GRB 230204B: GIT Discovery of a Fast Fading Afterglow Associated with an Energetic Gamma-Ray Burst from a Massive Star Progenitor

Vishwajeet Swain; Varun Bhalerao; Harsh Kumar; Mehul Goyal; Ankur Ghosh; Utkarsh Pathak; Poonam Chandra; Tomás Ahumada; G. C. Anupama; S. Bala; Sudhanshu Barway; Joshua S. Bloom; Dimple Dimple; Viraj Karambelkar; Mansi Kasliwal; Kuntal Misra; Josiah Purdum; Divita Saraogi; Jesper Sollerman; Aswin Suresh; Stéfan van der Walt; Gaurav Waratkar

doi:10.3847/1538-4357/ae459f

GRB 230204B: GIT Discovery of a Fast Fading Afterglow Associated with an Energetic Gamma-Ray Burst from a Massive Star Progenitor

Vishwajeet Swain^*
, Varun Bhalerao
, Harsh Kumar
, Mehul Goyal
, Ankur Ghosh
, Utkarsh Pathak
, Poonam Chandra
, Tomás Ahumada
, G. C. Anupama
, S. Bala
, Sudhanshu Barway
, Joshua S. Bloom
, Dimple
, Viraj Karambelkar
, Mansi Kasliwal
, Kuntal Misra
, Josiah Purdum
, Divita Saraogi
, Jesper Sollerman
, Aswin Suresh

Stéfan van der Walt, Gaurav Waratkar

^*Corresponding author for this work

Physics and Astronomy

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

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Abstract

We present a comprehensive multiwavelength study of a bright gamma-ray burst GRB 230204B, analyzing both prompt and afterglow emissions. This GRB is highly energetic, with an isotropic equivalent energy emission of E_iso ∼ 2.2 × 10⁵⁴ erg released during the prompt emission. The GROWTH-India Telescope discovered a bright afterglow (m_r = 15.55) that fades rapidly (∝t^−1.82). The prompt emission shows a strong thermal photospheric emission along with a nonthermal high-energy component. We explore the evolution of these components and find them to be consistent with the theoretical expectations of the fireball model. Afterglow modeling reveals an energetic jet (E_γ ≳ 10⁵² erg) expanding into a wind-type medium viewed nearly on-axis, suggesting a massive star progenitor with strong winds. We also explore correlations between the prompt emission and afterglow that may help to place GRB 230204B within the broader context of the long GRB population.

Original language	English
Article number	58
Number of pages	18
Journal	The Astrophysical Journal
Volume	1000
Issue number	1
Early online date	12 Mar 2026
DOIs	https://doi.org/10.3847/1538-4357/ae459f
Publication status	Published - 20 Mar 2026

Keywords

Wolf-Rayet stars
Relativistic jets
Gamma-ray bursts

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Swain, V., Bhalerao, V., Kumar, H., Goyal, M., Ghosh, A., Pathak, U., Chandra, P., Ahumada, T., Anupama, G. C., Bala, S., Barway, S., Bloom, J. S., Dimple, Karambelkar, V., Kasliwal, M., Misra, K., Purdum, J., Saraogi, D., Sollerman, J., ... Waratkar, G. (2026). GRB 230204B: GIT Discovery of a Fast Fading Afterglow Associated with an Energetic Gamma-Ray Burst from a Massive Star Progenitor. The Astrophysical Journal, 1000(1), Article 58. https://doi.org/10.3847/1538-4357/ae459f

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title = "GRB 230204B: GIT Discovery of a Fast Fading Afterglow Associated with an Energetic Gamma-Ray Burst from a Massive Star Progenitor",

abstract = "We present a comprehensive multiwavelength study of a bright gamma-ray burst GRB 230204B, analyzing both prompt and afterglow emissions. This GRB is highly energetic, with an isotropic equivalent energy emission of Eiso ∼ 2.2 × 1054 erg released during the prompt emission. The GROWTH-India Telescope discovered a bright afterglow (mr = 15.55) that fades rapidly (∝t−1.82). The prompt emission shows a strong thermal photospheric emission along with a nonthermal high-energy component. We explore the evolution of these components and find them to be consistent with the theoretical expectations of the fireball model. Afterglow modeling reveals an energetic jet (Eγ ≳ 1052 erg) expanding into a wind-type medium viewed nearly on-axis, suggesting a massive star progenitor with strong winds. We also explore correlations between the prompt emission and afterglow that may help to place GRB 230204B within the broader context of the long GRB population.",

