Statistical properties of gamma-ray burst polarization

K. Toma, T. Sakamoto, B. Zhang, J. E. Hill, M. L. McConnell, P. E. Bloser, R. Yamazaki, K. Ioka, T. Nakamura

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The emission mechanism and the origin and structure of magnetic fields in gamma-ray burst (GRB) jets are among the most important open questions concerning the nature of the central engine of GRBs. In spite of extensive observational efforts, these questions remain to be answered and are difficult or even impossible to infer with the spectral and lightcurve information currently collected. Polarization measurements will lead to unambiguous answers to several of these questions. Recent developments in X-ray and y-ray polarimetry techniques have demonstrated a significant increase in sensitivity enabling several new mission concepts, e.g. POET (Polarimeters for Energetic Transients), providing wide field of view and broadband polarimetry measurements. If launched, missions of this kind would finally provide definitive measurements of GRB polarizations. We perform Monte Carlo simulations to derive the distribution of GRB polarizations in three emission models; the synchrotron model with a globally ordered magnetic field (SO model), the synchrotron model with a locally random magnetic field (SR model), and the Compton drag model (CD model). The results show that POET, or other polarimeters with similar capabilities, can constrain the GRB emission models by using the statistical properties of GRB polarizations. In particular, the ratio of the number of GRBs for which the polarization degrees can be measured to the number of GRBs that are detected (Nm/Nd) and the distributions of the polarization degrees (∏) can be used as the criteria. If N m/Nd > 30% and ∏ is clustered between 0.2 and 0.7, the SO model will be favored. If instead Nm/Nd < 15%, then the SR or CD model will be favored. If several events with ∏ > 0.8 are observed, then the CD model will be favored.

Original languageEnglish
Title of host publicationGamma-Ray Burst - 6th Huntsville Symposium
Number of pages3
Publication statusPublished - 2009
Externally publishedYes
Event6th Huntsville Symposium on Gamma-Ray Bursts - Huntsville, AL, United States
Duration: 2008 Oct 202008 Oct 23

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616


Conference6th Huntsville Symposium on Gamma-Ray Bursts
Country/TerritoryUnited States
CityHuntsville, AL


  • Polarization
  • Radiation mechanisms
  • γ-ray bursts
  • γ-ray sources

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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