Author: Gennady S. Bisnovatyi-Kogan
Abstract: Observations of bright optical GRB afterglows point to the fact that an initially bright optical flare is directly related to the GRB itself, and the subsequent weak and much more continuous optical radiation is of a different nature. The interaction of the cosmological GRB radiation with a dense surrounding molecular cloud results in the appearance of long-duration (up to 10 years) weak optical afterglows associated with the heating and reradiation of gas. Results of 2D numerical simulation of the heating and reradiation of gas in various variants of the relative dispositionof GRB and molecular clouds are presented. The possible relation between the short GRBs and soft gamma repeaters (SGR) is discussed. The model of SGR activity, based on nuclear explosion in the nonequilibrium layer in the neutron star crust, is discussed.