A possible observational evidence for $θ^{-2}$ angular distribution of opening half-angle of GRB jets

Daisuke Yonetoku; Ryo Yamazaki; Takashi Nakamura; Toshio Murakami

doi:10.1111/j.1365-2966.2005.09398.x

paper

A possible observational evidence for $θ^{- 2}$ angular distribution of opening half-angle of GRB jets

arXiv:astro-ph/0503254 · doi:10.1111/j.1365-2966.2005.09398.x

Abstract

We propose a method to estimate the pseudo jet opening half-angle of GRBs using the spectral peak energy ($\Ep$)--peak luminosity relation (so called Yonetoku relation) as well as the $\Ep$--collimation-corrected $γ$ -ray energy relation (so called Ghirlanda relation). For bursts with known jet break times and redshifts, we compared the pseudo jet opening half-angle with the standard one and found that the differences are within a factor 2. We apply the method to 689 long GRBS. We found that the distribution function of the pseudo jet opening half-angle obeys $f (θ_{j}) \propto θ_{j}^{- 2.2 \pm 0.2}$ with possible cutoffs for $θ_{j} < 0.04$ and $θ_{j} > 0.3$ although the log-normal fit is also possible. $θ^{- 2}$ distribution is compatible with the structured jet model. From the distribution function we found that the beaming correction for the rate of GRBs is $\sim 340$ , which means $\sim 1 0^{- 5}$ yr $^{- 1}$ galaxy $^{- 1}$ or only one in $1 0^{2}$ type Ib/c supernovae. We also found the evolution of the distribution function as a function of the redshift.

5 pages, 5 figures, submitted to MNRAS

A possible observational evidence for $θ^{- 2}$ angular distribution of opening half-angle of GRB jets

Abstract

References in corpus (30)

Cited by in corpus (14)

A possible observational evidence for θ−2 angular distribution of opening half-angle of GRB jets

Abstract

References in corpus (30)

Cited by in corpus (14)

A possible observational evidence for $θ^{- 2}$ angular distribution of opening half-angle of GRB jets