The Role of a Neutron Component in the Photospheric Emission of Long-Duration Gamma-Ray Burst Jets

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Auteurs principaux: Walker, Nathan, Parsotan, Tyler, Lazzati, Davide
Format: Preprint
Publié: 2024
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author Walker, Nathan
Parsotan, Tyler
Lazzati, Davide
author_facet Walker, Nathan
Parsotan, Tyler
Lazzati, Davide
contents Long-duration gamma-ray bursts (LGRBs), thought to be produced during core-collapse supernovae, may have a prominent neutron component in the outflow material. If present, neutrons can change how photons scatter in the outflow by reducing its opacity, thereby allowing the photons to decouple sooner than if there were no neutrons present. Understanding the details of this process could therefore allow us to probe the central engine of LGRBs, which is otherwise hidden. Here, we present results of the photospheric emission from an LGRB jet, using a combination of relativistic hydrodynamic simulations and radiative transfer post-processing using the Monte Carlo Radiation Transfer (MCRaT) code. We control the size of the neutron component in the jet material by varying the equilibrium electron fraction $Y_{e}$, and we find that the presence of neutrons in the GRB fireball affects the Band parameters $α$ and $E_{0}$, while the picture with the $β$ parameter is less clear. In particular, the break energy $E_{0}$ is shifted to higher energies. Additionally, we find that increasing the size of the neutron component also increases the total radiated energy of the outflow across multiple viewing angles. Our results not only shed light on LGRBs, but are also relevant to short-duration gamma-ray bursts associated with binary neutron star mergers, due to the likelihood of a prominent neutron component in such systems.
format Preprint
id arxiv_https___arxiv_org_abs_2402_18657
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle The Role of a Neutron Component in the Photospheric Emission of Long-Duration Gamma-Ray Burst Jets
Walker, Nathan
Parsotan, Tyler
Lazzati, Davide
High Energy Astrophysical Phenomena
Long-duration gamma-ray bursts (LGRBs), thought to be produced during core-collapse supernovae, may have a prominent neutron component in the outflow material. If present, neutrons can change how photons scatter in the outflow by reducing its opacity, thereby allowing the photons to decouple sooner than if there were no neutrons present. Understanding the details of this process could therefore allow us to probe the central engine of LGRBs, which is otherwise hidden. Here, we present results of the photospheric emission from an LGRB jet, using a combination of relativistic hydrodynamic simulations and radiative transfer post-processing using the Monte Carlo Radiation Transfer (MCRaT) code. We control the size of the neutron component in the jet material by varying the equilibrium electron fraction $Y_{e}$, and we find that the presence of neutrons in the GRB fireball affects the Band parameters $α$ and $E_{0}$, while the picture with the $β$ parameter is less clear. In particular, the break energy $E_{0}$ is shifted to higher energies. Additionally, we find that increasing the size of the neutron component also increases the total radiated energy of the outflow across multiple viewing angles. Our results not only shed light on LGRBs, but are also relevant to short-duration gamma-ray bursts associated with binary neutron star mergers, due to the likelihood of a prominent neutron component in such systems.
title The Role of a Neutron Component in the Photospheric Emission of Long-Duration Gamma-Ray Burst Jets
topic High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2402.18657