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White-light stellar flares are now reported by the thousands inlong-baseline, high precision, broad-band photometry from missions like Kepler,K2, and TESS. These observations are crucial inputs for assessments ofbiosignatures in exoplanetary atmospheres and surface ultraviolet radiationdosages for habitable zone planets around low-mass stars. A limitation of theseassessments, however, is the lack of near-ultraviolet spectral observations ofstellar flares. To motivate further empirical investigation, we use a grid ofradiative-hydrodynamic simulations with an updated treatment of the pressurebroadening of hydrogen lines to predict the $\lambda \approx 1800-3300$ \AA\continuum flux during the rise and peak phases of a well-studied superflarefrom the dM3e star AD Leo. These predictions are based on semi-empiricalsuperpositions of radiative flux spectra consisting of a high-flux electronbeam simulation with a large, low-energy cutoff ($\gtrsim 85$ keV) and alower-flux electron beam simulation with a smaller, low-energy cutoff($\lesssim 40$ keV). The two-component models comprehensively explain thehydrogen Balmer line broadening, the optical continuum color temperature, theBalmer jump strength, and the far-ultraviolet continuum strength and shape inthe rise/peak phase of this flare. We use spatially resolved analyses of solarflare data from the Interface Region Imaging Spectrograph, combined with theresults of previous radiative-hydrodynamic modeling of the 2014 Mar 29 X1 solarflare (SOL20140329T17:48), to interpret the two-component electron beam modelas representing the spatial superposition of bright kernels and fainter ribbonsover a larger area.

Near-Ultraviolet Continuum Modeling of the 1985 April 12 Great Flare of AD Leo