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GCN Circular 271

GRB990308, Possible new SGR~0209+70
1999-03-08T22:07:34Z (25 years ago)
David Palmer at USRA/GSFC <>
On behalf of the Konus team, David Palmer writes:

Konus has detected two series of short spike bursts (typically shorter
than the 64 ms sampling time) on 1999 March 7 & 8.  One such series
begins on 990307 at Seconds of Day (SOD) 62019.5, with subsequent bursts
at +12, +20, +57 (double spike), +72, and +87 (positive flux in 4
consecutive 64 ms samples) seconds later.  The fine time resolution
sampling ends at +100 seconds.  The spikes at +20 and +87 seconds each
exceed 200 counts per sample.

The second series begins at 990308 SOD 11094.5, with a complex burst,
with subsequent peaks at +2, +6, +21 and +28 seconds.

The initial burst of the second series corresponds to BATSE #7456
(990308_11093), which has a final estimated position of (RA, dec) =
(24.8,+67.8) degrees J2000. This is just barely above the horizon as
seen by BATSE at that time, and subsequent spikes may have been blocked
by Earth occultation.

BATSE #7460 (990308_71254) has a final position of (RA,Dec)=(39.8,+71.6)
or 6 degrees away from the final BATSE #7456 position.  This is
consistent with the measurement accuracy, and improbable for two
independent bursts on the same day at better than the 95% level, with
the usual caveats about post-prior probabilities.  The mean location is
8 degrees from the Galactic plane.

All of these properties are consistent with a proposed source
identification as a previously-unknown SGR.

Observations of this sky location with other high-energy instruments are

            David Palmer
           USA    (301) 286-2739  Voice  
           USA    (301) 286-1684  Fax
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