[vsnet-grb-info 20505] GRB 180404B: Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22601
SUBJECT: GRB 180404B: Swift-BAT refined analysis
DATE:    18/04/04 20:39:26 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien at nasa.gov>

J. R. Cummings (CPI), S. D. Barthelmy (GSFC),
H. A. Krimm (NSF/USRA), S. J. LaPorte (PSU),
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-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 180404B (trigger #821902)
(LaPorte et al., GCN Circ. 22590).  The BAT ground-calculated position is
RA, Dec = 53.390, -50.213 deg which is
  RA(J2000)  =  03h 33m 33.6s
  Dec(J2000) = -50d 12' 47.4"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 84%.

The mask-weighted light curve shows a major pulse that starts at ~ T-6 s and peaks
at ~ T+ 10 s. Another weaker pulse arises at the end of the major pulse at ~ T+40 s.
The second pulse peaks at ~ T+50 s and lasts until ~ T+200 s. T90 (15-350 keV)
is 111.5 +- 7.1 sec (estimated error including systematics).

The time-averaged spectrum from T-5.91 to T+195.64 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.35 +- 0.04.  The fluence in the 15-150 keV band is 1.20 +- 0.02 x 10^-5 erg/cm2.
The 1-sec peak photon flux measured from T+8.88 sec in the 15-150 keV band
is 5.2 +- 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/821902/BA/