Improved Constraints for the XUV Luminosity Evolution of Trappist-1

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 ${\log }_{10}$(L${}_{\mathrm{X}\mathrm{U}\mathrm{V}}$/L${\rm bol}$)$= -3.03{-0.23}^{+0.25}$atearlytimesforaperiodof$t_{sat} = 3.14_{-1.46}^{+2.22}$Gyr\mathrm{.}Afterthesaturationphase,wefindL${\rm XUV}$decayedovertimebyanexponentialrateof$\beta{\rm XUV} = -1.17_{-0.28}^{+0.27}$\mathrm{.}Comparedtoourinferredageofthesystem,${\rm age} = 7.96_{-1.87}^{+1.78}$Gyr,ourresultfor$t_{sat}$ suggests that there is only a $\sim 4\mathrm{\%}$~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 $t_{sat}$, 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 $\sim {10}^{30}-{10}^{32}$ erg over the star’s lifetime.