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GCN Circular 31838

Subject
GRB 220404A: Swift-BAT refined analysis
Date
2022-04-06T01:13:25Z (2 years ago)
From
Takanori Sakamoto at AGU <tsakamoto@phys.aoyama.ac.jp>
C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC/UMBC),
T. Sakamoto (AGU), M. Stamatikos (OSU)
(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 220404A (trigger #1101133)
(Cenko, et al., GCN Circ. 31828).  The BAT ground-calculated position is
RA, Dec = 50.413, 10.001 deg which is
   RA(J2000)  =  03h 21m 39.0s
   Dec(J2000) = +10d 00' 03.4"
with an uncertainty of 2.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 47%.

The mask-weighted light curve shows a weak peak starts at T0 and ends at
T+3 s.  There is a hint of a emission around T+5 s. T90 (15-350 keV) is
2.54 +- 0.66 sec (estimated error including systematics).

The time-averaged spectrum from T+0.26 to T+2.98 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.90 +- 0.36.  The fluence in the 15-150 keV band is 1.4 +- 0.3 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+1.15 sec in the 15-150 keV band
is 1.1 +- 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/1101133/BA/
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