Swift J0840.7-3516 (AKA GRB 200205A): Swift-BAT refined analysis
Abstract
Using the data set from T-239 to T+255 sec from the recent telemetry downlink, we report further analysis of BAT source Swift J0840.7-3516 (trigger #954304) (Evans et al., GCN Circ. 26982). The BAT ground-calculated position is RA, Dec = 130.168, -35.275 deg which is RA(J2000) = 08h 40m 40.4s Dec(J2000) = -35d 16' 30.9" with an uncertainty of 3.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 94%. The mask weighted light curve shows some weak emission which started before the source came into BAT field of view (which is ~ T-100 sec). Kennea et al. 2020 (Atel #13452) discuss the properties of this newly discovered X-ray transient. The lower limit of the duration of the burst as detected by BAT is ~ 200 sec. The source went out of BAT field of view at ~T+260 sec, with a possibility of continuing emission which may be detected by other telecopes. The time-averaged spectrum from -81.88 to 132.86 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.84 +- 0.91, and Epeak of 31.5 +- 8.4 keV (chi squared 67.17 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is (1.3 +- 0.1) x 10^-06 erg/cm2 and the 1-sec peak flux measured from T-81.90 sec in the 15-150 keV band is 0.3 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 2.26 +- 0.17 (chi squared 77.17 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/954304/BA/
- Publication:
-
GRB Coordinates Network
- Pub Date:
- February 2020
- Bibcode:
- 2020GCN.27010....1S