[vsnet-grb-info 13888] GRB 130907A, Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15202
SUBJECT: GRB 130907A, Swift-BAT refined analysis
DATE:    13/09/09 01:35:56 GMT
FROM:    Hans Krimm at NASA-GSFC  <hans.a.krimm at nasa.gov>

J. R. Cummings (GSFC/UMBC),S. D. Barthelmy (GSFC), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (GSFC),
M. J. Page (UCL-MSSL),D. M. Palmer (LANL),T. Sakamoto (AGU),
M. Stamatikos (OSU),J. Tueller (GSFC),T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):

Using the data set from T-60 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 130907A (trigger #569992)
(Page, et al., GCN Circ. 15183).  The BAT ground-calculated position is
RA, Dec = 215.898, 45.602 deg which is
    RA(J2000)  =  14h 23m 35.5s
    Dec(J2000) = +45d 36' 08.0"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows a very complicated structure with six main
peaks from T-55 sec to T+95 sec.  Each of these peaks shows several sub-peaks.
The strongest peak is at ~T+57 sec.  After T+95 sec, the count rate drops
significantly, but doesn't return all the way to the background level.  Then
there is another weak, soft peak from T+210 sec to T+240 sec. This late peak
is coincident with the start of a long flare seen in the XRT. There may be
further BAT emission beyond the end of the currently available event data.
T90 (15-350 keV) is 115.14 +- 0.67 sec (estimated error including systematics).

The time-averaged spectrum from T-50.7 to T+234.6 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.11 +- 0.02.  The fluence in the 15-150 keV band is 1.2 +- 0.0 x 10^-4 erg/cm2.
The 1-sec peak photon flux measured from T+57.66 sec in the 15-150 keV band
is 25.6 +- 0.5 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/569992/BA/