The Radio Flare and Multiwavelength Afterglow of the Short GRB 231117A : Energy Injection from a Violent Shell Collision

Anderson, G. E. and Lamb, G. P. and Gompertz, B. P. and Rhodes, L. and Martin-Carrillo, A. and van der Horst, A. J. and Rowlinson, A. and Bell, M. E. and Chen, T.-W. and Fausey, H. M. and Ferro, M. and Hancock, P. J. and Oates, S. R. and Schulze, S. and Starling, R. L. C. and Yang, S. and Ackley, K. and Anderson, J. P. and Andersson, A. and Fernández, J. F. Agüí and Brivio, R. and Burns, E. and Chambers, K. C. and de Boer, T. and D’Elia, V. and De Pasquale, M. and de Ugarte Postigo, A. and Dimple and Fender, R. and Fulton, M. D. and Gao, H. and Gillanders, J. H. and Green, D. A. and Gromadzki, M. and Gulati, A. and Hartmann, D. H. and Huber, M. E. and Klingler, N. J. and Kuin, N. P. M. and Leung, J. K. and Levan, A. J. and Lin, C.-C. and Magnier, E. and Malesani, D. B. and Minguez, P. and Mooley, K. P. and Mukherjee, T. and Nicholl, M. and O’Brien, P. T. and Pugliese, G. and Rossi, A. and Ryder, S. D. and Sbarufatti, B. and Schneider, B. and Schüssler, F. and Smartt, S. J. and Smith, K. W. and Srivastav, S. and Steeghs, D. and Tanvir, N. R. and Thoene, C. C. and Vergani, S. D. and Wainscoat, R. J. and Wang, Z.-N. and Wijers, R. A. M. J. and Williams-Baldwin, D. and Worssam, I. and Zafar, T. (2025) The Radio Flare and Multiwavelength Afterglow of the Short GRB 231117A : Energy Injection from a Violent Shell Collision. The Astrophysical Journal, 994 (1). ISSN 0004-637X

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Abstract

We present the early radio detection and multiwavelength modeling of the short gamma-ray burst (GRB) 231117A at redshift z = 0.257. The Australia Telescope Compact Array automatically triggered a 9 hr observation of GRB 231117A at 5.5 and 9 GHz following its detection by the Neil Gehrels Swift Observatory just 1.3 hr post-burst. Splitting this observation into 1 hr time bins, the early radio afterglow exhibited flaring, scintillating and plateau phases. The scintillation allowed us to place the earliest upper limit ( 35 to Γ > 5 between ∼0.1 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.