TP-10

Afterglow lightcurves from beamed outflows

Agnieszka Majczyna (Warsaw University) Tomasz Bulik (Copernicus Center, Poland) Rafal Moderski (University of Colorado) Marek Sikora (Copernicus Center, Poland)

Using the numerical code (Moderski, Sikora, Bulik; 1999) we calculate the lightcurves of gamma-ray burst afterglows. We analyze the dependence on the initial Lorentz factor, the collimation angle , the location of the observer, and including the lateral outflow of the expanding shell. We discuss the results in the framework of recently observed gamma-ray bursts (GRB990123 and GRB990510).