Polarization of gamma-ray burst afterglows in the synchrotron self-Compton process from a highly relativistic jet
Linear polarization has been observed in both the prompt phase and afterglow of some bright gamma-ray bursts（GRBs）.Polarization in the prompt phase spans a wide range,and may be as high as 50%.In the afterglow phase,however,it is usually below 10%.According to the standard fireball model,GRBs are pr...
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| Published in | Chinese physics C Vol. 41; no. 4; pp. 108 - 116 |
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| Main Author | |
| Format | Journal Article |
| Language | English |
| Published |
01.04.2017
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| Online Access | Get full text |
| ISSN | 1674-1137 0254-3052 |
| DOI | 10.1088/1674-1137/41/4/045101 |
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| Summary: | Linear polarization has been observed in both the prompt phase and afterglow of some bright gamma-ray bursts（GRBs）.Polarization in the prompt phase spans a wide range,and may be as high as 50%.In the afterglow phase,however,it is usually below 10%.According to the standard fireball model,GRBs are produced by synchrotron radiation and Compton scattering process in a highly relativistic jet ejected from the central engine.It is widely accepted that prompt emissions occur in the internal shock when shells with different velocities collide with each other,and the magnetic field advected by the jet from the central engine can be ordered on a large scale.On the other hand,afterglows are often assumed to occur in the external shock when the jet collides with interstellar medium,and the magnetic field produced by the shock through,for example,Weibel instability,is possibly random.In this paper,we calculate the polarization properties of the synchrotron self-Compton process from a highly relativistic jet,in which the magnetic field is randomly distributed in the shock plane.We also consider the generalized situation where a uniform magnetic component perpendicular to the shock plane is superposed on the random magnetic component.We show that it is difficult for the polarization to be larger than 10% if the seed electrons are isotropic in the jet frame.This may account for the observed upper limit of polarization in the afterglow phase of GRBs.In addition,if the random and uniform magnetic components decay with time at different speeds,then the polarization angle may change 90° during the temporal evolution. |
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| Bibliography: | 11-5641/O4 Hal-Nan Lin1, Xin Li1,2,Zhe Chang3（ 1 Department of Physics, Chongqing University, Chongqing 401331, China ; 2 State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China ;3 Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China） gamma-ray burst, polarization, synchrotron radiation, Compton scattering Linear polarization has been observed in both the prompt phase and afterglow of some bright gamma-ray bursts（GRBs）.Polarization in the prompt phase spans a wide range,and may be as high as 50%.In the afterglow phase,however,it is usually below 10%.According to the standard fireball model,GRBs are produced by synchrotron radiation and Compton scattering process in a highly relativistic jet ejected from the central engine.It is widely accepted that prompt emissions occur in the internal shock when shells with different velocities collide with each other,and the magnetic field advected by the jet from the central engine can be ordered on a large scale.On the other hand,afterglows are often assumed to occur in the external shock when the jet collides with interstellar medium,and the magnetic field produced by the shock through,for example,Weibel instability,is possibly random.In this paper,we calculate the polarization properties of the synchrotron self-Compton process from a highly relativistic jet,in which the magnetic field is randomly distributed in the shock plane.We also consider the generalized situation where a uniform magnetic component perpendicular to the shock plane is superposed on the random magnetic component.We show that it is difficult for the polarization to be larger than 10% if the seed electrons are isotropic in the jet frame.This may account for the observed upper limit of polarization in the afterglow phase of GRBs.In addition,if the random and uniform magnetic components decay with time at different speeds,then the polarization angle may change 90° during the temporal evolution. |
| ISSN: | 1674-1137 0254-3052 |
| DOI: | 10.1088/1674-1137/41/4/045101 |