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Gamma-ray Burst Energetics an the Gamma-ray Burst Hubble Diagram: Promises and LimitationsWe present a complete sample of 29 gamma-ray bursts (GRBs) for which it has been possible to determine temporal breaks (or limits) from their afterglow light curves. We interpret these breaks within the framework of the uniform conical jet model, incorporating realistic estimates of the ambient density and propagating error estimates on the measured quantities. In agreement with our previous analysis of a smaller sample, the derived jet opening angles of those 16 bursts with redshifts result in a narrow clustering of geometrically corrected gamma-ray energies about 1.33 x 10(exp 51) ergs; the burst-to-burst variance about this value is 0.35 dex, a factor of 2.2. Despite this rather small scatter, we demonstrate in a series of GRB Hubble diagrams that the current sample cannot place meaningful constraints upon the fundamental parameters of the universe. Indeed, for GRBs to ever be useful in cosmographic measurements, we argue the necessity of two directions. First, GRB Hubble diagrams should be based upon fundamental physical quantities such as energy, rather than empirically derived and physically ill-understood distance indicators (such as those based upon prompt burst time-profiles and spectra). Second, a more homogeneous set should be constructed by culling subclasses from the larger sample. These subclasses, although now first recognizable by deviant energies, ultimately must be identifiable by properties other than those directly related to energy. We identify a new subclass of GRBs (" f-GRBs ") that appear both underluminous by factors of at least 10 and exhibit a rapid fading (f(sub nu is proportional to t(sup -2) at early times (t < or = 0.5 day). About 10%-20% of observed long-duration bursts appear to be f-GRBs.
Document ID
20050160221
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Bloom, J. S.
(Harvard-Smithsonian Center for Astrophysics Cambridge, MA, United States)
Frail, D. A.
(National Radio Astronomy Observatory Socorro, NM, United States)
Kulkarni, S. R.
(California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
August 23, 2013
Publication Date
September 10, 2003
Publication Information
Publication: The AStrophysical Journal
Publisher: Chicago Univ. Press
Volume: 594
Issue: Pt. 1
Subject Category
Astrophysics
Distribution Limits
Public
Copyright
Public Use Permitted.
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