Rotation of Polarization Angle in Gamma-Ray Burst Prompt Phase. III. The Influence of the Magnetic Field Orientation

Abstract

Polarization is very sensitive to the configuration of the magnetic field in the radiation region. In addition to polarization curve and polarization spectrum, studies of polarization angle (PA) rotation spectrum is also crucial. In this paper, we use a simple parametric magnetic reconnection model with a large-scale aligned magnetic field in the radiation region to study the effects of field orientation on the PA rotations. Under different field orientations, variations of the PA rotation with parameters and the PA rotation spectra are studied. We find that the conclusions obtained in our previous works are almost independent of the field orientations. The area of the parameter space with $\Delta$PA $>10^{\circ }$ will shrink as the value of field orientation ($\delta$) increases for $0^{\circ }<\delta <90^{\circ }$. The $\Delta$PA values would be the same for two complementary field orientations. For two particular magnetic field orientations ($\delta =0^{\circ }$ and $90^{\circ }$), the $\Delta$PA would also only be $0^{\circ }$ or $90^{\circ }$ within the burst duration.

9 pages, 2 figures, 1 table, ApJ accepted