Abstract
Context. Gamma-ray burst (GRB) afterglows originate from the interaction between the relativistic ejecta and the surrounding medium. Consequently, their properties depend on several aspects: radiation mechanisms, relativistic shock micro-physics, circumburst environment, and the structure and geometry of the relativistic jet. While the standard afterglow model accounts for the overall spectral and temporal evolution for a number of GRBs, its validity limits emerge when the data set is particularly rich and constraining, especially in the radio band. Aims. We aimed to model the afterglow of the long GRB 160131A (redshift z = 0.972), for which we collected a rich, broadband, and accurate data set, spanning from 6 × 108 Hz to 7 × 1017 Hz in frequency, and from 330 s to 160 days post-burst in time. Methods. We modelled the spectral and temporal evolution of this GRB afterglow through two approaches: (1) the adoption of empirical functions to model an optical/X-ray data set, later assessing their compatibility with the radio domain; and (2) the inclusion of the entire multi-frequency data set simultaneously through the Python package named SAGA (Software for AfterGlow Analysis), to obtain an exhaustive and self-consistent description of the micro-physics, geometry, and dynamics of the afterglow. Results. From deep broadband analysis (from radio to X-ray frequencies) of the afterglow light curves, GRB 160131A outflow shows evidence of jetted emission. Moreover, we observe dust extinction in the optical spectra, and energy injection in the optical/X-ray data. Finally, radio spectra are characterised by several peaks that could be due to either interstellar scintillation (ISS) effects or a multi-component structure. Conclusions. The inclusion of radio data in the broadband set of GRB 160131A makes a self-consistent modelling barely attainable within the standard model of GRB afterglows.
| Original language | English |
|---|---|
| Article number | A11 |
| Number of pages | 32 |
| Journal | Astronomy and Astrophysics |
| Volume | 658 |
| Early online date | 27 Jan 2022 |
| DOIs | |
| Publication status | Published - 1 Feb 2022 |
Bibliographical note
Funding Information:Acknowledgements. We thank the anonymous referee for helping us improve the paper. Support for this work was provided by Università degli Studi di Ferrara through grant FIR 2018 “A Broad-band study of Cosmic Gamma-Ray Burst Prompt and Afterglow Emission” (PI Guidorzi). M. Marongiu acknowledges financial support from the Italian Ministry of University and Research – Project Proposal CIR01_00010, and the University of Ferrara for the financial support of his PhD scholarship (during the data analysis and the interpretation of the results). M. Marongiu is very grateful to R. Martone for useful conversations about GRB science; moreover, M. Marongiu thanks P. Bergamini and G. Angora for the useful discussion about Python programming language and data analysis. A. Gomboc acknowledges the financial support from the Slovenian Research Agency (grants P1-0031, I0-0033, J1-8136, J1-2460) and networking support by the COST Actions CA16104 GWverse and CA16214 PHAROS. N. Jordana and C.G. Mundell acknowledge financial support from Mr Jim Sherwin and Mrs Hiroko Sherwin. D. Kopac acknowledges the financial support from the Slovenian Research Agency (research core funding No. P1-0188). The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc..
Keywords
- Gamma-ray burst: individual: GRB160131A Methods: data analysis
- Radiation mechanisms: non-thermal
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science