GCN Circular 35781

H. A. Krimm (NSF), S. D. Barthelmy (GSFC),
P. D'Avanzo (INAF-OAB), 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-60 to T+243 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 240222A (trigger #1216804)
(D'Avanzo et al., GCN Circ. 35770
Not found
 
 
).  The BAT ground-calculated position is
RA, Dec = 143.209, -68.034 deg which is
   RA(J2000)  =  09h 32m 50.2s
   Dec(J2000) = -68d 02' 03.7"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 94%.

The mask-weighted light curve shows a main pulse that starts
at ~T-0.4 s, peaks at ~T0, and ends at ~T+1.4 s. In addition,
there is a small precursor pulse at ~T-2.7 s. T90 (15-350 keV)
is 3.94 +- 2.35 sec (estimated error including systematics).

The time-averaged spectrum from T-2.70 to T+1.37 sec is best fit
by a simple power-law model.  The power law index of the time-averaged
spectrum is 0.75 +- 0.23.  The fluence in the 15-150 keV band
is 2.5 +- 0.3 x 10^-7 erg/cm2. The 1-sec peak photon flux measured
from T-0.20 sec in the 15-150 keV band is 1.3 +- 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/1216804/