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GCN Circular 10528

Swift-BAT refined analysis of the probable new SGR 1833-0832
2010-03-19T22:55:16Z (14 years ago)
Scott Barthelmy at NASA/GSFC <>
S. D. Barthelmy (GSFC), T. Sakamoto (GSFC/UMBC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), J. M. Gelbord (PSU),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-239 to T+303 sec from the recent telemetry downlink,
we report further analysis of BAT trigger #416485 (Gelbord, et al., GCN Circ.
10526).  The BAT ground-calculated position is RA, Dec = 278.446, -8.533 deg,
which is 
   RA(J2000)  =  18h 33m 47.1s 
   Dec(J2000) = -08d 32' 00.2" 
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 87%.
The mask-weighted light curve shows two resolved peaks with a total duration
of ~16 millisec.  T90 (15-350 keV) is 0.012 +- 0.009 sec (estimated error
including systematics).
The time-averaged spectrum from T+0.000 to T+0.016 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index -1.02 +- 1.35, 
and Epeak of 38.2 +- 5.0 keV (chi squared 43.5 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 1.3 +- 0.2 x 10^-8 erg/cm2
and the 1-sec peak flux measured from T-0.49 sec in the 15-150 keV band is
0.2 +- 0.1 ph/cm2/sec.  Similarly, a blackbody fit yields kT= 10.0 +-1.2 keV
(chi squared 43.8 for 57 d.o.f).  A fit to a simple power law gives a photon index
of 2.58 +- 0.23 (chi squared 74.2 for 57 d.o.f.).  All the quoted errors
are at the 90% confidence level. 
The results of the batgrbproduct analysis are available at
Given (a) the low galactic lattitude (0.01 deg), (b) the short duration
of the event, and (c) the spectral softness (Epeak=38.2 and photon index
of -1.02), we believe this to be an event from a new probable SGR
which we are calling SGR 1833-0832.
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