| Authors | M.S. Briggs, D.L. Band, R.M. Kippen, R.D. Preece, C. Kouveliotou, J.A. van Paradijs, G.H. Share, R.J. Murphy, S.M. Matz, A. Connors, C. Winkler, M.L. McConnel, J.M. Ryan, O.R. Williams, C.A. Young, B. Dingus, J.R. Catelli, R.A.M.J. Wijers | | Title | Observations of GRB 990123 by the Compton gamma ray observatory |
| Journal | Astrophysical Journal |
| Volume | 524 |
| Year | 1999 |
| Issue | 1 |
| Pages | 82-91 |
| ISSN | 0004637X |
| Faculty | Faculty of Science |
| Institute/dept. | FNWI: Astronomical Institute Anton Pannekoek (IAP) |
| Keywords | Gamma ray bursts; X-ray bursts |
| Abstract | GRB 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 ~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 nuf_nu spectrum, E_p, reaches an unusually high value during the first intensity spike, 1470+/-110 keV, and then falls to ~300 keV during the tail of the burst. The high-energy spectrum above ~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, 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 >=1.61 and assuming isotropic emission, the gamma-ray energy exceeds 10^54 ergs. |
| Note | ©1999 The American Astronomical Society |
| Document type | Article |
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