The Photospheric Emission of a Short-Duration Gamma-Ray Burst Emerging from a Realistic Binary Neutron Star Merger

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Autori principali: Walker, Nathan, Lazzati, Davide, Parsotan, Tyler, Perna, Rosalba
Natura: Preprint
Pubblicazione: 2025
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author Walker, Nathan
Lazzati, Davide
Parsotan, Tyler
Perna, Rosalba
author_facet Walker, Nathan
Lazzati, Davide
Parsotan, Tyler
Perna, Rosalba
contents The almost simultaneous detection of GRB170817A and GW170817 ushered in nearly a decade of interest in binary neutron star mergers and their multi-messenger signals, resulting in a greater understanding of the processes that produce short-duration gamma-ray bursts and gravitational waves. However, open questions remain regarding the emission mechanism of these bursts. In this work we present results from the first study of an electromagnetic signal produced from a realistic treatment of a binary neutron star merger, both for on-axis and off-axis observations. We accomplish this by using the PLUTO hydrodynamical code to inject a relativistic jet into the ejecta of a realistic binary neutron star merger, which was itself obtained from the simulation of a 3D BNS merger. Then, we model the prompt photospheric emission that would emerge from this jet using the MCRaT radiative transfer code. We find that the resulting photon spectra can peak around ~1 MeV for on-axis emission and falls off noticeably for off-axis observations. We also find distinctly non-thermal low and high-energy tails in multiple observations, ranging from shallow to mid-off axis observations. Our on-axis results are consistent with the Amati Correlation for short bursts, with some strain evident at higher observing angles. Finally, we find that the radiative efficiency is much lower than seen in previous studies of the photospheric emission of long-duration gamma-ray bursts.
format Preprint
id arxiv_https___arxiv_org_abs_2509_12505
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The Photospheric Emission of a Short-Duration Gamma-Ray Burst Emerging from a Realistic Binary Neutron Star Merger
Walker, Nathan
Lazzati, Davide
Parsotan, Tyler
Perna, Rosalba
High Energy Astrophysical Phenomena
The almost simultaneous detection of GRB170817A and GW170817 ushered in nearly a decade of interest in binary neutron star mergers and their multi-messenger signals, resulting in a greater understanding of the processes that produce short-duration gamma-ray bursts and gravitational waves. However, open questions remain regarding the emission mechanism of these bursts. In this work we present results from the first study of an electromagnetic signal produced from a realistic treatment of a binary neutron star merger, both for on-axis and off-axis observations. We accomplish this by using the PLUTO hydrodynamical code to inject a relativistic jet into the ejecta of a realistic binary neutron star merger, which was itself obtained from the simulation of a 3D BNS merger. Then, we model the prompt photospheric emission that would emerge from this jet using the MCRaT radiative transfer code. We find that the resulting photon spectra can peak around ~1 MeV for on-axis emission and falls off noticeably for off-axis observations. We also find distinctly non-thermal low and high-energy tails in multiple observations, ranging from shallow to mid-off axis observations. Our on-axis results are consistent with the Amati Correlation for short bursts, with some strain evident at higher observing angles. Finally, we find that the radiative efficiency is much lower than seen in previous studies of the photospheric emission of long-duration gamma-ray bursts.
title The Photospheric Emission of a Short-Duration Gamma-Ray Burst Emerging from a Realistic Binary Neutron Star Merger
topic High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2509.12505