Journal Article

PUBDB-2023-07261

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Temporal and Spectral Evolution of Gamma-Ray Burst Broad Pulses: Identification of High-latitude Emission in the Prompt Emission

Tak, D. (Corresponding author)DESY* ; Uhm, Z. L. ; Racusin, J. ; Zhang, B. ; Guiriec, S. ; Kocevski, D. ; Zhang, B.-B. ; McEnery, J.

2023
Institute of Physics Publ. London

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Please use a persistent id in citations: doi:10.3847/1538-4357/acc581  doi:10.3204/PUBDB-2023-07261

Report No.: arXiv:2212.07095

Abstract: We perform a detailed analysis of broad pulses in bright gamma-ray bursts (GRBs) to understand the evolution of GRB broad pulses. Using the temporal and spectral properties, we test the high-latitude emission (HLE) scenario in the decaying phase of broad pulses. The HLE originates from the curvature effect of a relativistic spherical jet, where higher-latitude photons are delayed and softer than the observer's line-of-sight emission. The signature of HLE has not yet been identified undisputedly during the prompt emission of GRBs. The HLE theory predicts a specific relation, $F_v$,${_E}_p$∝$E^{2}_{p}$, between the peak energy $E_p$ in $νF_ν$ spectra and the spectral flux $F_ν$ measured at $E_p$. . We search for evidence of this relation in 2157 GRBs detected by the Gamma-ray Burst Monitor on board the Fermi Gamma-ray Space Telescope from 2008 to 2017. After imposing unbiased selection criteria in order to minimize contamination in a signal by background and overlaps of pulses, we build a sample of 32 broad pulses in 32 GRBs. We perform a time-resolved spectral analysis on each of these 32 broad pulses and find that the evolution of 18 pulses (56%) is clearly consistent with the HLE relation. For the 18 broad pulses, the exponent δ in the relation of $F_v$,${_E}_p$∝$E^{\delta}_{p}$ is distributed as a Gaussian function with a median and width of 1.99 and 0.34, respectively. This result provides a constraint on the emission radius of GRBs with the HLE signature.

Note: 30 pages, 36 figures, accepted to ApJ

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Contributing Institute(s):

1. VERITAS (Z_VER)

Research Program(s):

1. 613 - Matter and Radiation from the Universe (POF4-613) (POF4-613)

Experiment(s):

1. Very Energetic Radiation Imaging Telescope Array System

Appears in the scientific report 2023

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