On the Origin of Optical Radiation During the Impulsive Phase of Flares on dMe Stars. II. Continuum and Line Radiation

Abstract

It is argued that not only the blue (at the brightness maximum) but also the red (in the slow decay phase) components of the optical continuum of powerful flares on dMe stars are formed near the photosphere. The possible appearance of HeI lines in the relaxation zones for the plasma to a state of thermal equilibrium (as a result of a rise in electron temperature owing to elastic collisions of electrons with atoms and ions) is noted (for sufficiently high speeds of a non-stationary chromospheric shock wave propagating toward the photosphere of the Sun and stars). A scheme is proposed for the positioning of the "layers" of plasma responsible for the generation of radiation in the white light continuum during the impulsive phase of powerful stellar flares.

Time-dependent Stellar Flare Models of Deep Atmospheric Heating

“…However, the beam current densities may be too large to last during the propagation from the corona to the chromosphere. Further, electron-beam-generated chromospheric condensations (e.g., Livshits et al 1981;Fisher et al 1985;Fisher 1989;Gan et al 1992) in some of these models produce hydrogen Balmer line spectra that are too broad (Kowalski 2022); other recent perspectives and arguments have been provided by Belova & Bychkov (2019) and Morchenko (2020aMorchenko ( , 2020b. Stellar flare RHD models have considered smaller electron-beam heating fluxes, but the model Balmer jumps are larger than in all known spectral observations; the photosphere is radiatively backheated by this Balmer continuum radiation, which originates at chromospheric heights (Allred et al 2006).…”