TITLE:   GCN CIRCULAR
NUMBER:  22561
SUBJECT: GRB 180329A: Swift-BAT refined analysis
DATE:    18/03/29 22:26:04 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF/USRA),
A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL),
J. L. Racusin (NASA/GSFC), 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+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 180329A (trigger #819301)
(Racusin et al., GCN Circ. 22556).  The BAT ground-calculated position is
RA, Dec = 329.314, -15.043 deg which is
  RA(J2000)  =  21h 57m 15.3s
  Dec(J2000) = -15d 02' 36.0"
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 80%.

The mask-weighted light curve shows a weak pulse that starts at ~T0, peaks
at ~T+1 s, and ends at ~T+10 s. T90 (15-350 keV) is 9.1 +- 1.8 sec (estimated
error including systematics).

The time-averaged spectrum from T-0.30 to T+9.69 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.39 +- 0.31.  The fluence in the 15-150 keV band is 2.3 +- 0.4 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+1.14 sec in the 15-150 keV band
is 0.5 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

Due to an observing constraint, there are no observations of this source with the
Swift XRT or UVOT, and hence no confirmation of the nature of the source.
However, because the image significance from the ground analysis of the BAT
data is ~ 9 sigma, and the temporal and spectral properties are consistent with
those from a BAT GRB, we conclude that this source is likely a real GRB.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/819301/BA/