TITLE:   GCN CIRCULAR
NUMBER:  33722
SUBJECT: GRB 230427A: Swift-BAT refined analysis
DATE:    23/05/03 22:26:28 GMT
FROM:    Sibasish Laha at GSFC <sibasish.laha@nasa.gov>

M. Stamatikos (OSU), S. D. Barthelmy (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), (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 230427A (trigger #1165948)
(Troja et al., GCN Circ. 33687).  The BAT ground-calculated position is
RA, Dec = 153.339, 48.231 deg which is
   RA(J2000)  =  10h 13m 21.5s
   Dec(J2000) = +48d 13' 52.3"
with an uncertainty of 3.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 86%.

The BAT light curve showed a complex structure with a duration of about 20 sec.
T90 (15-350 keV) is 4.00 +- 1.41 sec (estimated error including systematics).

The time-averaged spectrum from T-0.17 to T+3.83 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.36 +- 0.47.  The fluence in the 15-150 keV band is 9.5 +- 2.9 x 10^-08 erg/cm2.
The 1-sec peak photon flux measured from T-0.17 sec in the 15-150 keV band
is 0.7 +- 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/1165948/BA/