Possible observational evidence for the θ-2 angular distribution of the opening half-angle of gamma-ray burst jets

Yonetoku Daisuke

Yamazaki Ryo

Nakamura Takashi

Murakami Toshio

Monthly Notices of the Royal Astronomical Soceity

We propose a method to estimate the jet opening half-angle of gamma-ray bursts (GRBs) using the spectral peak energy (Ep)–peak luminosity relation (the so-called Yonetoku relation) as well as the Ep–collimation-corrected gamma-ray energy relation (the so-called Ghirlanda relation). For bursts with known jet break times and redshifts, we have compared the derived jet opening half-angle with that measured and found that the differences are within a factor of 2. We apply the method to 689 long GRBs. We have found that the distribution function of the derived jet opening half-angle obeys f(θj) θ-2.2±0.2j, although a lognormal fit is also possible. θ-2 distribution is compatible with the structured jet model. From the distribution function we have found that the beaming correction for the rate of GRBs is ~340, which means ~10-5 yr-1 galaxy-1 or only one in 102 Type Ib/c supernovae. We have also found the evolution of the distribution function as a function of the redshift.

gamma-rays: bursts

gamma-rays: observations

gamma-rays: theory

Astronomy. Space sciences [ 440 ]

eng

Blackwell

Copyright (c) 2005 Royal Astronomical Society

[ISSN] 0035-8711

[DOI] 10.1111/j.1365-2966.2005.09398.x

[DOI] http://dx.doi.org/10.1111/j.1365-2966.2005.09398.x isVersionOf