Dust Echoes from Gamma-Ray Bursts.
The deviation from the power-law decline of the optical flux observed in GRB 970228 and GRB 980326 has been used recently to argue in favor of the connection between gamma-ray bursts and supernovae. We consider an alternative explanation for this phenomenon, based on the scattering of a prompt optical burst by 0.1 M middle dot in circle dust located beyond its sublimation radius 0.1-1 pc from the burst. In both cases, the optical energy observed at the time of the first detection of the afterglow suffices to produce an echo after approximately 20-30 days, as observed. Prompt optical monitoring of future bursts and multiband photometry of the afterglows will enable us to test simple models of dust reprocessing quantitatively and to predict source redshift.
Esin
AA
Blandford
R