[vsnet-grb-info 19349] GRB 170428A: Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21046
SUBJECT: GRB 170428A: Swift-BAT refined analysis
DATE:    17/04/28 21:04:52 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm at nsf.gov>

S. D. Barthelmy (GSFC),  A. P. Beardmore (U Leicester), J. R. Cummings (CPI),
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
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-119 to T+303 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 170428A (trigger #750298)
(Beardmore, et al., GCN Circ. 21042).  The BAT ground-calculated position is
RA, Dec = 330.051, 26.913 deg which is 
  RA(J2000)  =  22h 00m 12.3s 
  Dec(J2000) = +26d 54' 47.9" 
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 62%.

The mask-weighted light curve shows a complex of three peaks within a period 
from T+0.15 to T+0.35 sec.   There is no sign of extended emission.
T90 (15-350 keV) is 0.20 +- 0.07 sec (estimated error including systematics).

The time-averaged spectrum from T+0.15 to T+0.45 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
0.76 +- 0.12.  The fluence in the 15-150 keV band is 2.8 +- 0.2 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.20 sec in the 15-150 keV band
is 2.8 +- 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/750298/BA/