TITLE:   GCN CIRCULAR
NUMBER:  28447
SUBJECT: GRB 200917A: Swift-BAT refined analysis
DATE:    20/09/17 21:05:06 GMT
FROM:    Tilan Ukwatta at LANL  <tilan.ukwatta@gmail.com>

C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI),  H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
E. Sonbas (Adiyaman Univ.), M. Stamatikos (OSU),
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 200917A (trigger #996184)
(Sonbas, et al., GCN Circ. 28435).  The BAT ground-calculated
position is RA, Dec = 235.742, -4.695 deg which is
   RA(J2000)  =  15h 42m 58.0s
   Dec(J2000) = -04d 41' 41.4"
with an uncertainty of 2.0 arcmin, (radius, sys+stat,
90% containment). The partial coding was 96%.

The mask-weighted light curve shows two peaks, a weak peak
at ~T-10 s and a stronger peak at ~T+5 s. T90 (15-350 keV) is
19.4 +- 2.9 sec (estimated error including systematics).

The time-averaged spectrum from T-15.76 to T+6.18 sec is best
fit by a simple power-law model.  The power law index of the
time-averaged spectrum is 2.24 +- 0.31.  The fluence in the
15-150 keV band is 3.0 +- 0.6 x 10^-07 erg/cm2. The 1-sec peak
photon flux measured from T+5.04 sec in the 15-150 keV band
is 0.6 +- 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/996184/BA/