Multi-epoch afterglow rebrightenings in GRB 250129A: Evidence for successive shock interactions
Abstract
Most long gamma-ray bursts (GRBs) exhibit afterglows broadly consistent with external forward-shock emission, typically described by smooth broken power-law decays in the multiband light curve. However, a minority of well-sampled GRBs deviate from this behavior, including GRB 250129A. This object shows multiple late-time rebrightenings at X-ray and optical wavelengths. Rebrightenings are often attributed to energy injection from prolonged central engine activity, refreshed shocks from delayed shell collisions, density jumps in the ambient medium, or angular jet structure and viewing-angle effects. After analysing the prompt emission observed in gamma-rays and the near-infrared, we investigate the origin of X-ray and optical flaring episodes in GRB 250129A. Physical processes in the afterglow light curves were investigated using methods ranging from empirical fitting to Bayesian inference. The well-sampled flares and the connection between the prompt and afterglow emission allow us to test the consistency of the fireball model and alternative scenarios. Conducting the prompt and time-resolved analyses, we obtained an isotropic-equivalent energy of E_iso,gamma = (1.35 +/- 0.12) x 10^53 erg. By modeling the afterglow using an agnostic Bayesian framework (NMMA), we rule out both a single external-shock evolution and a one-time energy-injection scenario. Numerical calculations show that the rebrightening episodes are consistent with refreshed shocks from delayed collisions between relativistic shells. Based on the consistency between our analyses of the prompt and afterglow GRB 250129A data, we find that two statistically significant rebrightening episodes occur within 1.1 days post trigger and can be explained by a sequence of refreshed shocks. Temporally and spectrally rich GRB datasets such as the one presented in this work, provide a powerful means to test current modeling frameworks.
Cite
@article{arxiv.2603.08555,
title = {Multi-epoch afterglow rebrightenings in GRB 250129A: Evidence for successive shock interactions},
author = {D. Akl and S. Antier and H. Koehn and P. T. H. Pang and J. J. Geng and R. Gill and E. Abdikamalov and C. Adami and V. Aivazyan and L. Almeida and S. Alshamsi and C. Andrade and Q. André and C. Angulo-Valdez and J. -L. Atteia and K. Barkaoui and S. Basa and R. L. Becerra and P. Bendjoya and D. Berdikhan and E. Bernaud and S. Boissier and S. Brunier and A. Y. Burdanov and N. R. Butler and J. Chen and F. Colas and W. Corradi and M. W. Coughlin and D. Darson and T. Dietrich and D. Dornic and C. Douzet and C. Dubois and J. -G. Ducoin and T. du Laz and A. Durroux and D. Dutton and P. -A. Duverne and F. Dux and E. G. Elhosseiny and A. Esamdin and A. V. Filippenko and F. Fortin and M. Freeberg and L. García-García and M. Gillon and N. Globus and P. Gokuldass and N. Guessoum and P. Hello and R. Hellot and Y. H. M. Hendy and Y. L. Hua and T. Hussenot-Desenonges and R. Inasaridze and A. Iskandar and M. Jelínek and S. Karpov and A. Klotz and N. Kochiashvili and T. Laskar and A. Le Calloch and W. H. Lee and S. Leonini and X. Y. Li and A. Lien and C. Limonta and J. Liu and D. López-Cámara and F. Magnani and J. Mao and M. Mašek and E. Moreno Méndez and L. C. Menegazzi and W. Mercier and B. M. Mihov and M. Molham and S. Oates and M. Odeh and H. Peng and M. Pereyra and M. Pillas and T. Pradier and N. A. Rakotondrainibe and D. Reichart and J. -P. Rivet and F. D. Romanov and F. Sánchez-Álvarez and N. Sasaki and D. Schlekat and B. Schneider and A. Simon and L. Slavcheva-Mihova and R. Strausbaugh and T. R. Sun and A. Takey and M. Tanasan and D. Turpin and A. de Ugarte Postigo and L. T. Wang and X. F. Wang and Z. M. Wang and A. M. Watson and J. de Wit and Y. S. Yan and W. Zheng and S. Zúñiga-Fernández},
journal= {arXiv preprint arXiv:2603.08555},
year = {2026}
}