Infrared Afterglow of the Gamma Ray Burst GRB041219 as the Result of Reradiation from Dust in a Circumstellar Cloud

Observations of the afterglows of gamma ray bursts (GRBs) in different spectral ranges yield valuable information both about the nature of GRBs and about the properties of the surrounding medium. A powerful infrared (IR) afterglow has been observed at the site of the strong GRB041219. Here we interpret the observed IR afterglow as the result of a reprocessing of gamma radiation on dust in a cloud surrounding the GRB source. In this model we do not expect the appearance of a prompt optical afterglow which should be absorbed by the surrounding dust cloud. We estimate the collimation angle of the gamma radiation and obtain limits on the red shift (distance to the GRB source) by matching the model parameters to the experimental data.__________Translated from Astrofizika, Vol. 48, No. 3, pp. 439–444 (August 2005).