TITLE:   GCN CIRCULAR
NUMBER:  28325
SUBJECT: GRB 200829A: Swift-BAT refined analysis
DATE:    20/08/30 17:01:36 GMT
FROM:    Sibasish Laha at GSFC  <sibasish.laha@nasa.gov>

D. M. Palmer (LANL), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), T. Sakamoto (AGU),
M. H. Siegel (PSU), 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 200829A (trigger #993768)
(Siegel, et al., GCN Circ. 28307).  The BAT ground-calculated position is
RA, Dec = 251.136, 72.363 deg which is
   RA(J2000)  =  16h 44m 32.7s
   Dec(J2000) = +72d 21' 45.6"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 88%.


The mask weighted light curve shows a peak at ~ T-60 s followed by an extended emission.
The duration of the initial bright peak is ~15 sec. We note that Swift was slewing from T-150 s to T s.
The overall structure starts at ~T-75 s and lasts till ~T+200 s.
T90 (15-350 keV) is 13.04 +- 2.91 sec (estimated error including systematics).

The time-averaged spectrum from T-74 to T+204 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
0.83 +- 0.03.  The fluence in the 15-150 keV band is 5.1 +- 0.1 x 10^-5 erg/cm2.
The 1-sec peak photon flux measured from T-60.07 sec in the 15-150 keV band
is 98.7 +- 1.6 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/993768/BA/