2025ApJ...994L..31H

Although TRAPPIST-1's temperate planets have the highest transmission signals of any known system, flares contaminate 50%-70% of transits at the 1000 ppm level, far above 100 ppm secondary atmospheric signals. Efforts to mitigate flare contamination and assess impacts on radiation environments are each hampered by a lack of empirical spectral analysis and physics-based modeling. We present spectrotemporal analysis and radiative-hydrodynamic modeling of 5.5 hr of NIRISS and NIRSpec observations of six TRAPPIST-1 flares of 2.2-8.7 × 10³⁰ erg. The flare lines and continua are characterized using grid searches of RADYN beam-heating models spanning 10⁴ times in electron beam parameters. Best-fit models indicate these flares result from moderate-intensity beams with emergent electron fluxes of F_e = 10¹² erg s^–1 cm^–2 and energies ≤37 keV, although all models overpredict the Paschen jump. These models predict X-ray and extreme UV (XUV), far-UV, and near-UV counterparts to the IR peak fluxes of 8.9-28.9 × 10²⁷, 4.3-13.9 × 10²⁶, and 3.4-11.4 × 10²⁷ erg s^–1, respectively. Scaling the flare rate into the XUV suggests flaring contributes 1.35${}_{-0.15}^{+2.0}\,\times $ quiescence yr^–1. We bin integrations of similar flare effective temperature to construct fiducial flare spectra from 2000 to 4500 K, in order to develop separate empirical and RADYN-based mitigation pipelines. Both pipelines are applied to all 5.5 hr of R = 10 data, resulting in maximum residuals from 1 to 2.8 μm of 100-140 ppm and typical residuals of 54 ± 14 and 65 ± 17 ppm for the empirical and RADYN-based pipelines, respectively. Injection testing supports a 3σ detection capability for CO₂ atmospheres with features of 150-250 ppm, with weak evidence (Bayes factor ≈ 3) still obtained at 130 ppm. Our results motivate multiwavelength observations to improve model fidelity and test high-energy predictions.