2024ApJ...973....2L

In addition to the light curve and energy spectrum, polarization is also important for inferring the physical properties of the gamma-ray burst (GRB). Rotation of the polarization angle (PA) with time will cause depolarization of the time-integrated polarization degree. However, it has rarely been studied before. Here, we use a magnetic reconnection model with a large-scale ordered aligned magnetic field in the emitting region to study the influence of the parameters on the PA rotations in the GRB prompt phase. We find that the half-opening angle of the jet θ_j, the observational angle θ_V, and the bulk Lorentz factor Γ all have significant impacts on the PA rotations. The PA rotations are affected by the product value of θ_jΓ₀ (Γ₀ is the normalization factor of Γ with ${\rm{\Gamma }}{(r)={{\rm{\Gamma }}}_{0}(r/{r}_{0})}^{s}$), but are roughly independent of the concrete values of both θ_j and Γ₀. For the typical parameters, the changes of the PA within T₉₀ (△PA) would be within (12°, 66°) for slight off-axis observations, where T₉₀ is the duration of the burst with the accumulated flux density ranging from 5% to 95%. The q range for △PA > 10° becomes smaller with the increase of the product value of θ_jΓ₀. The most significant PA rotation with △PA ∼ 90° will happen when θ_jΓ₀ > 50 and 1.0 < q ≤ 1.2.