Heating of the Circumstellar Medium by Gamma-Ray Burst Prompt Emission

We describe the technique and results of our numerical simulation of the effects related to the heating of the circumstellar medium by hard gamma-ray burst radiation using a modified STELLA radiation-hydrodynamics code. The code modification allows the processes of nonstationary heating and change in the state of the matter to be taken into account. We present the computed light curves and emergent gamma-ray, X-ray, and optical spectra for several models of the circumstellar medium (shells) with different geometrical sizes, densities, density profiles, chemical compositions, and temperatures. Depending on the model parameters, the total thermal and optical luminosities of the heated shell can reach 10(47) and 10(43) erg s(-1), respectively. The presence of bumps in the X-ray and optical GRB afterglow light curves can be explained by such effects.