GRB 220521A: Swift-BAT refined analysis

Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 220521A (trigger #1107466) (Dichiara et al., GCN Circ. 32076). The BAT ground-calculated position is RA, Dec = 275.218, 10.372 deg which is RA(J2000) = 18h 20m 52.3s Dec(J2000) = +10d 22' 20.0" with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 46%. The mask-weighted light curve shows a multi-peaked structure that starts at ~T0 and ends at ~T+16 s. The two main peaks occur at ~T+0.5 s and ~T+10 s, respectively. T90 (15-350 keV) is 13.55 +- 2.69 sec (estimated error including systematics). The time-averaged spectrum from T-0.23 to T+16.17 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.97 +- 0.18. The fluence in the 15-150 keV band is 8.1 +- 0.8 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.18 sec in the 15-150 keV band is 4.7 +- 0.4 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/1107466/BA/