Marongiu, M, Guidorzi, C, Stratta, G, Gomboc, A, Jordana-Mitjans, N, Dichiara, S, Kobayashi, S, Kopac, D and Mundell, CG (2022) Radio data challenge the broadband modelling of GRB 160131A afterglow. Astronomy & Astrophysics, 658. ISSN 1432-0746

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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.

Item Type:	Article
Uncontrolled Keywords:	2-COMPONENT JET; Astronomy & Astrophysics; COMPTON EMISSION; data analysis; ENERGY INJECTION; gamma-ray burst; GAMMA-RAY-BURST; GRB160131A; individual; LIGHT CURVES; LINEAR-POLARIZATION; methods; non-thermal; Physical Sciences; PROMPT EMISSION; radiation mechanisms; RELATIVISTIC HYDRODYNAMICS; REVERSE SHOCK; Science & Technology; X-RAY; Science & Technology; Physical Sciences; Astronomy & Astrophysics; radiation mechanisms; non-thermal; gamma-ray burst; individual; GRB160131A; methods; data analysis; GAMMA-RAY-BURST; LIGHT CURVES; X-RAY; REVERSE SHOCK; RELATIVISTIC HYDRODYNAMICS; LINEAR-POLARIZATION; COMPTON EMISSION; ENERGY INJECTION; 2-COMPONENT JET; PROMPT EMISSION; 0201 Astronomical and Space Sciences; Astronomy & Astrophysics
Subjects:	Q Science > QB Astronomy
Divisions:	Astrophysics Research Institute
Publisher:	EDP Sciences
SWORD Depositor:	A Symplectic
Date Deposited:	08 Nov 2022 09:51
Last Modified:	08 Nov 2022 09:51
DOI or ID number:	10.1051/0004-6361/202140403
URI:	https://researchonline.ljmu.ac.uk/id/eprint/18059

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