GCN Circular 36459

H. A. Krimm (NSF), S. D. Barthelmy (GSFC),
S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa),
C. B. Markwardt (GSFC), M. J. Moss (GSFC),
D. M. Palmer (LANL), T. Parsotan (GSFC),
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 240511A (trigger #1227767)
(Laha et al., GCN Circ. 36430
Not found
 
 
).  The BAT ground-calculated position is
RA, Dec = 336.669, 8.515 deg which is
   RA(J2000)  =  22h 26m 40.6s
   Dec(J2000) = +08d 30' 54.4"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 85%.

The mask-weighted light curve shows a major pulse structure that
starts at ~T-50 s and ends at ~T+100 s. There are many smaller pulses
on top of the main pulse structure. The highest peak occurred at
~T+36 s. In addition, there are some weak emissions that start at
~T-100 s and end at ~T+200 s. We note that there are two obvious data
gaps within the T100 duration: (1) ~T+10 s to ~T+20 s and
(2) ~T+155 s to ~T+180 s. These data gaps may be filled by further
data downlink. T90 (15-350 keV) is 148.55 +- 20.07 sec (estimated
error including systematics).

The time-averaged spectrum from T-92.012 to T+ 203.704 sec is best fit
by a simple power-law model.  The power law index of the time-averaged
spectrum is 1.59 +- 0.04.  The fluence in the 15-150 keV band
is 1.06 +- 0.02 x 10^-5 erg/cm2. The 1-sec peak photon flux measured
from T+35.12 sec in the 15-150 keV band is 2.6 +- 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/1227767