AAS 201st Meeting, January, 2003
Session 69. Gamma Ray Observations
Oral, Tuesday, January 7, 2003, 2:00-3:30pm, 616-617

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[69.04] Evidence for Postquiescent, High-Energy Emission from Gamma-Ray Burst 990104

D. N. Wren (Department of Physics, University of Maryland College Park; and Laboratory for High Energy Astrophysics, NASA/Goddard Space Flight Center), D. L. Bertsch, S. Ritz (Laboratory for High Energy Astrophysics, NASA/Goddard Space Flight Center)

It is well known that high-energy emission (MeV-GeV) has been observed in a number of gamma-ray bursts, and temporally extended emission from lower energy gamma rays through radio wavelengths is well established. An important observed characteristic of some bursts at low energy is quiescence: an initial emission followed by a quiet period before a second (postquiescent) emission. However, evidence for significant high-energy, postquiescent emission had been lacking until GRB 990104. Here we present evidence for high-energy emission, coincident with lower energy emission, from the postquiescent emission episode of the very bright and long burst, GRB 990104. We show light curves and spectra that confirm emission above 50 MeV, approximately 152 s after the BATSE trigger and initial emission episode. Between the initial emission episode and the main peak, seen at both low and high energy, there was a quiescent period of ~100 s. This burst was found as part of a search for high-energy emission in gamma-ray bursts using the EGRET fixed interval (32 s) accumulation spectra, which provide sensitivity to later, high-energy emission that is otherwise missed by the standard EGRET BATSE-triggered burst spectra. It has been known for some time that an exciting question for the upcoming GLAST era is the behavior of the high-energy emission observed minutes or more after the initial emission. The characteristics of GRB 990104 support the necessity of extended observations. These results were summarized in ApJL 574:L47-L50.

If you would like more information about this abstract, please follow the link to http://arxiv.org/abs/astro-ph/0206342. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.

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