TITLE: GCN CIRCULAR NUMBER: 35761 SUBJECT: GRB 240218A: Swift-BAT refined analysis DATE: 24/02/20 16:00:46 GMT FROM: Tyler Parsotan at NASA GSFC <tyler.parsotan@nasa.gov> 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), 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+200 sec from the recent telemetry downlink, we report further analysis of BAT GRB 240218A (trigger #1215912) (Page, et al., GCN Circ. 35742). The BAT ground-calculated position is RA, Dec = 161.810, 1.295 deg which is RA(J2000) = 10h 47m 14.4s Dec(J2000) = +01d 17' 40.2" with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 36%. The mask weighted light curve shows two major pulses, one that is broad and the other which is narrow. T90 (15-350 keV) is 66.93 +- 11.28 sec (estimated error including systematics). The time-averaged spectrum from T-38.93 to T+63.55 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.00 +- 0.32, and Epeak of 103.1 +- 45.5 keV (chi squared 62.59 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 5.2 +- 0.3 x 10^-06 erg/cm2 and the 1-sec peak flux measured from T+21.62 sec in the 15-150 keV band is 3.0 +- 0.3 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.51 +- 0.07 (chi squared 71.30 for 57 d.o.f.). 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/1215912/ View this GCN Circular online at https://gcn.nasa.gov/circulars/35761. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...