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IAUC 6518: gamma-RAY BURSTS; 22P

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                                                  Circular No. 6518
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
Phone 617-495-7244/7440/7444 (for emergency use only)

     C. Meegan, V. Connaughton and G. Fishman, NASA Marshall Space
Flight Center; R. M. Kippen, University of Alabama at Huntsville;
C. Kouveliotou, Universities Space Research Association; K. Hurley,
University of California at Berkeley; T. Cline, D. Palmer, S. Barthelmy,
P. Butterworth, B. Teegarden, H. Seifert and J. in't Zand, NASA Goddard
Space Flight Center; and E. Mazets and S. Golenetskij, Ioffe Institute
of Physics and Technology, report: "Several spacecraft have detected a
sequence of gamma-ray bursts over a two-day period with locations that are
consistent with a single source.  The following positions (equinox 2000.0)
have been determined by BATSE: Oct. 27.48897 UT, R.A. = 4h30m, Decl. =
-42d.4, uncertainty 5d.6, duration 100 s; 27.50141, 4h35m, -54d.3, 5d.8,
0.9 s (detection by Konus); 29.27404, 3h58m, -52d.6, 4d.6, 30 s (Konus);
29.28183, 3h59m, -48d.9, 0d.3, 750 s (Ulysses, TGRS and Konus).  The
proximity (i.e., the quadratic sum of the statistical errors, excluding
BATSE's systematic error of about 1.6 deg) of the first three BATSE event
locations to the fourth, including Interplanetary (IPN) locations using
BATSE, Ulysses and Konus, are 1.4, 3.0 and 1.0 deg, respectively.  The
Ulysses-BATSE IPN annulus is described by a center at R.A. = 23h46m.63,
Decl. = -31d24'.5 with a radius of 49.883 deg, fullwidth 0.078 deg.
The much wider Ulysses-Konus annulus defines the end points of the
Ulysses-BATSE annular segment at R.A. = 3h58m.9, Decl. = -47d04' and
R.A. = 4h01m.3, Decl. = -52d35' with a 99.7-percent confidence level.
A soft gamma repeater can be excluded as a common source by the durations
of the events, as well as by their spectra, which are consistent with
classical gamma-ray bursts.  The temporal structures of the events are
quite different, apparently ruling out a gravitational-lens interpretation.
The third and fourth events are very probably separate triggers from a
single burst, making the combined event the longest burst (1420 seconds)
ever seen in this energy range.  Although a posteriori calculations are
problematic, the probability of such a temporal and spatial coincidence
of four unrelated events is low."

     Total visual magnitudes (L = reflector):
Aug. 11.96 UT, 8.8 (J. Carvajal, Teruel, Spain, 0.21-m L); 22.23, 9.5
(C. E. Spratt, Victoria, BC, 0.20-m L); Sept. 3.89, 8.9 (J. M. San Juan,
Madrid, Spain, 0.21-m L); 17.87, 9.6 (J. M. Trigo, Castellon, Spain,
0.17-m L); Oct. 3.11, 11.2 (A. Hale, Cloudcroft, NM, 0.41-m L);
9.17, 12.1 (R. Keen, Mt. Thorodin, CO, 0.32-m L); Nov. 4.75, 13.0
(M. Plsek, Lelekovice, Czech Republic, 0.35-m L).

                      (C) Copyright 1996 CBAT
1996 December 9                (6518)              Brian G. Marsden

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