ON THE CYCLOTRON LINES IN GAMMA-RAY BURST SPECTRA

Transfer of radiation at cyclotron frequency harmonics in rarefield pl asma is considered with modes' conversion taken into account. The para meters of cyclotron lines, formed by electron-positron plasma slab abo ve the polar hot spot of a strongly magnetized neutron star, are deter mined analytically. The model of the cyclotron line formation in gamma -ray burst spectra is developed which allows to find the plasma parame ters in the line-forming region using the observed characteristics of the lines. For the bursts GB870303 and GB880205 seen by GINGA the magn etic field strength, plasma temperature, column density, angle between the magnetic field and the line of sight, and also the maximal distan ce to the source are determined. The results imply that the bursts con sidered am of the galactic origin.