A gas-dynamic model for a flare on YZ CMi: interpretation of high-temporal-resolution spectroscopic data

The spectra of a flare on YZ CMi, obtained with a temporal resolution of 60 s on 1985 March 4 over the wavelength range 3600-4400 A, are analysed using a gas-dynamic model. In this model, the optical radiation in the U band, outside of flare maximum, is produced by a condensation formed during the gas-dynamic process. The numerical modelling of such a process in the red-dwarf atmosphere shows that the source of the optical radiation is a dense, cool plasma with a small height. With the optical continuum described by a Planck function for a temperature of 104 K, the emitting source area is ≥5 x 1017 cm2. It is supposed that this source is responsible for the radiation from the higher Balmer lines when they are at their maximum intensity. (Author)