Gravitational microlensing of gamma-ray bursts

A Monte Carlo code is developed to calculate gravitational microlensing in three dimensions when the lensing optical depth is low or moderate (<= 0.25). The code calculates positions of microimages and time delays between the microimages. Assuming the gamma-ray bursters are cosmological, and adopting {OMEGA}_0_ = 0.15 in massive black holes (~10^6.5^ M_sun_), as proposed by Gnedin & Ostriker, we find that the lensing probability is 5% for those gamma-ray bursts for which the brightest (primary) microimages will be detectable by the BATSE experiment on board the Compton Gamma-Ray Observatory, and for which at least one secondary image is brighter than 25% of the primary image. The majority (90%) of lensed gamma-ray bursts should show a simple double- burst structure, as predicted by a single point mass lens model. A small fraction (~10%) should show complicated multiple events due to the collective effects of several point masses (black holes). Cosmological models with a significant fraction of mass density in massive compact objects (M > 10^6^ M_sun_) can be tested by searching for microlensing events in the current BATSE data. Our catalog generated by 10,000 Monte Carlo models is accessible through the computer network. The catalog can be used to take realistic selection effects into account.