wolffem / trappist_xuv

Improved Constraints for the XUV Luminosity Evolution of Trappist-1

Improved Constraints for the XUV Luminosity Evolution of Trappist-1

Jessica Birky, Rory Barnes, and David P. Fleming

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 on , we infer that TRAPPIST-1 maintained a saturated XUV luminosity, relative to the bolometric luminosity, of log(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 beta = -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 ~10^{30}-10^{32} erg} over the star's lifetime.

Code

Repositories

• Updated study: https://github.com/jbirky/trappist_xuv
• Original study: https://github.com/dflemin3/trappist

Dependencies

• vplanet (v1.2)
• vplot
• approxposterior
• george
• emcee

Repository guide

Main files:

mcmc/
    runAPMCMCTrappist1.py
    trappist1.py
    corner.ipynb
    
flux_calc/
    integratedFlux.ipynb

Usage:

• To reproduce the MCMC results with approxposterior, see runAPMCMCTrappist1.py
• To change the prior or likelihood assumptions for the model fitting, see trappist1.py
• To analyze the the the burned-in posterior samples, (from Figure 1 from this study) without re-running approxposterior, see corner.ipynb
• To reproduce the integrated flux calculations, see integratedFlux.ipynb