TITLE:   GCN CIRCULAR
NUMBER:  36254
SUBJECT: GRB 240418A: Swift-BAT refined analysis
DATE:    24/04/23 12:59:27 GMT
FROM:    Mike Moss at NASA GSFC <mikejmoss3@gmail.com>

D. M. Palmer (LANL), S. D. Barthelmy (GSFC),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
M. J. Moss (GSFC), T. Parsotan (GSFC),
T. Sakamoto (AGU), M. H. Siegel (PSU)
(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 240418A (trigger #1222885)
(Siegel, et al., GCN Circ. 36162).  The BAT ground-calculated position is
RA, Dec = 239.342, 23.632 deg which is
   RA(J2000)  =  15h 57m 22.0s
   Dec(J2000) = +23d 37' 54.4"
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 79%.
 
The mask-weighted light curve shows a single, dim pulse peaking at T0+5 s.
The T90 (15-350 keV) is 12.00 +- 3.61 sec (estimated error including systematics).
 
The time-averaged spectrum from T-0.47 to T+12.53 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.99 +- 0.31.  The fluence in the 15-150 keV band is 2.3 +- 0.5 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T+4.53 sec in the 15-150 keV band
is 0.5 +- 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/1222885