Kavli Affiliate: Sara Seager
| Summary:
TRAPPIST-1 is an ultra-cool dwarf that flares frequently. These flares shape the surrounding planets’ high-energy irradiation environments, with consequences for atmospheric chemistry and escape, and they can contaminate transmission spectroscopy of those planets. A quantitative flare-frequency distribution (FFD) spanning the full energy range is therefore essential for both interpreting JWST spectra and modeling the planets’ irradiation histories. Here we present a unified FFD over four orders of magnitude in energy by jointly analyzing $approx$87,hr of JWST/NIRISS and JWST/NIRSpec time-series spectroscopy together with $approx$74,days of textitKepler/K2 photometry. To enable a consistent comparison across these heterogeneous datasets, we convert all events to energies in the TESS bandpass. For the Kepler-to-TESS conversion we adopt a cooler flare continuum appropriate for ultra-cool dwarfs ($T_rm flare=3500$,K). After correcting for flare-detection sensitivities, the combined JWST+K2 cumulative FFD is consistent with a single power law, $N(ge E_mathrmTESS)propto E_mathrmTESS^-β$, with $β=0.753$ over $E_rm TESSsimeq10^29$-$10^33$,erg. The slope of the distribution indicates that the time-averaged flare energy budget is dominated by rare, high-energy events rather than by the more numerous low-energy flares. Moreover, we found that strong flares with energies $E_mathrmTESS > 10^32$~erg occur once every 25 days, about an order of magnitude more frequently than inferred from previous TRAPPIST-1/analog FFD estimates. This elevated rate of energetic flares has important implications for atmospheric escape, photochemistry, and habitability assessments of the TRAPPIST-1 planets.
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