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Study of emission mechanism of GRBs probed by the gamma-ray polarization with IKAROS-GAP

Published online by Cambridge University Press:  05 September 2012

Daisuke Yonetoku ,
Toshio Murakami ,
Tomonori Sakashita ,
Yoshiyuki Morihara ,
Shuichi Gunji ,
Tatehiro Mihara  and
Kenji Toma
Daisuke Yonetoku
Affiliation:
College of Science and Engineering, School of Mathematics and Physics, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan, email: (DY) yonetoku@astro.s.kanazawa-u.ac.jp
Toshio Murakami
Affiliation:
College of Science and Engineering, School of Mathematics and Physics, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan, email: (DY) yonetoku@astro.s.kanazawa-u.ac.jp
Tomonori Sakashita
Affiliation:
College of Science and Engineering, School of Mathematics and Physics, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan, email: (DY) yonetoku@astro.s.kanazawa-u.ac.jp
Yoshiyuki Morihara
Affiliation:
College of Science and Engineering, School of Mathematics and Physics, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan, email: (DY) yonetoku@astro.s.kanazawa-u.ac.jp
Shuichi Gunji
Affiliation:
Department of Physics, Faculty of Science, Yamagata University, 1-4-12, Koshirakawa, Yamagata, Yamagata 990-8560, Japan
Tatehiro Mihara
Affiliation:
Cosmic Radiation Laboratory, RIKEN, 2-1, Hirosawa, Wako City, Saitama 351-0198, Japan
Kenji Toma
Affiliation:
Department of Earth and Space Science, Osaka University, Toyonaka 560-0043, Japan
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Abstract

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We report a polarization measurement in prompt γ-ray emission of GRB 100826A with the Gamma-Ray Burst Polarimeter (GAP) aboard the small solar power sail demonstrator IKAROS. We detected a firm change of polarization angle (PA) during the prompt emission with 99.9% (3.5 σ) confidence level, and an average polarization degree (Π) of 27 ± 11% with 99.4% (2.9 σ) confidence level. Here the quoted errors are given at 1 σ confidence level for two parameters of interest. Non-axisymmetric (e.g., patchy) structures of the magnetic fields and/or brightness inside the relativistic jet are therefore required within the observable angular scale of ~ Γ−1. Our observation strongly indicates that the polarization measurement is a powerful tool to constrain the GRB production mechanism, and more theoretical works are needed to discuss the data in more details.

Keywords

Gamma-Ray Burstspolarizationemission mechanism
Type
Poster Papers
Information
Proceedings of the International Astronomical Union , Volume 7 , Symposium S279: Death of Massive Stars: Supernovae and Gamma-Ray Bursts , April 2011 , pp. 425 - 426
Copyright
Copyright © International Astronomical Union 2012

References

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