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GCN Circular 19596

Subject

Swift-BAT refined analysis on the bright event from SGR 1935+2154

Date

2016-06-27T01:23:34Z (8 years ago)

From

Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>

J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
 
Using the data set from T-119 to T+76 sec from the recent telemetry downlinks,
we report further analysis of the bright event from SGR 1935+2154 (trigger #701590)
(Barthelmy, et al., GCN Circ. 19590Not found
 
 
).  The BAT ground-calculated position is
RA, Dec = 293.730, 21.887 deg, which is 
   RA(J2000)  =  19h 34m 55.3s 
   Dec(J2000) = +21d 53' 14.6" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 82%.
 
The mask-weighted light curve shows a very rectangular profile starting at ~T-0.15 sec
and ending at ~T+0.7 sec.  T90 (15-350 keV) is 0.680 +- 0.004 sec (estimated error
including systematics).
 
The time-averaged spectrum from T-0.22 to T+0.67 sec best fit by a double blackbody
with a lower temperature of 7.60 +- 0.42 keV and the higher temperature of 14.25 +- 0.89 keV
(chi squared 40.9 for 55 d.o.f.).  For reference, the simple power-law model yields
a power law index of 3.09 +- 0.02 (chi squared 2025 for 57 d.o.f.).
All the quoted errors are at the 90% confidence level.
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/701590/BA/