RESEARCH
Monte Carlo Radiation Transfer through Gamma Ray Bursts
The left panel of the video shows photons, in red, being injected into and propagating through a Gamma Ray Burst outflow, plotted in purple/blue. The top right panel shows how the spectrum of those photons change as the photons interact with the matter in the jet. The bottom right panel shows the average temperatures of the photons, in red, and the matter surrounding the photons, in blue.
The video shown above shows a MCRaT radiative transfer simulation in which photons are injected into a Gamma Ray Burst outflow and then individually scatter and propagate each photon until the end of the outflow becomes optically thin and the photons ideally escape. The spectrum of those photons changes as they continually interact with the matter in the jet. Additionally, as the photons propagate through the expanding jet, the coupling between the counterparts of the jet gradually decrease. This is shown in the plot of the photon and matter temperatures.
The fluid properties of the GRB outflow are acquired from a hydrodynamic simulation of a Gamma Ray Burst jet propagating through some progenitor medium and my MCRaT code allows the photons to interact with the fluid thus allowing us to investigate how a realistic jet outflow affects the produced Gamma Ray Burst spectrum. This is integral to understanding the entirety of Gamma Ray Burst prompt emission.
We have primarily applied the MCRaT code to the analysis of special relativistic hydrodynamic simulations of Gamma Ray Bursts with a constant supply of energy, as seen in the video above, and simulations where the energy supplied to the jet is variable. Both analyses have already provided a better starting point from which we can compare simulations to observations and get a refined idea of how simulations need to be improved in order to better match nature.
An additional improvement that we have recently made is the inclusion of cyclo-synchrotron absorption and emission into the code. The presentation that I gave at the 16th Marcel Grossman Conference outlines this improvement and some of the results that we have acquired from our updated MCRaT code. See the youtube video below.
The results that I have acquired using MCRaT are contained in a number of papers that I have written. More information can be found on my CV.
MCRaT is hosted on GitHub at: github.com/lazzati-astro/MCRaT.
Additionally, the python package ProcessMCRaT which is used to analyze the results of a MCRaT simulation is hosted on github at: https://github.com/parsotat/ProcessMCRaT.
Future work will include subphotospheric shock physics in the Gamma Ray Burst as well as applying our radiative transfer analysis to Short Gamma Ray Bursts. Additionally, these MCRaT simulations will be used as the starting point for full forward modeling of GRB events observed various detectors.
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