[vsnet-grb-info 15432] GRB 140818B, Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16721
SUBJECT: GRB 140818B, Swift-BAT refined analysis
DATE:    14/08/19 19:08:38 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien at nasa.gov>

H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), A. Y. Lien (NASA/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (LANL)
A. Vargas (PSU) (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 140818B (trigger #609885)
(Vargas, et al., GCN Circ. 16709).  The BAT ground-calculated position is
RA, Dec = 271.168, -1.354 deg which is
  RA(J2000)  =  18h 04m 40.2s
  Dec(J2000) = -01d 21' 14.3"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 39%.

The mask-weighted light curve shows a single-peaked structure starts at ~T-4 sec and
peaks at ~ T+1 sec. The main pulse ends at ~T+2 sec, with some weak emission lasting
till ~T+18 sec. T90 (15-350 keV) is 18.1 +- 5.0 sec (estimated error including systematics).

The time-averaged spectrum from T-3.5 to T+18.1 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.99 +- 0.25.  The fluence in the 15-150 keV band is 5.4 +- 0.8 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.31 sec in the 15-150 keV band
is 1.1 +- 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/609885/BA/