A Comptonized Fireball Bubble Fits the Second Extragalactic Magnetar Giant Flare GRB 231115A
Abstract Magnetar giant flares (MGFs), originating from noncatastrophic magnetars, share noteworthy similarities with some short gamma-ray bursts (GRBs). However, understanding their detailed origin and radiation mechanisms remains challenging due to limited observations. The discovery of MGF GRB 23...
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Published in | Astrophysical journal. Letters Vol. 963; no. 1; p. L10 |
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Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
Austin
The American Astronomical Society
01.03.2024
IOP Publishing |
Subjects | |
Online Access | Get full text |
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Summary: | Abstract
Magnetar giant flares (MGFs), originating from noncatastrophic magnetars, share noteworthy similarities with some short gamma-ray bursts (GRBs). However, understanding their detailed origin and radiation mechanisms remains challenging due to limited observations. The discovery of MGF GRB 231115A, the second extragalactic MGF located in the Cigar galaxy at a luminosity distance of ∼3.5 Mpc, offers yet another significant opportunity for gaining insights into the aforementioned topics. This Letter explores its temporal properties and conducts a comprehensive analysis of both the time-integrated and time-resolved spectra through empirical and physical model fitting. Our results reveal certain properties of GRB 231115A that bear resemblances to GRB 200415A. We employ a Comptonized fireball bubble model, in which the Compton cloud, formed by the magnetar wind with high density
e
±
, undergoes Compton scattering and inverse Compton scattering, resulting in reshaped thermal spectra from the expanding fireball at the photosphere radius. This leads to dynamic shifts in dominant emission features over time. Our model successfully fits the observed data, providing a constrained physical picture, such as a trapped fireball with a radius of ∼1.95 × 10
5
cm and a high local magnetic field of 2.5 × 10
16
G. The derived peak energy and isotropic energy of the event further confirm the burst’s MGF origin and its contribution to the MGF-GRB sample. We also discuss prospects for further gravitational wave detection associated with MGFs, given their high-event-rate density (∼8 × 10
5
Gpc
−3
yr
−1
) and ultrahigh local magnetic field. |
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Bibliography: | AAS51811 High-Energy Phenomena and Fundamental Physics |
ISSN: | 2041-8205 2041-8213 |
DOI: | 10.3847/2041-8213/ad2839 |