Evolution of Flare Activity in GKM Stars Younger than 300 Myr over Five Years of TESS Observations
arxiv(2024)
摘要
Stellar flares are short-duration (< hours) bursts of radiation associated
with surface magnetic reconnection events. Stellar magnetic activity generally
decreases as a function of both age and Rossby number, R_0, a measure of the
relative importance of the convective and rotational dynamos. Young stars
(<300 Myr) have typically been overlooked in population-level flare studies
due to challenges with flare-detection methods. Here, we select a sample of
stars that are members of 26 nearby moving groups, clusters, or associations
with ages <300 Myr that have been observed by the Transiting Exoplanet Survey
Satellite at 2-minute cadence. We identified 26,355 flares originating from
3,157 stars and robustly measure the rotation periods of 1,847 stars. We
measure and find the flare frequency distribution (FFD) slope, α,
saturates for all spectral types at α∼ -0.5 and is constant over 300
Myr. Additionally, we find that flare rates for stars t_age = 50 -
250 Myr are saturated below R_0 < 0.14, which is consistent with other
indicators of magnetic activity. We find evidence of annual flare rate
variability in eleven stars, potentially correlated with long term stellar
activity cycles. Additionally, we cross match our entire sample with GALEX and
find no correlation between flare rate and Far- and Near-Ultraviolet flux.
Finally, we find the flare rates of planet hosting stars are relatively lower
than comparable, larger samples of stars, which may have ramifications for the
atmospheric evolution of short-period exoplanets.
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