The radio flare and multi-wavelength afterglow of the short GRB 231117A: energy injection from a violent shell collision

We present the early radio detection and multi-wavelength modeling of the short gamma-ray burst (GRB) 231117A at redshift $z=0.257$. The Australia Telescope Compact Array automatically triggered a 9-hour observation of GRB 231117A at 5.5 and 9 GHz following its detection by the Neil Gehrels Swift Observatory just 1.3 hours post-burst. Splitting this observation into 1-hour time bins, the early radio afterglow exhibited flaring, scintillating and plateau phases. The scintillation allowed us to place the earliest upper limit ($<10$ hours) on the size of a GRB blast wave to date, constraining it to $<1\times10^{16}$ cm. Multi-wavelength modeling of the full afterglow required a period of significant energy injection between $\sim 0.02$ and $1$ day. The energy injection was modeled as a violent collision of two shells: a reverse shock passing through the injection shell explains the early radio plateau, while an X-ray flare is consistent with a shock passing through the leading impulsive shell. Beyond 1 day, the blast wave evolves as a classic decelerating forward shock with an electron distribution index of $p=1.66\pm0.01$. Our model also indicates a jet-break at $\sim2$ days, and a half-opening angle of $θ_j=16\mathring{.}6 \pm 1\mathring{.}1$. Following the period of injection, the total energy is $ζ\sim18$ times the initial impulsive energy, with a final collimation-corrected energy of $E_{\mathrm{Kf}}\sim5.7\times10^{49}$ erg. The minimum Lorentz factors this model requires are consistent with constraints from the early radio measurements of $Γ>35$ to $Γ>5$ between $\sim0.1$ and $1$ day. These results demonstrate the importance of rapid and sensitive radio follow-up of GRBs for exploring their central engines and outflow behaviour.

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ArXiv.org
Published
2025-08-20
Citations
1
Primary Topic
Gamma-ray bursts and supernovae
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article
Field-Weighted Citation Impact
1.15

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article

The radio flare and multi-wavelength afterglow of the short GRB 231117A: energy injection from a violent shell collision

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1 citations
ArXiv.org
Gamma-ray bursts and supernovae
1.15
article

The radio flare and multi-wavelength afterglow of the short GRB 231117A: energy injection from a violent shell collision

B. Schneider, J. P. Anderson, E. A. Magnier, J. F. Agüí Fernández, F. Schüßler, N. R. Tanvir, D. H. Hartmann, A. Andersson, S. Schulze, Thomas de Boer, M. Gromadzki, G. E. Anderson, G. Pugliese, M. Fulton, B. Sbarufatti, Rob Fender, L. Rhodes, A. de Ugarte Postigo, Chien-Cheng Lin, K. P. Mooley, J. H. Gillanders, A. Martín-Carrillo, M. E. Bell, Danny T. H. Steeghs, S. D. Ryder, S. Yang, K. Ackley, Tayyaba Zafar, James K. Leung, Benjamin P. Gompertz, D. Malesani, D. R. Williams, M. E. Huber, V. D’Elia, M. Ferro, A. J. van der Horst, M. De Pasquale, Gavin P. Lamb, R. A. M. J. Wijers, Peter Hancock, S. R. Oates, A. J. Levan, K. C. Chambers, A. Rowlinson, N. P. M. Kuin, Z. X. Wang, David A. Green, Tista Mukherjee, H. M. Fausey, Hua Gao, R. J. Wainscoat, Eric Burns, R. Brivio, E. Ros, Shubham Srivastav, Amitabh Gulati, I. Worssam, T. W. Chen, Dimple Dimple, C. C. Thoene, R. Starling, S. D. Vergani, P O’Brien, Michael Nicholl, K. W. Smith, S. J. Smartt, P. Mínguez
article en
1 citations

Abstract

We present the early radio detection and multi-wavelength modeling of the short gamma-ray burst (GRB) 231117A at redshift $z=0.257$. The Australia Telescope Compact Array automatically triggered a 9-hour observation of GRB 231117A at 5.5 and 9 GHz following its detection by the Neil Gehrels Swift Observatory just 1.3 hours post-burst. Splitting this observation into 1-hour time bins, the early radio afterglow exhibited flaring, scintillating and plateau phases. The scintillation allowed us to place the earliest upper limit ($<10$ hours) on the size of a GRB blast wave to date, constraining it to $<1\times10^{16}$ cm. Multi-wavelength modeling of the full afterglow required a period of significant energy injection between $\sim 0.02$ and $1$ day. The energy injection was modeled as a violent collision of two shells: a reverse shock passing through the injection shell explains the early radio plateau, while an X-ray flare is consistent with a shock passing through the leading impulsive shell. Beyond 1 day, the blast wave evolves as a classic decelerating forward shock with an electron distribution index of $p=1.66\pm0.01$. Our model also indicates a jet-break at $\sim2$ days, and a half-opening angle of $θ_j=16\mathring{.}6 \pm 1\mathring{.}1$. Following the period of injection, the total energy is $ζ\sim18$ times the initial impulsive energy, with a final collimation-corrected energy of $E_{\mathrm{Kf}}\sim5.7\times10^{49}$ erg. The minimum Lorentz factors this model requires are consistent with constraints from the early radio measurements of $Γ>35$ to $Γ>5$ between $\sim0.1$ and $1$ day. These results demonstrate the importance of rapid and sensitive radio follow-up of GRBs for exploring their central engines and outflow behaviour.

ArXiv.org
Astronomy Australia Limited, UK Research and Innovation, Breakthrough Prize Foundation, Australian Government, Leverhulme Trust, European Commission, Commonwealth Scientific and Industrial Research Organisation, National Research Foundation, Danmarks Grundforskningsfond, Curtin University of Technology, National Natural Science Foundation of China, Canada Excellence Research Chairs, Government of Canada, Ministry of Education, India, Agencia Nacional de Investigación y Desarrollo, National Science and Technology Council, Max-Planck-Institut für Astronomie, Science and Technology Facilities Council
Openalex Percentile: Top 16%
Gamma-ray bursts and supernovae
1.15
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