TITLE:   GCN CIRCULAR
NUMBER:  22533
SUBJECT: GRB 180324A, Swift-BAT refined analysis
DATE:    18/03/25 02:06:18 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

H. A. Krimm (NSF/USRA), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), J. P. Norris (BSU),
D. M. Palmer (LANL), T. Sakamoto (AGU),
E. Sonbas (Adiyaman Univ.), 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 180324A (trigger #817345)
(Sonbas et al., GCN Circ. 22524).  The BAT ground-calculated position is
RA, Dec = 76.581, 56.744 deg which is
  RA(J2000)  =  05h 06m 19.4s
  Dec(J2000) = +56d 44' 36.8"
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 78%.

The mask-weighted light curve shows a small precursor at ~T-5 s, followed
by the main pulse that starts at ~T-0.2, peaks at ~T+0.3 s, and ends at ~T+1 s.
There is also some weak emission that lasts till ~T+4 s. T90 (15-350 keV)
is 7.2 +- 1.3 sec (estimated error including systematics).

The lag analysis for the main pulse finds a lag of 48 +- 18 ms for the
100-350 keV to 25-100 keV band. This value is consistent with that of a
long GRB. In addition, no extended emission is found after ~T+4 s.

The time-averaged spectrum from T-5.4 to T+3.7 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.45 +- 0.14.  The fluence in the 15-150 keV band is 5.6 +- 0.5 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.13 sec in the 15-150 keV band
is 4.4 +- 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/817345/BA/