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GCN Circular 20923

Subject

GRB 170318B: Swift-BAT refined analysis

Date

2017-03-20T01:21:46Z (8 years ago)

From

Hans Krimm at NASA-GSFC/NSF <hans.krimm@nasa.gov>

H. A. Krimm (NSF/USRA), S. D. Barthelmy (GSFC), A. Cholden-Brown (PSU),
J. R. Cummings (CPI), N. Gehrels (GSFC), 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-239 to T+963 sec from the recent telemetry 
downlink,
we report further analysis of BAT GRB 170318B (trigger #743086)
(Cholden-Brown, et al., GCN Circ. 20908Not found
 
 
).  The BAT ground-calculated 
position is
RA, Dec = 284.229, 6.335 deg which is
    RA(J2000)  =  18h 56m 54.9s
    Dec(J2000) = +06d 20' 04.5"
with an uncertainty of 3.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 67%.

The mask-weighted light curve shows an initial symmetric pulse of 
duration ~20 sec
from about T-15 sec to T+5 sec.  This is followed by low-level extended 
emission from
~T+30 to T+160 sec. T90 (15-350 keV) is 160.0 +- 35.8 sec (estimated 
error including systematics).

The time-averaged spectrum from T-15.33 to T+160.67 sec is best fit by a 
simple
power-law model.  The power law index of the time-averaged spectrum is
1.84 +- 0.59.  The fluence in the 15-150 keV band is 5.5 +- 1.9 x 10^-7 
erg/cm2.
The 1-sec peak photon flux measured from T-7.83 sec in the 15-150 keV band
is 0.1 +- 0.1 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/743086/BA/