Optical follow-up of GRB afterglows from UPSO, Naini Tal

Abstract

Successful optical photometric observations of five GRB afterglows namely GRB 990123, GRB 991208, GRB 991216, GRB 000301c and GRB 000926 have been carried out from State Observatory Naini Tal till 2000. The results and light curve parameters of these GRBs are summarised here. The optical light curves of these GRBs exhibit break (i.e., early and late time power law decay with different indices) generally around 2 days after the burst. The observed steepening in the afterglow light curves may be due to non-isotropic emission from the burst ejecta in the course of time. The non-isotropic energy emission from these GRBs is ≤10⁵² ergs and can be understood in terms of current popular models for the origin of GRBs.