We re-examine the XUV luminosity evolution of TRAPPIST-1 utilizing new observational constraints (XUV and bolometric luminosity) from multi-epoch X-ray/UV photometry. Following the formalism presented in Fleming et al. (2020), we infer that TRAPPIST-1 maintained a saturated XUV luminosity, relative to the bolometric luminosity, of log10(LXUV/Lbol) =−3.03−0.23+0.25 at early times for a period of tsat=3.14−1.46+2.22 Gyr. After the saturation phase, we find LXUV decayed over time by an exponential rate of βXUV=−1.17−0.28+0.27. Compared to our inferred age of the system, age=7.96−1.87+1.78 Gyr, our result for tsat suggests that there is only a ∼4%~chance that TRAPPIST-1 still remains in the saturated phase today, which is significantly lower than the previous estimate of 40\%. Despite this reduction in tsat, our results remain consistent in the conclusion that the TRAPPIST-1 planets likely received an extreme amount XUV energy -- an estimated integrated XUV energy of ∼1030−1032 erg over the star's lifetime.
@article{arxiv.2105.12562,
title = {Improved Constraints for the XUV Luminosity Evolution of Trappist-1},
author = {Jessica Birky and Rory Barnes and David P. Fleming},
journal= {arXiv preprint arXiv:2105.12562},
year = {2021}
}