Beaming in gamma-ray bursts: evidence for a standard energy reservoir

Creators: Frail, D. A.; Kulkarni, S. R.; Sari, R.; Djorgovski, S. G.; Bloom, J. S.; Galama, T. J.; Reichart, D. E.; Berger, E.; Harrison, F. A.; Price, P. A.; Yost, S. A.; Diercks, A.; Goodrich, R. W.; Chaffee, F.

Abstract

We present a comprehensive sample of all gamma-ray burst (GRB) afterglows with known distances, and we derive their conical opening angles based on observed broadband breaks in their light curves. Within the framework of this conical jet model, we correct for the geometry and we find that the gamma-ray energy release is narrowly clustered around 5 × 10^(50) ergs. We draw three conclusions. First, the central engines of GRBs release energies that are comparable to ordinary supernovae. Second, the broad distribution in fluence and luminosity for GRBs is largely the result of a wide variation of opening angles. Third, only a small fraction of GRBs are visible to a given observer, and the true GRB rate is several hundred times larger than the observed rate.

Additional Information

© 2001 American Astronomical Society. Received 2001 July 6; accepted 2001 October 17; published 2001 November 1. Our research is supported by NASA and NSF. We thank various organizations for fellowships to J. S. B. (Fannie & John Hertz Foundation), A. D. (Millikan Fellow), T. J. G. (Fairchild Fellow), D. E. R. (Hubble Fellow), and R. S. (Fairchild Senior Fellow). The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. We thank the staff at the Keck and Palomar Observatories for their expert help during many observing runs. The W. M. Keck Observatory is operated by the California Association for Research in Astronomy, a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. It was made possible by the generous financial support of the W. M. Keck Foundation.

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