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GCN Circular 14373

Subject

GRB 130408A, Swift-BAT refined analysis

Date

2013-04-09T23:45:37Z (12 years ago)

From

Craig Markwardt at NASA/GSFC <craigm@milkyway.gsfc.nasa.gov>

W. H. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (NASA/GSFC/ORAU),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC),
G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC),
T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):

Using the data set from T-240 to T+960 sec from the recent telemetry 
downlink, we report further analysis of BAT GRB 130408A (trigger 
#553132) (Lien, et al., GCN Circ. 14361Not found
 
 
).  The BAT ground-calculated 
position is
RA, Dec = 134.398, -32.363 deg which is
    RA(J2000)  =  08h 57m 35.5s
    Dec(J2000) = -32d 21' 45.9"
with an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment). 
The partial coding was 6%.

T90 (15-350 keV) is 28 +- 13 sec (estimated error including 
systematics).  The mask weighted light curve has a main FRED-like 
component with a rise time of about 2 sec and decline of 5 sec, peaking 
at time T+1 sec, followed by a smaller peak at T+12 sec.  There is 
possible low-level emission out to about T+33 sec.

The time-averaged spectrum from T-0.1 to T+33.5 sec is best fit by a 
simple power-law model.  The power law index of the time-averaged 
spectrum is 1.28 +- 0.26.  The fluence in the 15-150 keV band is 2.3 +- 
0.4 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+1.12 sec 
in the 15-150 keV band is 4.9 +- 1.0 ph/cm2/sec.  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/553132/BA/