[vsnet-grb-info 8564] GRB 091024: Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10072
SUBJECT: GRB 091024: Swift-BAT refined analysis
DATE:    09/10/24 17:40:10 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.gsfc.nasa.gov>

T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), F. E. Marshall (NASA/GSFC),
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+483 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 091024 (trigger #373674)
(Mashall, et al., GCN Circ. 10062).  The BAT ground-calculated position is
RA, Dec = 339.240, 56.885 deg, which is 
   RA(J2000)  =  22h 36m 57.6s 
   Dec(J2000) = +56d 53' 07.8" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 39%.
 
The mask-weighted light curve shows two slightly overlapping FRED peaks.
The first starts at ~T-20 sec, peaks at ~T+2 sec.  The second peaks at ~T+42 sec
and long-term low-level emission extends out to ~T+400 sec.
T90 (15-350 keV) is 109.8 +- 16.7 sec (estimated error including systematics).
 
The time-averaged spectrum from T-15.2 to T+135.8 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.20 +- 0.08.  The fluence in the 15-150 keV band is 6.1 +- 0.3 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-0.23 sec in the 15-150 keV band
is 2.0 +- 0.3 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/373674/BA/