TITLE:   GCN CIRCULAR
NUMBER:  21365
SUBJECT: GRB 170724A, Swift-BAT refined analysis
DATE:    17/07/26 00:30:05 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

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

Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 170724A (trigger #764204)
(Ukwatta et al., GCN Circ. 21364).  The BAT ground-calculated position is
RA, Dec = 150.057, -1.025 deg which is
  RA(J2000)  =  10h 00m 13.7s
  Dec(J2000) = -01d 01' 31.0"
with an uncertainty of 2.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 58%.

The mask-weighted light curve shows a weak complex structure that
starts at ~T-50 s and ends at ~T+80 s. T90 (15-350 keV) is 98.0 +- 26.1 sec
(estimated error including systematics).

The time-averaged spectrum from T-45.6 to T+63.6 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.46 +- 0.23.  The fluence in the 15-150 keV band is 1.1 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+35.92 sec in the 15-150 keV band
is 0.5 +- 0.2 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/764204/BA/