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GCN Circular 31968

Subject

GRB 220427A: Swift-BAT refined analysis

Date

2022-04-29T13:45:22Z (2 years ago)

From

Amy Lien at GSFC <amy.y.lien@nasa.gov>

M. Stamatikos (OSU) S. D. Barthelmy (GSFC),
A. D'Ai (INAF-IASFPA), 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)
(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 220427A (trigger #1104343)
(D'Ai et al., GCN Circ. 31960Not found
 
 
).  The BAT ground-calculated position is
RA, Dec = 275.922, -56.257 deg which is
   RA(J2000)  =  18h 23m 41.2s
   Dec(J2000) = -56d 15' 23.7"
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 62%.

The mask-weighted light curve shows a single-peaked structure that
starts at ~T+3 s and peaks at ~T+8 s, and followed by a long tail
emission that ends at ~T+70 s. T90 (15-350 keV) is 57.2 +- 12.2 sec
(estimated error including systematics).

The time-averaged spectrum from T+3.09 to T+68.06 sec is best fit
by a simple power-law model.  The power law index of the time-averaged
spectrum is 1.23 +- 0.13.  The fluence in the 15-150 keV band is
2.1 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from
T+7.83 sec in the 15-150 keV band is 3.0 +- 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/1104343/BA/