http://arxiv.org/abs/2105.06505
A complete understanding of Gamma Ray Bursts (GRBs) has been difficult to achieve due to our incomplete knowledge of the radiation mechanism that is responsible for producing the prompt emission. This emission, which is detected in the first tens of seconds of the GRB, is typically dominated by hard X-ray and gamma ray photons although, there have also been a few dozen prompt optical detections. These optical detections have the potential to discriminate between plausible prompt emission models, such as the photospheric and synchrotron shock models. In this work we use an improved MCRaT code, which includes cyclo-synchrotron emission and absorption, to conduct radiative transfer calculations from optical to gamma ray energies under the photospheric model. The calculations are conducted using a set of two dimensional relativistic hydrodynamic long GRB jet simulations, consisting of a constant and variable jet. We find that correlations between the optical and gamma ray light curves can provide insight into the observer viewer angle as well as the variability of GRB jets. Furthermore, we find that there should be optical prompt precursors that precedes the main gamma ray emission for observers located far from the jet axis. Additionally, the detected optical emission originates from dense regions of the outflow such as shock interfaces and the jet-cocoon interface. These results show the importance of conducting global radiative transfer simulations using hydrodynamically calculated jet structures as well as the potential information that optical prompt detections can provide on GRB jets under the photospheric model.
T. Parsotan and D. Lazzati
Mon, 17 May 21
39/55
Comments: 22 pages, with 5 pages for the appendix; 11 figures; submitted to ApJ, comments welcome; the MCRaT code is open source and available at: this https URL and the ProcessMCRaT code is also open source and available at: this https URL
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