Polarization Predictions in the GRB Prompt Phase with the Internal Shock Model

Abstract

As the standard gamma-ray burst (GRB) prompt-emission model, the internal shock (IS) model can reproduce the fast-rise and slow-decay features of the pulses in the GRB light curve. The time- and energy-dependent polarization can deliver important physical information on the emission region and can be used to test models. Polarization predictions for the GRB prompt phase with the magnetized IS model should be investigated carefully. The magnetic field of the magnetized IS model is very likely to be mixed and decays with radius. The synchrotron emission in the presence of such a decaying magnetic field can recover the Band-like spectrum of the GRB prompt phase. We investigate the dependence of the polarization of GRB prompt emission on both time and energy in the framework of the magnetized IS model. Due to the large range of parameters, it is hard to distinguish the magnetized IS model and the magnetic-reconnection model through polarization degree (PD) curves. The energy-dependent PD could increase toward the high-energy band for the magnetized IS model, while it decreases to zero above the megaelectronvolt band for the dissipative photosphere model. Therefore, we conclude that the energy dependence of PD can be used to distinguish these two models for the GRB prompt emission. Finally, we find that, independent of the observational energy band, the profiles of the ${\xi }_B-PD$ curve for the time-integrated and time-resolved PDs are very similar, where ${\xi }_B$ is the magnetic field strength ratio of the ordered component to the random component.

7 pages, 3 figures, accepted by ApJ

References in corpus (5)

• The Internal-Collision-Induced Magnetic Reconnection and Turbulence (ICMART) Model of Gamma-Ray Bursts
• Detailed polarization measurements of the prompt emission of five Gamma-Ray Bursts
• The POLAR Gamma-Ray Burst Polarization Catalog
• Gamma-ray burst internal shocks with magnetization
• The Synchrotron Polarization in Decaying Magnetic Field in Gamma-Ray Bursts

Cited by in corpus (7)

• Rotation of polarization angle in gamma-ray burst prompt phase
• Interpreting time-integrated polarization data of gamma-ray burst prompt emission
• The polarization-angle flip in GRB prompt emission
• Afterglow polarizations in a stratified medium with effect of the equal arrival time surface
• Time-averaging Polarimetric and Spectral Properties of Gamma-Ray Bursts
• Is gamma-ray burst polarization from photosphere emission?
• Time-integrated polarizations in GRB prompt phase via the Multi-window interpretation