Speaker
Description
The radiation mechanisms powering Gamma-ray bursts (GRBs) and the physical processes shaping their relativistic jets remain one of the unresolved questions in high-energy astrophysics. Spectro-polarimetric observations of exceptionally bright GRBs offer a promising pathway to address these challenges. GRB 230307A, the second-brightest long GRB ever detected, with an isotropic gamma-ray energy release of 4.49 × 10 52 erg, is uniquely associated with a Kilonova,providing a rare opportunity to probe the radiation mechanisms of GRBs originating from compact object mergers. Here, we present a comprehensive time-resolved spectro-polarimetric analysis of GRB 230307A using joint observations from the AstroSat Cadmium Zinc Telluride Imager (CZTI), the Fermi Gamma-ray Burst Monitor (GBM) and Konus-Wind. Our analysis indicates the low energy spectral index α follows a hard-to-soft trend. Time-resolved polarization analysis indicates a change from low to high polarization fractions in the latter path of the burst. This evolution suggests a transition in the radiative process from thermal-dominated emission (unpolarized or weakly polarized) to non-thermal synchrotron emission (potentially high polarized). This transition provides critical insights into the role of magnetic
fields in shaping GRB emission and jet dynamics.
