SGR Swift J1818.0-1607: Swift-BAT refined analysis
Abstract
Using the data set from T-61 to T+242 sec from the recent telemetry downlink, we report further analysis of the BAT detection of a burst from a newly discovered SGR Swift J1818.0-1607 (trigger #960986) (Evans, et al., GCN Circ. 27373). The BAT ground-calculated position is RA, Dec = 274.515, -16.125 deg which is RA(J2000) = 18h 18m 03.7s Dec(J2000) = -16d 07' 31.8" with an uncertainty of 2.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 99%. The mask-weighted light curve in 2 ms time bins shows a burst that starts at T-0.005 sec, peaks at T+0.002 sec and ends at T+0.015 sec. There is a hint of a second pulse around T+0.01 s. T90 (15-350 keV) is ~0.01 sec. The time-averaged spectrum from T+0.00 to T+0.01 sec fit by a simple power-law model shows the power law index of 3.17 +- 0.63 (chi squared 51.9 for 57 d.o.f.). The fluence in the 15-150 keV band is 2.9 +- 1.1 x 10^-9 erg/cm2. The 1-sec peak photon flux measured from T+0.00 sec in the 15-150 keV band is 8.7 +- 3.1 ph/cm2/sec. A single blackbody fit to the time-averaged spectrum shows the blackbody temperature of 5.5 +- 0.9 keV (chi squared 43.2 for 57 d.o.f.). A thermal bremsstrahlung model fit shows the temperature of 15.8 +- 6.5 keV (chi squared 48.7 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/960986/BA/
- Publication:
-
GRB Coordinates Network
- Pub Date:
- March 2020
- Bibcode:
- 2020GCN.27384....1S