Gamma-ray burst studies using spectro-polarimetry

The spectroscopic study of the prompt emission of GRBs alone is inadequate to discriminate between the models. Thus, one more constraining observable, polarisation, is of great importance for unravelling the emission mechanism and  is an emerging hot topic. Cadmium zinc telluride Imager (CZTI) onboard AstroSat is actively measuring polarisation in hard X-rays. In this talk, the novel technique of spectro-polarimetry will be presented for understanding the science of GRBs. The joint observations from AstroSat, Fermi and Swift have been utilised for understanding the observed emission mechanism in GRBs. Time-resolved spectro-polarimetric studies of a few bright GRBs reveal variation in the polarisation with a concurrent change in spectrum and will be detailed. The composite modelling of the spectrum, polarisation and afterglow observations of GRBs have been utilised for understanding the nature of the outflow.