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GCN Circular 273

Subject
GRB 990308a and GRB 990308b
Date
1999-03-10T16:17:22Z (25 years ago)
From
R. Marc Kippen at BATSE/UAH/MSFC <marc.kippen@msfc.nasa.gov>
Peter Woods, Marc Kippen, Georgia Richardson (UAH/MSFC), and Chryssa
Kouveliotou (USRA/MSFC) report on behalf of the BATSE team :

We have classified the two bursts mentioned in GCN 271 (BATSE triggers
7456 and 7460) as classical GRBs.  The first is a single pulse lasting
~ 0.5 sec with substructure and a very hard spectrum (photon index ~
-1).  The second event is much softer (photon index ~ -2) and longer
(~ 25 sec).  Although these bursts are positionally consistent with
one another (within 1 sigma), neither shows characteristics consistent
with any of the other known SGRs.  Their properties indicate they are
classical GRBs.

We have searched the DISCLA data for burst emission (1.024 sec time
resolution) at the Konus event times reported in GCN 271.  The
locations of triggers 7456 and 7460 are not occulted at the times
given for 990307, but no bursts are detected.  For 990308a, we detect
the trigger (7456) and a phosphorescence spike at T+45 sec.
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