TITLE:   GCN CIRCULAR
NUMBER:  21473
SUBJECT: GRB 170813A: Swift-BAT refined analysis
DATE:    17/08/14 01:33:07 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

D. M. Palmer (LANL), S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL), T. Sakamoto (AGU),
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 170813A (trigger #767563)
(Page, et al., GCN Circ. 21468).  The BAT ground-calculated position is
RA, Dec = 201.057, -5.527 deg which is
 RA(J2000)  =  13h 24m 13.7s
 Dec(J2000) = -05d 31' 37.4"
with an uncertainty of 3.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 71%.

The mask-weighted light curve shows a initial ragged pulse with a fast rise starting
at about T-10 sec, peaking at T+3 sec and then decaying to near background by
T+40, followed by a second weaker pulse from T+40 to T+80 sec.
T90 (15-350 keV) is 75.5 +- 10.9 sec (estimated error including systematics).

The time-averaged spectrum from T-9.2 to T+78.9 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.17 +- 0.14.  The fluence in the 15-150 keV band is 1.9 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+2.64 sec in the 15-150 keV band
is 0.8 +- 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/767563/BA/