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Observations of GRB 990123 by the Compton Gamma Ray ObservatoryGRB 990123 was the first burst from which simultaneous optical, X-ray, and gamma-ray emission was detected; its afterglow has been followed by an extensive set of radio, optical, and X-ray observations. We have studied the gamma-ray burst itself as observed by the Compton Gamma Ray Observatory detectors. We find that gamma-ray fluxes are not correlated with the simultaneous optical observations and that the gamma-ray spectra cannot be extrapolated simply to the optical fluxes. The burst is well fitted by the standard four-parameter GRB function, with the exception that excess emission compared with this function is observed below approx. 15 keV during some time intervals. The burst is characterized by the typical hard-to-soft and hardness-intensity correlation spectral evolution patterns. The energy of the peak of the vf (sub v), spectrum, E (sub p), reaches an unusually high value during the first intensity spike, 1470 plus or minus 110 keV, and then falls to approx. 300 keV during the tail of the burst. The high-energy spectrum above approx. 1 MeV is consistent with a power law with a photon index of about -3. By fluence, GRB 990123 is brighter than all but 0.4% of the GRBs observed with BATSE (Burst and Transient Source Experiment), clearly placing it on the -3/2 power-law portion of the intensity distribution. However, the redshift measured for the afterglow is inconsistent with the Euclidean interpretation of the -3/2 power law. Using the redshift value of greater than or equal to 1.61 and assuming isotropic emission, the gamma-ray energy exceeds 10 (exp 54) ergs.
Document ID
20000012413
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Briggs, M. S.
(Alabama Univ. Huntsville, AL United States)
Band, D. L.
(California Univ., San Diego La Jolla, CA United States)
Kippen, R. M.
(Alabama Univ. Huntsville, AL United States)
Preece, R. D.
(Alabama Univ. Huntsville, AL United States)
Kouveliotou, C.
(Universities Space Research Association Huntsville, AL United States)
vanParadijs, J.
(Alabama Univ. Huntsville, AL United States)
Share, G. H.
(Naval Research Lab. Washington, DC United States)
Murphy, R. J.
(Naval Research Lab. Washington, DC United States)
Matz, S. M.
(Northwestern Univ. Evanston, IL United States)
Connors, A.
(Wellesley Coll. MA United States)
Date Acquired
August 19, 2013
Publication Date
October 10, 1999
Publication Information
Publication: Astrophysical Journal
Publisher: American Astronomical Society
Volume: 524
Subject Category
Space Radiation
Funding Number(s)
CONTRACT_GRANT: DARA-50QV-90968
CONTRACT_GRANT: NAG5-6747
CONTRACT_GRANT: NAG5-7927
CONTRACT_GRANT: NAG5-7984
CONTRACT_GRANT: NAG5-7829
CONTRACT_GRANT: NAG5-7894
CONTRACT_GRANT: NAS5-26646
Distribution Limits
Public
Copyright
Other

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