flare magnitudes for M3--L5 dwarfs in the Johnson $V$-, SDSS $r$-, and Kepler- bands to the GAIA $G$-band. By applying those conversions to previously observed flare rates, I estimate that M0-M6 dwarfs will have a flare rate in GAIA of $R_{f,GAIA} \gtrsim 8.73 \times 10^{-4}~{\rm hr}^{-1}~{\rm deg}^{-2}$, corresponding to a total of $\gtrsim$20,000 flares in the whole survey. If ultracool dwarfs have the same flare rate, I would expect a total of $\gtrsim$20 flares on M7-L5 dwarfs.