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

Daisuke Yonetoku, Toshio Murakami, Tomonori Sakashita, Yoshiyuki Morihara, Shuichi Gunji, Tatehiro Mihara, Kenji Toma

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


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 (II) 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 ∼ σ -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.

Original languageEnglish
Title of host publicationDeath of Massive Stars
Subtitle of host publicationSupernovae and Gamma-Ray Bursts
EditorsPeter W. A. San Antonio, Nobuyuki Kawai, Elena Pian
Number of pages2
Publication statusPublished - 2011 Apr

Publication series

NameProceedings of the International Astronomical Union
ISSN (Print)1743-9213
ISSN (Electronic)1743-9221


  • emission mechanism
  • Gamma-Ray Bursts
  • polarization


Dive into the research topics of 'Study of emission mechanism of GRBs probed by the gamma-ray polarization with IKAROS-GAP'. Together they form a unique fingerprint.

Cite this