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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127 Citations (Scopus)


We report polarization measurements in two prompt emissions of gamma-ray bursts, GRB110301A and GRB110721A, observed with the gamma-ray burst polarimeter (GAP) on borad the IKAROS solar sail mission. We detected linear polarization signals from each burst with polarization degree of Π = 70 ± 22% with statistical significance of 3.7σ for GRB110301A, and Π = 84 +16 - 28% with 3.3σ confidence level for GRB110721A. We did not detect any significant change of polarization angle. These two events had shorter durations and dimmer brightness compared with GRB100826A, which showed a significant change of polarization angle, as reported in Yonetoku etal. Synchrotron emission model can be consistent with the data of the three GRBs, while the photospheric quasi-thermal emission model is not favored. We suggest that magnetic field structures in the emission region are globally ordered fields advected from the central engine.

Original languageEnglish
Article numberL1
JournalAstrophysical Journal Letters
Issue number1
Publication statusPublished - 2012 Oct 10


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