[vsnet-grb-info 20503] GRB 180404A: Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22599
SUBJECT: GRB 180404A: Swift-BAT refined analysis
DATE:    18/04/04 14:33:36 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto at phys.aoyama.ac.jp>

S. D. Barthelmy (GSFC), J. R. Cummings (CPI), J. D. Gropp (PSU),
H. A. Krimm (NSF/USRA), 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-239 to T+654 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 180404A (trigger #821881)
(Gropp, et al., GCN Circ. 22589).  The BAT ground-calculated position is
RA, Dec = 83.540, -37.168 deg which is
    RA(J2000)  =  05h 34m 09.5s
    Dec(J2000) = -37d 10' 05.0"
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 82%.
  
The mask-weighted light curve shows a weak emission that starts at T-25 sec,
followed by a bright peak which peaks at T+3 sec and ends at T+30 sec.
T90 (15-350 keV) is 35.2 +- 5.3 sec (estimated error including systematics).
  
The time-averaged spectrum from T-20.7 to T+24.2 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.95 +- 0.12.  The fluence in the 15-150 keV band is 1.3 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+1.99 sec in the 15-150 keV band
is 1.3 +- 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/821881/BA/