Continuum and Line Emission of Flares on Red Dwarf Stars: Origin of the Blue Continuum Radiation

TL;DR

This paper reviews models explaining blue continuum radiation in stellar flares on red dwarfs, clarifies misconceptions, and presents evidence that challenges previous claims about the origin of this emission.

Contribution

The paper critically evaluates existing models and demonstrates that the claim placing the white-light continuum source in the dense chromospheric region is incorrect.

Findings

The blue continuum originates in the transition layer between chromosphere and photosphere.

The dense chromospheric region is not the primary source of white-light continuum.

Previous models placing the continuum in the chromosphere are challenged.

Abstract

There are two types of models that explain the appearance of the quasi-blackbody radiation during the impulsive phase of stellar flares. Grinin and Sobolev [Astrophysics, Vol. 13, 348 (1977)] argue that the blue component of the optical continuum is formed in "the transition layer between the chromosphere and the photosphere." Katsova et al. [Astrophysics, Vol. 17, 156 (1981)] have "raised" the source of the white-light continuum up to a dense region in the perturbed chromosphere. In the present contribution (the main paper is published in "Astrophysics" [Vol. 59, 475 (2016); arXiv:1710.08008], we show that this statement in the work of Katsova et al. is erroneous.