TITLE:   GCN CIRCULAR
NUMBER:  37155
SUBJECT: GRB 240811A: Swift-BAT refined analysis
DATE:    24/08/12 18:07:11 GMT
FROM:    Tyler Parsotan  at NASA GSFC <tyler.parsotan@nasa.gov>

A. Y. Lien (U Tampa), S. D. Barthelmy (GSFC),

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

S. Laha (GSFC/UMBC), 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-60 to T+243 sec from the recent telemetry downlink,

we report further analysis of BAT GRB 240811A (trigger #1248132)

(Page, et al., GCN Circ. 37136).  The BAT ground-calculated position is

RA, Dec = 226.328, 28.884 deg which is

   RA(J2000)  =  15h 05m 18.8s

   Dec(J2000) = +28d 53' 02.5"

with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).

The partial coding was 71%.



The mask-weighted light curve shows a complex structure with many peaks and

potential precursor emission ~30 seconds before the trigger time.

T90 (15-350 keV) is 66.32 +- 5.22 sec (estimated error including systematics).



The time-averaged spectrum from T-42.95 to T+41.32 sec is best fit by a simple

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

1.71 +- 0.08.  The fluence in the 15-150 keV band is 3.0 +- 0.1 x 10^-06 erg/cm2.

The 1-sec peak photon flux measured from T+11.30 sec in the 15-150 keV band

is 2.9 +- 0.3 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/1248132