Jet Structure Imprint on the Curvature Tail of Gamma-Ray Burst Prompt Emission

Zhen Yu Yan; Xiao Hong Zhao; Hendrik J. van Eerten; Jun Yang; Jiang Chuan Tuo; Shu Xu Yi; Chen Wei Wang; Wen Jun Tan; Shao Lin Xiong; Bin Bin Zhang

doi:10.3847/1538-4357/ae6f02

Jet Structure Imprint on the Curvature Tail of Gamma-Ray Burst Prompt Emission

Zhen Yu Yan
, Xiao Hong Zhao
, Hendrik J. van Eerten
, Jun Yang
, Jiang Chuan Tuo
, Shu Xu Yi
, Chen Wei Wang
, Wen Jun Tan
, Shao Lin Xiong
, Bin Bin Zhang

Nanjing University
Yunnan Observatories
Chinese Academy of Sciences
Zhengzhou University
Institute of High Energy Physics Chinese Academy of Science
University of the Chinese Academy of Sciences
Key Laboratory of Modern Astronomy and Astrophysics

Research output: Contribution to journal › Article › peer-review

Abstract

Even though the prompt emission of gamma-ray bursts (GRBs) is highly beamed, high-latitude emission still produces a distinct light-curve break after the intrinsic emission ceases and the edge of the jet comes into view. This curvature effect offers a direct probe of the jet structure during the prompt phase. To uncover the geometric structure of the GRB jet encoded in the prompt light-curve evolution, we develop a numerical model that calculates synchrotron light curves from structured jets to interpret the observed break. We apply this model to the prompt emission of GRB 230307A, which displays a rare late-time break. Our analysis demonstrates that simple spherical outflow and top-hat jet models are inadequate to reproduce the light curve. Instead, the observations are best described by a power-law wing jet with a uniform core ( (Formula presented) θcore=0.0147 rad) and a surrounding power-law wing. Our results demonstrate that the break in late-time prompt emission can be a powerful diagnostic of GRB jet structure.

Original language	English
Article number	75
Journal	Astrophysical Journal
Volume	1004
Issue number	1
Early online date	5 Jun 2026
DOIs	https://doi.org/10.3847/1538-4357/ae6f02
Publication status	Published - 10 Jun 2026

Funding

We are grateful to the referee for helpful comments. We thank Yi-Han Iris Yin, Rudra D. Patel, and Yue Wu for helpful comments. We acknowledge the support by the National Natural Science Foundation of China (grants 12573046 and 12121003 to B.-B.Z. and grants 12393811 and 12473048 to X.-H.Z.) and the science research grants from the China Manned Space Project (grant CMS-CSST-2021-B11 to B.-B.Z.). B.-B.Z. acknowledges support by the Fundamental Research Funds for the Central Universities and the Programme for Innovative Talents and Entrepreneurs in Jiangsu. B.-B.Z. and H.v.E. acknowledge support by Royal Society International Exchanges Cost Share 2022 NSFC award IEC\NSFC\223149. Z.-Y.Y. acknowledges support by the China Scholarship Council (202406190271) and the University of Bath Visiting Postgraduate Scholar program (249552753). Z.-Y.Y. is also supported by the Program for Outstanding PhD Candidates of Nanjing University (2025A06).

Keywords

Gamma-ray bursts (629)

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.3847/1538-4357/ae6f02Licence: CC BY

Cite this

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title = "Jet Structure Imprint on the Curvature Tail of Gamma-Ray Burst Prompt Emission",

abstract = "Even though the prompt emission of gamma-ray bursts (GRBs) is highly beamed, high-latitude emission still produces a distinct light-curve break after the intrinsic emission ceases and the edge of the jet comes into view. This curvature effect offers a direct probe of the jet structure during the prompt phase. To uncover the geometric structure of the GRB jet encoded in the prompt light-curve evolution, we develop a numerical model that calculates synchrotron light curves from structured jets to interpret the observed break. We apply this model to the prompt emission of GRB 230307A, which displays a rare late-time break. Our analysis demonstrates that simple spherical outflow and top-hat jet models are inadequate to reproduce the light curve. Instead, the observations are best described by a power-law wing jet with a uniform core ( (Formula presented) θcore=0.0147 rad) and a surrounding power-law wing. Our results demonstrate that the break in late-time prompt emission can be a powerful diagnostic of GRB jet structure.",

keywords = "Gamma-ray bursts (629)",

author = "Yan, \{Zhen Yu\} and Zhao, \{Xiao Hong\} and \{van Eerten\}, \{Hendrik J.\} and Jun Yang and Tuo, \{Jiang Chuan\} and Yi, \{Shu Xu\} and Wang, \{Chen Wei\} and Tan, \{Wen Jun\} and Xiong, \{Shao Lin\} and Zhang, \{Bin Bin\}",

year = "2026",

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doi = "10.3847/1538-4357/ae6f02",

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AU - Yan, Zhen Yu

AU - Zhao, Xiao Hong

AU - van Eerten, Hendrik J.

AU - Yang, Jun

AU - Tuo, Jiang Chuan

AU - Yi, Shu Xu

AU - Wang, Chen Wei

AU - Tan, Wen Jun

AU - Xiong, Shao Lin

AU - Zhang, Bin Bin

PY - 2026/6/10

Y1 - 2026/6/10

N2 - Even though the prompt emission of gamma-ray bursts (GRBs) is highly beamed, high-latitude emission still produces a distinct light-curve break after the intrinsic emission ceases and the edge of the jet comes into view. This curvature effect offers a direct probe of the jet structure during the prompt phase. To uncover the geometric structure of the GRB jet encoded in the prompt light-curve evolution, we develop a numerical model that calculates synchrotron light curves from structured jets to interpret the observed break. We apply this model to the prompt emission of GRB 230307A, which displays a rare late-time break. Our analysis demonstrates that simple spherical outflow and top-hat jet models are inadequate to reproduce the light curve. Instead, the observations are best described by a power-law wing jet with a uniform core ( (Formula presented) θcore=0.0147 rad) and a surrounding power-law wing. Our results demonstrate that the break in late-time prompt emission can be a powerful diagnostic of GRB jet structure.

AB - Even though the prompt emission of gamma-ray bursts (GRBs) is highly beamed, high-latitude emission still produces a distinct light-curve break after the intrinsic emission ceases and the edge of the jet comes into view. This curvature effect offers a direct probe of the jet structure during the prompt phase. To uncover the geometric structure of the GRB jet encoded in the prompt light-curve evolution, we develop a numerical model that calculates synchrotron light curves from structured jets to interpret the observed break. We apply this model to the prompt emission of GRB 230307A, which displays a rare late-time break. Our analysis demonstrates that simple spherical outflow and top-hat jet models are inadequate to reproduce the light curve. Instead, the observations are best described by a power-law wing jet with a uniform core ( (Formula presented) θcore=0.0147 rad) and a surrounding power-law wing. Our results demonstrate that the break in late-time prompt emission can be a powerful diagnostic of GRB jet structure.

KW - Gamma-ray bursts (629)

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Jet Structure Imprint on the Curvature Tail of Gamma-Ray Burst Prompt Emission

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Keywords

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