TITLE:   GCN CIRCULAR
NUMBER:  34299
SUBJECT: GRB 230728A: Swift-BAT refined analysis
DATE:    23/07/31 12:57:17 GMT
FROM:    Tyler Parsotan  at NASA GSFC <tyler.parsotan@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-240 to T+962 sec from the recent telemetry downlink,

we report further analysis of BAT GRB 230728A (trigger #1181187)

(Salvaggio, et al., GCN Circ. 34282).  The BAT ground-calculated position is

RA, Dec = 343.514, 28.169 deg which is

   RA(J2000)  =  22h 54m 03.4s

   Dec(J2000) = +28d 10' 09.5"

with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).

The partial coding was 49%.



He mask-weighted light curve shows a complex multi-peaked structure with some

emission prior to the trigger time.

T90 (15-350 keV) is 15.10 +- 0.89 sec (estimated error including systematics).



The time-averaged spectrum from T-5.62 to T+10.74 sec is best fit by a simple

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

1.58 +- 0.13.  The fluence in the 15-150 keV band is 1.1 +- 0.1 x 10^-06 erg/cm2.

The 1-sec peak photon flux measured from T+0.41 sec in the 15-150 keV band

is 2.5 +- 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/1181187/BA/