Properties of Radiative Shock Waves in the Atmospheres of Red Dwarf Stars

• Published in: Astrophysics 2019-06, Vol.62 (2), p.234-250
• Main Authors: Belova, O. M., Bychkov, K. V.
• Format: Article
• Language: English
• Subjects: Astronomy; Astrophysics; Astrophysics and Astroparticles; Astrophysics and Cosmology; Atmosphere; Balmer series; Black body radiation; Blackbody; Bremsstrahlung; Calcium; Chemical elements; Dwarf stars; Elastic scattering; Emission; Energy flux; Energy transfer; Fluctuations; Fluxes; Heat exchange; Hydrogen; Magnesium; Observations; Observations and Techniques; Organic chemistry; Photosphere; Physics; Physics and Astronomy; Radiation; Red dwarf stars; Shock waves; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; Stellar atmospheres; Stellar flares
• ISSN: 0571-7256; 1573-8191
• DOI: 10.1007/s10511-019-09577-4

The emission from the gas behind the front of a stationary shock wave is calculated for the conditions in the atmospheres of red dwarf stars for velocities u 0 from 30 to 100 km/s. Energy exchange between the electron and atom-ion components is taken into account through elastic collisions, free-free, bound-bound, and bound-free collisional and radiative transitions of hydrogen in the radiation field of a star’s photosphere. Cooling by the following chemical elements is included: C, N, O, Mg, Si, S, Ca, and Fe. The following results are obtained: the post-shock gas remains transparent in the optical range of the continuum throughout the emission time; hence, it cannot be a source of the black-body radiation that appears at times during flares. The recombination and bremsstrahlung radiation of the transparent gas, as well as the flux in the Balmer series lines represent a few percent of the energy flux of matter through the viscous jump. The ratio of the fluxes in the spectrum lines and the continuum depends on u 0 and on the parameters of the atmosphere. These results are consistent with the idea of multicomponent emission in flares, specifically, line emission is determined by the shock wave in layers above the photosphere, while black-body radiation comes from the photosphere heated by a flux of suprathermal particles.