[vsnet-grb-info 13891] GRB 130907A: Further Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15205
SUBJECT: GRB 130907A:  Further Swift-BAT refined analysis
DATE:    13/09/09 19:41:01 GMT
FROM:    Hans Krimm at NASA-GSFC  <hans.krimm at nasa.gov>

H. A. Krimm (GSFC/USRA), J. R. Cummings (GSFC/UMBC), D. M. Palmer (LANL),
C. B. Markwardt (GSFC) for the Swift-BAT team):

Using the complete data set from T-239 to T+963 sec, we report further analysis 
of BAT GRB 130907A (trigger #569992) (Page, et al., GCN Circ. 15183).  The 
initial report on the BAT data was presented in Cummings, et al., GCN Circ. 15202.

The burst started while Swift was slewing from another target, and the burst 
location came into the BAT coded field of view at about T-80 seconds. The 
initial pair of peaks at T-117 that triggered Konus-Wind (Golenetskii, et al., 
GCN Circ. 15203) and INTEGRAL/SPI-ACS  (Savchenko, et al., GCN Circ. 15204) were 
seen from outside the coded field in the non-weighted rates.

The mask-weighted light curve is described in Cummings, et al., GCN Circ. 15202. 
Although there are no discrete peaks later than T+240 seconds, the burst is 
still detected in the mask-weighted rate out to T+963 sec, when this data cuts 
off and continues to be detected onboard in a 64-second image starting at 
T+1388, and possibly later.  Since the BAT event data does not cover the full 
extent of the burst, we cannot reliably calculate T90 at this point, but it is 
at least 360 seconds.

The time-averaged spectrum from T-73.7 to T+767.4 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.17 +- 0.02.  The fluence in the 15-150 keV band is 1.4 +- 0.01 x 10^-4 
erg/cm2. We note that this time interval does not cover the entire burst 
duration, so should be considered a lower limit.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/569992/BA/