TITLE:   GCN CIRCULAR
NUMBER:  22474
SUBJECT: GRB 180311A, Swift-BAT refined analysis
DATE:    18/03/12 13:00:00 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

M. Stamatikos (OSU), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), K. L. Page (U Leicester),
T. Sakamoto (AGU), 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 180311A (trigger #813721)
(Page et al., GCN Circ. 22468).  The BAT ground-calculated position is
RA, Dec = 3.379, -54.491 deg which is
  RA(J2000)  =  00h 13m 31.0s
  Dec(J2000) = -54d 29' 26.6"
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 94%.

The mask-weighted light curve shows a single-peaked structure that starts
at ~ T0, peaks at ~T+3 s, and ends at ~T+26 s. T90 (15-350 keV) is
23.0 +- 8.7 sec (estimated error including systematics).

The time-averaged spectrum from T-0.2 to T+26.6 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.78 +- 0.29.  The fluence in the 15-150 keV band is 3.3 +- 0.7 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+2.88 sec in the 15-150 keV band
is 0.6 +- 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/813721/BA/