A single power law for the TRAPPIST-1 flare distribution across four orders of magnitude in energy

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 $\mathit{\text{Kepler}}$/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 ($T_{\mathrm{f}\mathrm{l}\mathrm{a}\mathrm{r}\mathrm{e}}=3500$,K). After correcting for flare-detection sensitivities, the combined JWST+K2 cumulative FFD is consistent with a single power law, $N(\ge E_{\mathrm{T}\mathrm{E}\mathrm{S}\mathrm{S}})\propto E_{\mathrm{T}\mathrm{E}\mathrm{S}\mathrm{S}}^{-\beta }$, with $\beta =0.753$ over $E_{\mathrm{T}\mathrm{E}\mathrm{S}\mathrm{S}}\simeq {10}^{29}$-${10}^{33}$,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 $E_{\mathrm{T}\mathrm{E}\mathrm{S}\mathrm{S}}>{10}^{32}$~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.