Role of THESEUS in Understanding the Radiation Mechanism of GRB Prompt Emission

Abstract

The radiation process of GRB prompt emission remains highly debated till date. Though a smoothly broken powerlaw function like Band provides an excellent fit to most of the cases, a spectrum with a broad top or double hump structure has emerged recently for several GRBs, specifically for the bright ones that have high signal to noise data. A number of models have been proposed to capture this shape which includes an additional blackbody component along with the Band, or a double smoothly broken powerlaw, or two blackbodies with a powerlaw/cut-off powerlaw and so on. However, finding the statistically favourable model has not always been possible primarily due to the limited resolution of GRB detectors. Recently, we have identified a number of interesting cases where an observation with focusing detectors are available at a later part of the prompt emission. Their high resolution data helped in identifying additional spectral component (a blackbody) in lower energies. The proposed THESEUS mission, with its unprecedented sensitivity and spectral resolution available from the very beginning of the prompt emission holds the key to identify the correct spectral model and thereby the radiation process.