Observational Evidence for a Correlation between Peak Luminosities and Beaming in Gamma-Ray Bursts
Abstract
We calculate the unseen-but-true gamma-ray burst (GRB) event rate from a current flux-limited sample of 33 GRBs with individually measured redshifts. We consider a GRB event rate that is proportional to the star formation rate, in view of the GRB-supernovae association in SN 1998bw and GRB 030329. By fitting a lognormal distribution of GRB peak luminosities, we find a ratio 1/fr~=450 for the true-to-observed GRB event rates. This provides an independent derivation of the GRB beaming factor 1/fb~=500 obtained by Frail et al. from sources with standard GRB energies. We discuss applications to GRB 980425.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 2003
- DOI:
- 10.1086/378146
- arXiv:
- arXiv:astro-ph/0307058
- Bibcode:
- 2003ApJ...593L..15V
- Keywords:
-
- Gamma Rays: Bursts;
- Astrophysics
- E-Print:
- to appear in ApJ Lett