GRB 220408A: Swift-BAT refined analysis
Abstract
Using the data set from T-119 to T+183 sec from the recent telemetry downlink, we report further analysis of BAT GRB 220408A (trigger #1101675) (Caputo, et al., GCN Circ. 31848). The BAT ground-calculated position is RA, Dec = 202.399, 47.065 deg which is RA(J2000) = 13h 29m 35.7s Dec(J2000) = +47d 03' 55.4" with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 34%. The mask-weighted light curve shows a multi-peaked structure that starts at T-2 s and peaks at T+3 s. There is a weak emission which peaks at T+17 s. T90 (15-350 keV) is 17.25 +- 1.10 sec (estimated error including systematics). The time-averaged spectrum from T-0.55 to T+18.26 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.19 +- 0.57, and Epeak of 35.3 +- 8.8 keV (chi squared 62.40 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+2.48 sec in the 15-150 keV band is 4.9 +- 0.4 ph/cm2/sec. A fit to a simple power law gives a photon index of 2.14 +- 0.13 (chi squared 72.77 for 57 d.o.f.). 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/1101675/BA/
- Publication:
-
GRB Coordinates Network
- Pub Date:
- April 2022
- Bibcode:
- 2022GCN.31874....1P