GCN Circular 22512

J. R. Cummings (CPI), S. D. Barthelmy (GSFC), 
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), A. Melandri (INAF-OAB),
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-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 180316A (trigger #814677)
(Melandri et al., GCN Circ. 22500
Not found
 
 
).  The BAT ground-calculated position is
RA, Dec = 265.422, 0.737 deg which is 
  RA(J2000)  =  17h 41m 41.3s 
  Dec(J2000) = +00d 44' 14.3" 
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 29%.

The mask-weighted light curve shows a main structure with several overlapping 
pulses that starts at ~ T-15 s and ends at ~ T+30 s. The major peak occurs at
~ T+1 s. In addition, there are some weak emission before the main structure 
that starts at ~ T-80 s, and a weak tail afterward that lasts until ~ T+40 s.
T90 (15-350 keV) is 87.0 +- 20.6 sec (estimated error including systematics).

The time-averaged spectrum from T-79.73 to T+37.27 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.46 +- 0.12.  The fluence in the 15-150 keV band is 4.9 +- 0.4 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+1.27 sec in the 15-150 keV band
is 3.3 +- 0.5 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.