GCN Circular 35622

T. Parsotan (GSFC), S. D. Barthelmy (GSFC),
A. D'Ai (INAF-IASFPA), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa),
C. B. Markwardt (GSFC), M. J. Moss (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU) (i.e. the Swift-BAT team):

Using the data set from T-240 to T+820 sec from the recent telemetry
downlink,
we report further analysis of BAT GRB 240123A (trigger #1210276)
(D'Ai, et al., GCN Circ. 35602
Not found
 
 
).  The BAT ground-calculated position is
RA, Dec = 199.287, 60.607 deg which is
   RA(J2000)  =  13h 17m 08.9s
   Dec(J2000) = +60d 36' 25.6"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 31%.

The mask-weighted light curve shows some weak emission with complex
structures
that starts at ~T0 and ends at ~T+140 s. The main peak occurs at ~T+5 s.
T90 (15-350 keV) is 115.30 +- 54.93 sec (estimated error including
systematics).

The time-averaged spectrum from T-0.69 to T+140.46 sec is best fit by a
simple
power-law model.  The power law index of the time-averaged spectrum is
1.69 +- 0.23.  The fluence in the 15-150 keV band is 1.6 +- 0.2 x 10^-6
erg/cm2.
The 1-sec peak photon flux measured from T+5.49 sec in the 15-150 keV band
is 1.1 +- 0.3 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1210276/BA/