TITLE:   GCN CIRCULAR
NUMBER:  23273
SUBJECT: GRB 180925A: Swift-BAT refined analysis
DATE:    18/09/26 03:39:29 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

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

Using the data set from T-240 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 180925A (trigger #863421)
(Gropp et al., GCN Circ. 23268).  The BAT ground-calculated position is
RA, Dec = 315.212, -64.450 deg which is
  RA(J2000)  =  21h 00m 50.9s
  Dec(J2000) = -64d 26' 59.2"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 15%.

The mask-weighted light curve shows a multi-peaked structure that starts
at ~T-5 s and ends at ~T+105 s. The main peak occurs at ~ T+1 s.
T90 (15-350 keV) is 81.70 +- 23.25 sec (estimated error including systematics).

The time-averaged spectrum from T-4.44 to T+103.96 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.53 +- 0.13.  The fluence in the 15-150 keV band is 4.1 +- 0.3 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.87 sec in the 15-150 keV band
is 3.1 +- 0.6 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/863421/BA/