2024MNRAS.534.2516D

GRB 190829A has been widely studied due to its nature and the high-energy emission presented. Due to the detection of a very high energy component by the High Energy Stereoscopic System and the event's atypically middling luminosity, it has been categorized in a select, limited group of bursts bordering classic gamma-ray bursts (GRBs) and nearby sub-energetic events. Given the range of models utilized to adequately characterize the afterglow of this burst, it has proven challenging to identify the most probable explanation. Nevertheless, the detection of polarization data provided by the MASTER (Mobile Astronomical System of TElescope Robots) collaboration has added a new aspect to GRB 190829A that permits us to attempt to explore this degeneracy. In this paper, we present a polarization model coupled with a thin-shell synchrotron forward-shock model - a component in all models used to describe GRB 190829A's afterglow - in order to fit the polarization's temporal evolution with the existing upper limits ($\Pi < 6{{\ \rm per\, cent}}$). We find that the polarization generated from an on-axis emission is favoured for strongly anisotropic magnetic field ratios, while an off-axis scenario cannot be fully ruled out when a more isotropic framework is taken into account.