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ADS Astronomy Abstract Service

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 Title:              MeV Measurements of Gamma-Ray Bursts by CGRO-COMPTEL
 Authors:            CONNORS, A.; KAPPADATH, S.; MCCONNELL, M.;
                     RYAN, J.M.; YOUNG, C.A.; BENNETT, K.;
                     WILLIAMS, O.R.; WINKLER, C.; COLLMAR, W.;
                     SCHONFELDER, V.; VARENDORFF, M.; HERMSEN, W.;
                     KUIPER, L.; KIPPEN, R.M.
 Affiliation:        AA(Space Science Center, U. New Hampshire),
                     AF(Astrophysics Division, ESTEC), AI(MPI fur
                     Extraterrestrische Physik), AL(SRON-Utrecht),
                     AN(C.S.P.A.R., U. Alabama)
 Journal:            Bull. American Astron. Soc., 191, #48.01
 Publication Date:   12/1997
 Origin:             AAS
 Abstract Copyright: (c) 1997: American Astronomical Society
 Bibliographic Code: 1997AAS...191.4801C

                                  Abstract

Since the launch of the Compton Gamma--Ray Observatory in April 1991, the
imaging COMPTEL telescope has accumulated positions and 0.75--30 MeV spectra
of thirty-three gamma-ray bursts within its Pi sr field of view.
BATSE (and Konus) data have shown some evidence for two classes of burst
emission, based on presence (HE) or lack (NHE) of flux >300 keV (Pendleton
et al. 1996 and references therein). Piran and Naryan (1996) suggest
MeV--bright bursts may be undercounted by BATSE. COMPTEL preferentially
measures this potentially interesting subclass. We will present the latest
spatial, spectral, and temporal distributions of these events. These include
the spectra of GRB 961212 and the soft faint burst GRB 970807. Like most
bursts observed by COMPTEL, their spectra appear to be well--represented by
power-law models with photon indexes ~ 2.1 and ~ 3.0, respectively. Also,
COMPTEL broadcasts the 1-2 degree localizations within 8-15 minutes of burst
onset, via ongoing collaboration with BACODINE/GCN network. The COMPTEL
positions of two of the most recent bursts, GRB 961212 and GRB 970807, were
relayed to a global network of multiwavelength observers in 15 and 45
minutes, respectively. In the future, we plan to upgrade the system,
potentially allowing us to broadcast 1-2 degree localizations within a few
minutes of burst onset. Such rapid response raises the possibility of
multi-wavelength observations of particularly bright, well-suited, bursts,
while the high energy emission is still underway.

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