TITLE:   GCN CIRCULAR
NUMBER:  37154
SUBJECT: GRB 240809A: Swift-BAT refined analysis
DATE:    24/08/12 18:06:35 GMT
FROM:    Tyler Parsotan  at NASA GSFC <tyler.parsotan@nasa.gov>

S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC),

R. Gupta (GSFC), H. A. Krimm (NSF),

A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),

M. J. Moss (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-240 to T+963 sec from the recent telemetry downlink,

we report further analysis of BAT GRB 240809A (trigger #1247745)

(Evans, et al., GCN Circ. 37110).  The BAT ground-calculated position is

RA, Dec = 237.545, -2.331 deg which is

   RA(J2000)  =  15h 50m 10.8s

   Dec(J2000) = -02d 19' 51.1"

with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).

The partial coding was 72%.



The mask-weighted light curve shows a single peaked fast rise exponential decay

structure with a tail that lasts until ~100 seconds after the trigger time.

T90 (15-350 keV) is 72.86 +- 19.39 sec (estimated error including systematics).



The time-averaged spectrum from -10.876 to 180.52 sec is best fit by a simple

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

1.17 +- 0.05.  The fluence in the 15-150 keV band is 9.7 +- 0.2 x 10^-06 erg/cm2.

The 1-sec peak photon flux measured from T+2.68 sec in the 15-150 keV band

is 12.8 +- 0.4 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/1247745