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

TL;DR

This paper investigates the origin of optical radiation during the impulsive phase of stellar flares on dMe stars, focusing on continuum and line formation near the photosphere and the role of shock waves.

Contribution

It proposes a new scheme for the plasma layers responsible for white light continuum radiation during stellar flares, emphasizing the role of shock waves and thermal equilibrium zones.

Findings

Both blue and red continuum components form near the photosphere.

HeI lines may appear in relaxation zones due to increased electron temperature.

A model scheme for plasma layer positioning during flares is proposed.

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.