TITLE: GCN CIRCULAR NUMBER: 33393 SUBJECT: GRB 230228A: Swift-BAT refined analysis DATE: 23/03/02 13:58:16 GMT FROM: Tyler Parsotan at UMBC/GSFC/CRESST II parsotat@umbc.edu

H. A. Krimm (NSF), S. D. Barthelmy (GSFC),

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 230228A (trigger #1156572)

(Dichiara, et al., GCN Circ. 33378). The BAT ground-calculated position is

RA, Dec = 18.397, 44.495 deg which is

RA(J2000) = 01h 13m 35.3s

Dec(J2000) = +44d 29' 41.9"

with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).

The partial coding was 78%.

The mask-weighted light curve shows a Fast Rise Exponential Decay single pulse.

T90 (15-350 keV) is 2.18 +- 0.40 sec (estimated error including systematics).

The time-averaged spectrum from T-0.05 to T+2.53 sec is best fit by a simple

power-law model. The power law index of the time-averaged spectrum is

1.66 +- 0.17. The fluence in the 15-150 keV band is 3.6 +- 0.4 x 10^-07 erg/cm2.

The 1-sec peak photon flux measured from T+0.18 sec in the 15-150 keV band

is 3.0 +- 0.4 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/1156572/BA/