On the cyclotron lines in gamma-ray burs spectra.

Radiation transfer at cyclotron harmonics in rarefied plasma is examined with allowance for the mutual conversion of normal modes. The parameters of spectral lines formed in a plane homogeneous layer of electron-positron plasma over the hot polar spot of a neutron star with a strong magnetic field are calculated analytically. A model describing the formation of cyclotron lines in the spectra of cosmic gamma-ray bursts is developed which makes it possible to determine the parameters of line-formation regions from the observed characteristics. For GB870303 and GB880205 bursts, recorded by the GINGA satellite, determinations are made of the magnetic field, plasma temperature, column density, angle between the magnetic field and the line of sight, and maximum distance to the source. The results indicate the galactic origin of the bursts.