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arXiv · 1208.5287

Magnetic Structures in Gamma-Ray Burst Jets Probed by Gamma-Ray Polarization

Daisuke Yonetoku·Toshio Murakami·Shuichi Gunji·Tatehiro Mihara·Kenji Toma·Yoshiyuki Morihara·Takuya Takahashi·Yudai Wakashima·Hajime Yonemochi·Tomonori Sakashita·Noriyuki Toukairin·Hirofumi Fujimoto·Yoshiki Kodama
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Abstract

We report polarization measurements in two prompt emissions of gamma-ray bursts, GRB 110301A and GRB 110721A, observed with the Gamma-ray burst polarimeter (GAP) aboard IKAROS solar sail mission. We detected linear polarization signals from each burst with polarization degree of $Π= 70 \pm 22$% with statistical significance of $3.7 σ$ for GRB 110301A, and $Π= 84^{+16}_{-28}$% with $3.3 σ$ confidence level for GRB 110721A. We did not detect any significant change of polarization angle. These two events had shorter durations and dimmer brightness compared with GRB 100826A, which showed a significant change of polarization angle, as reported in Yonetoku et al. (2011). Synchrotron emission model can be consistent with all the data of the three GRBs, while photospheric quasi-thermal emission model is not favorable. We suggest that magnetic field structures in the emission region are globally-ordered fields advected from the central engine.

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Daisuke Yonetoku, Toshio Murakami, Shuichi Gunji, Tatehiro Mihara, Kenji Toma, Yoshiyuki Morihara, Takuya Takahashi, Yudai Wakashima, Hajime Yonemochi, Tomonori Sakashita, Noriyuki Toukairin, Hirofumi Fujimoto, Yoshiki Kodama. 2012-08-27. Magnetic Structures in Gamma-Ray Burst Jets Probed by Gamma-Ray Polarization. https://doi.org/10.1088/2041-8205%2F758%2F1%2Fl1

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