Statistical Properties of Gamma-Ray Burst Polarization

Authors

Kenji Toma, Pennsylvania State University - Main CampusFollow
Takanori Sakamoto, University of Maryland - Baltimore CountyFollow
Bing Zhang, University of Nevada, Las Vegas
Joanne E. Hill, Universities Space Research AssociationFollow
Mark L. McConnell, University of New Hampshire - Main CampusFollow
Peter F. Bloser, University of New HampshireFollow
Ryo Yamazaki, Hiroshima University
Kunihito Ioka, High Energy Accelerator Research OrganizationFollow
Takashi Nakamura, Kyoto University

Abstract

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 light-curve information currently collected. Polarization measurements will lead to unambiguous answers to several of these questions. Recent developments in X-ray and γ-ray polarimetry techniques have demonstrated a significant increase in sensitivity, enabling several new mission concepts, e.g., Polarimeters for Energetic Transients (POET), 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 small-scale 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 (N_m/N_d) and the distributions of the polarization degrees (Π) can be used as the criteria. If N_m/N_d > 30% and Π is clustered between 0.2 and 0.7, the SO model will be favored. If, instead, N_m/N_d < 15%, then the SR or CD model will be favored. If several events with Π>0.8 are observed, then the CD model will be favored.

Department

Space Science Center

Publication Date

5-27-2009

Journal Title

Astrophysical Journal

Publisher

American Astronomical Society

Digital Object Identifier (DOI)

10.1088/0004-637X/698/2/1042

Document Type

Article

Recommended Citation

Toma, Kenji; Sakamoto, Takanori; Zhang, Bing; Hill, Joanne E.; McConnell, Mark L.; Bloser, Peter F.; Yamazaki, Ryo; Ioka, Kunihito; and Nakamura, Takashi, "Statistical Properties of Gamma-Ray Burst Polarization" (2009). Astrophysical Journal. 4.
https://scholars.unh.edu/ssc/4

Rights

© 2009. The American Astronomical Society.