TITLE:   GCN CIRCULAR
NUMBER:  31993
SUBJECT: GRB 220501A: Swift-BAT refined analysis
DATE:    22/05/02 22:12:43 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

H. A. Krimm (NSF),S. D. Barthelmy (GSFC),
A. D'Ai (INAF-IASFPA), 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+816 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 220501A (trigger #1104842)
(D'Ai et al., GCN Circ. 31982).  The BAT ground-calculated position is
RA, Dec = 85.583, 14.010 deg which is
   RA(J2000)  =  05h 42m 20.0s
   Dec(J2000) = +14d 00' 36.5"
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 92%.

The mask-weighted light curve shows a FRED-like pulse that starts
at ~T-1 s and peaks at ~T+5 s. It is followed by a second weak pulse
at ~T+200 s. T90 (15-350 keV) is 202.24 +- 20.60 sec (estimated error
including systematics).

The time-averaged spectrum from T-1.21 to T+224.20 sec is best fit
by a power law with an exponential cutoff.  This fit gives a photon
index 0.64 +- 0.62, and Epeak of 72.3 +- 28.6 keV (chi squared 44.65
for 56 d.o.f.).  For this model the total fluence in the 15-150 keV
band is 2.2 +- 0.2 x 10^-6 erg/cm2 and the 1-sec peak flux measured
from T+4.28 sec in the 15-150 keV band is 1.2 +- 0.2 ph/cm2/sec.
 A fit to a simple power law gives a photon index of 1.54 +- 0.13
(chi squared 52.35 for 57 d.o.f.).  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/1104842/BA/