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GCN Circular 8312

Subject
Swift discovery of a new Soft Gamma Repeater SGR 1550-5418
Date
2008-10-03T11:46:01Z (15 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
H. A. Krimm (CRESST/GSFC/USRA), A. P. Beardmore (U Leicester),
N. Gehrels (NASA/GSFC), K. L. Page (U Leicester),
D. M. Palmer (LANL), R. L. C. Starling (U Leicester) and
T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:

At 11:16:13 UT, the Swift Burst Alert Telescope (BAT) triggered and
located a short soft burst (trigger=330367).   The BAT on-board 
calculated location is RA, Dec 237.704, -54.308 which is 
   RA(J2000) = 15h 50m 49s
   Dec(J2000) = -54d 18' 29"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  This is consistent with the location
of the trigger 330353, 108 minutes earlier.  The BAT light curve 
showed a single-peaked structure with a duration of about 0.750 sec, 
mostly below 100 keV.  The peak count rate was ~20000 counts/sec 
(15-350 keV), at ~0 sec after the trigger. 

Swift was already observing this source when BAT triggered. Hence, no XRT or UVOT
data will be downlinked via TDRSS, but will be available after the next Malindi pass. 

The earlier BAT trigger 330353 (Krimm et al. GCN 8311) showed
additional bursts at T+110s and T+520s, giving a total of
four known bursts from this source in under two hours.  Therefore
we believe that this is a new Soft Gamma Repeater, 
which we name SGR 1550-5418.  It is possible that this SGR
is the same source as the Anomalous X-ray Pulsar 1E1547.0-5408
(Gelfand & Gaensler 2007; Camilo et al. 2008; Halpern et al. 2008). 
This possible identification will be confirmed or refuted
when the XRT position data becomes available. 

Burst Advocate for this burst is H. A. Krimm (krimm AT milkyway.gsfc.nasa.gov). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)
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