TITLE:   GCN CIRCULAR
NUMBER:  28506
SUBJECT: GRB 200925B: Swift-BAT refined analysis
DATE:    20/09/26 18:03:43 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

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

Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 200925B (trigger #997453)
(Cenko, et al., GCN Circ. 28499).  The BAT ground-calculated position is
RA, Dec = 246.892, 78.393 deg which is 
  RA(J2000)  =  16h 27m 34.1s 
  Dec(J2000) = +78d 23' 33.5" 
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 50%.

The mask-weighted light curve shows two peaks, the first beginning ~T-2 sec,
peaking at T+5 sec, and decaying by T+12 sec.  The second, weaker, peak runs
from T+16 to T+22 sec.  T90 (15-350 keV) is 18.25 +- 0.97 sec (estimated error 
including systematics).

The time-averaged spectrum from T+0.20 to T+19.59 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.01 +- 0.14.  The fluence in the 15-150 keV band is 1.0 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+4.38 sec in the 15-150 keV band
is 3.0 +- 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/997453/BA/