Polarization of GRB prompt emission and its application to POLAR’s data

作     者：Mi-Xiang Lan Xue-Feng Wu Zi-Gao Dai Mi-Xiang Lan;Xue-Feng Wu;Zi-Gao Dai

作者机构：Center for Theoretical Physics and College of PhysicsJilin UniversityChangchun 130012China Purple Mountain ObservatoryChinese Academy of SciencesNanjing 210008China School of Astronomy and Space ScienceNanjing UniversityNanjing 210093China Key Laboratory of Modern Astronomy and Astrophysics(Nanjing University)Ministry of EducationNanjing 210093China 

出 版 物：《Research in Astronomy and Astrophysics》 (天文和天体物理学研究（英文版）)

年 卷 期：2021年第21卷第3期

页      面：43-56页

核心收录：

学科分类：0709[理学-地质学] 07[理学] 0708[理学-地球物理学] 070401[理学-天体物理] 0704[理学-天文学] 0825[工学-航空宇航科学与技术] 

基　　金：supported by the National Key Research and Development Program of China(Grant No.2017YFA0402600) the National Natural Science Foundation of China(NSFC)(Grant Nos.11573014,11673068,11725314,11833003 and 11903014) partially supported by the Key Research Program of Frontier Sciences(QYZDB-SSW-SYS005) the Strategic Priority Research Program“Multi-waveband gravitational wave Universe”(Grant No.XDB23040000)of the Chinese Academy of Sciences the“333 Project”of Jiangsu province supported by the Natural Science Foundation of Jiangsu Province(Grant No.BK 20171109) the Fundamental Research Funds for the Central Universities in part by NSFC(Grant No.11847310) the Seeds Funding of Jilin University。 

主　　题：gamma-ray burst:general magnetic fields polarization radiation mechanisms:nonthermal 

摘      要：Synchrotron emission polarization is very sensitive to the magnetic field configuration.Recently,polarization of synchrotron emission with a mixed(SM)magnetic field in the gamma-ray burst(GRB)afterglow phase has been developed.Here,we apply these SM models to the GRB prompt phase and compare their polarization properties with that of synchrotron emission in purely ordered(SO)magnetic field.We find that the polarization properties in an SM model are very similar to these in a corresponding SO model(e.g.,synchrotron emission in a mixed magnetic field with an aligned ordered part(SMA)and synchrotron emission with a purely ordered aligned magnetic field(SOA)),only with a lower polarization degree(PD).We also discuss the statistical properties of the models.We find PDs of the simulated bursts are concentrated around 25%for both SOA and synchrotron emission in a purely ordered toroidal magnetic field(SOT),while they can range from 0%to 25%for SMA and synchrotron emission in a mixed magnetic field with a toroidal ordered part(SMT),depending onξ_B value,i.e.,the ratio of magnetic reduction of the ordered magnetic field over that of random magnetic field.From statistics,if PDs of majority GRBs are non-zero,then it favors SO and SM models.Further,if there are some bright GRBs with prominently lower PDs than that of the majority GRBs,it favors SOT(SMT)models;if all the bright GRBs have comparable PDs with the majority ones,it favors SOA(SMA)models.Finally,we apply our results to POLAR’s data and find that~10%time-integrated PDs of the observed bursts favor SMA and SMT models,and theξ_B parameter of these bursts is constrained to be around 1.135.