TITLE:   GCN CIRCULAR
NUMBER:  40356
SUBJECT: GRB 250430A: Swift-BAT refined analysis
DATE:    25/05/06 02:50:20 GMT
FROM:    Mike Moss at NASA GSFC <mikejmoss3@gmail.com>

M. J. Moss (GSFC), S. D. Barthelmy (GSFC), 
R. Gupta (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), D. Sadaula (GSFC/UMBC),
T. Sakamoto (AGU) (i.e. the Swift-BAT team):
 
Using the data set from T-61 to T+242 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 250430A (trigger #1308754)
(Parsotan, et al., GCN Circ. 40292).  The BAT ground-calculated position is
RA, Dec = 233.395, -18.101 deg which is 
   RA(J2000)  =  15h 33m 34.7s 
   Dec(J2000) = -18d 06' 03.2" 
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 72%.
 
The mask-weighted light curve displays a double peaked structure.
The T90 (15-350 keV) is 9.17 +- 1.70 sec (estimated error including systematics).
 
The time-averaged spectrum from T+0.10 to T+11.86 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.66 +- 0.11.  The fluence in the 15-150 keV band is 8.9 +- 0.6 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T+0.31 sec in the 15-150 keV band
is 2.3 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 
 
The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1308754