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
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