Afterglow polarizations in a stratified medium with effect of the equal arrival time surface
arXiv:2305.10590 · doi:10.3847/1538-4357/acd6ef
Abstract
The environment of gamma-ray burst (GRB) has an important influence on the evolution of jet dynamics and of its afterglow. Here we investigate the afterglow polarizations in a stratified medium with the equal arrival time surface (EATS) effect. Polarizations of multi-band afterglows are predicted. The effects of the parameters of the stratified medium on the afterglow polarizations are also investigated. We found the influences of the EATS effect on the afterglow polarizations become important for off-axis detections and PD bumps move to later times with the EATS effect. Even the magnetic field configurations, jet structure and observational angles are fixed, polarization properties of the jet emission could still evolve. Here, we assume a large-scale ordered magnetic field in the reverse-shock region and a two-dimensional random field in the forward-shock region. Then PD evolution is mainly determined by the evolution of parameter (the flux ratio between the reverse-shock region and forward-shock region) at early stage and by the evolution of the bulk Lorentz factor at late stage. Through the influences on the or , the observational energy band, observational angles, and the parameters of the stratified medium will finally affect the afterglow polarizations.
arXiv comment16 pages, 8 figures, accepted by ApJ
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