keywords = "Wolf-Rayet stars, Relativistic jets, Gamma-ray bursts",

author = "Vishwajeet Swain and Varun Bhalerao and Harsh Kumar and Mehul Goyal and Ankur Ghosh and Utkarsh Pathak and Poonam Chandra and Tom{\'a}s Ahumada and Anupama, \{G. C.\} and S. Bala and Sudhanshu Barway and Bloom, \{Joshua S.\} and Dimple and Viraj Karambelkar and Mansi Kasliwal and Kuntal Misra and Josiah Purdum and Divita Saraogi and Jesper Sollerman and Aswin Suresh and \{van der Walt\}, St{\'e}fan and Gaurav Waratkar",

year = "2026",

month = mar,

day = "20",

doi = "10.3847/1538-4357/ae459f",

language = "English",

volume = "1000",

journal = "The Astrophysical Journal",

issn = "0004-637X",

publisher = "Institute of Physics Publishing Ltd",

number = "1",

}

Swain, V, Bhalerao, V, Kumar, H, Goyal, M, Ghosh, A, Pathak, U, Chandra, P, Ahumada, T, Anupama, GC, Bala, S, Barway, S, Bloom, JS, Dimple, Karambelkar, V, Kasliwal, M, Misra, K, Purdum, J, Saraogi, D, Sollerman, J, Suresh, A, van der Walt, S & Waratkar, G 2026, 'GRB 230204B: GIT Discovery of a Fast Fading Afterglow Associated with an Energetic Gamma-Ray Burst from a Massive Star Progenitor', The Astrophysical Journal, vol. 1000, no. 1, 58. https://doi.org/10.3847/1538-4357/ae459f

TY - JOUR

T1 - GRB 230204B

T2 - GIT Discovery of a Fast Fading Afterglow Associated with an Energetic Gamma-Ray Burst from a Massive Star Progenitor

AU - Swain, Vishwajeet

AU - Bhalerao, Varun

AU - Kumar, Harsh

AU - Goyal, Mehul

AU - Ghosh, Ankur

AU - Pathak, Utkarsh

AU - Chandra, Poonam

AU - Ahumada, Tomás

AU - Anupama, G. C.

AU - Bala, S.

AU - Barway, Sudhanshu

AU - Bloom, Joshua S.

AU - Dimple, null

AU - Karambelkar, Viraj

AU - Kasliwal, Mansi

AU - Misra, Kuntal

AU - Purdum, Josiah

AU - Saraogi, Divita

AU - Sollerman, Jesper

AU - Suresh, Aswin

AU - van der Walt, Stéfan

AU - Waratkar, Gaurav

PY - 2026/3/20

Y1 - 2026/3/20

N2 - We present a comprehensive multiwavelength study of a bright gamma-ray burst GRB 230204B, analyzing both prompt and afterglow emissions. This GRB is highly energetic, with an isotropic equivalent energy emission of Eiso ∼ 2.2 × 1054 erg released during the prompt emission. The GROWTH-India Telescope discovered a bright afterglow (mr = 15.55) that fades rapidly (∝t−1.82). The prompt emission shows a strong thermal photospheric emission along with a nonthermal high-energy component. We explore the evolution of these components and find them to be consistent with the theoretical expectations of the fireball model. Afterglow modeling reveals an energetic jet (Eγ ≳ 1052 erg) expanding into a wind-type medium viewed nearly on-axis, suggesting a massive star progenitor with strong winds. We also explore correlations between the prompt emission and afterglow that may help to place GRB 230204B within the broader context of the long GRB population.

AB - We present a comprehensive multiwavelength study of a bright gamma-ray burst GRB 230204B, analyzing both prompt and afterglow emissions. This GRB is highly energetic, with an isotropic equivalent energy emission of Eiso ∼ 2.2 × 1054 erg released during the prompt emission. The GROWTH-India Telescope discovered a bright afterglow (mr = 15.55) that fades rapidly (∝t−1.82). The prompt emission shows a strong thermal photospheric emission along with a nonthermal high-energy component. We explore the evolution of these components and find them to be consistent with the theoretical expectations of the fireball model. Afterglow modeling reveals an energetic jet (Eγ ≳ 1052 erg) expanding into a wind-type medium viewed nearly on-axis, suggesting a massive star progenitor with strong winds. We also explore correlations between the prompt emission and afterglow that may help to place GRB 230204B within the broader context of the long GRB population.

KW - Wolf-Rayet stars

KW - Relativistic jets

KW - Gamma-ray bursts

U2 - 10.3847/1538-4357/ae459f

DO - 10.3847/1538-4357/ae459f

M3 - Article

SN - 0004-637X

VL - 1000

JO - The Astrophysical Journal

JF - The Astrophysical Journal

IS - 1

M1 - 58

ER -

GRB 230204B: GIT Discovery of a Fast Fading Afterglow Associated with an Energetic Gamma-Ray Burst from a Massive Star Progenitor

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Keywords

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