GRB 241127A: Swift-BAT refined analysis

Using the data set from T-50 to T+242 sec from the recent telemetry downlink, we report further analysis of BAT GRB 241127A (trigger #1270788) (Salvaggio et al., GCN Circ. 38354). The BAT ground-calculated position is RA, Dec = 327.911, -56.652 deg which is RA(J2000) = 21h 51m 38.5s Dec(J2000) = -56d 39' 08.1" with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows some weak emission that starts at ~T-21 s, followed by the main pulse that starts at ~T-1 s, peaks at ~T+1 s, and ends at ~T+9 s. T90 (15-350 keV) is 26.02 +- 3.63 sec (estimated error including systematics). The time-averaged spectrum from T-20.83 to T+9.13 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.10 +- 1.01, and Epeak of 19.0 +- 12.56 keV (chi squared 52.96 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 6.5 +- 0.8 x 10^-07 erg/cm2 and the 1-sec peak flux measured from T+0.09 sec in the 15-150 keV band is 2.3 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 2.65 +- 0.21 (chi squared 60.15 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/1270788