GCN Circular 23914
Subject
GRB 190220A: Swift-BAT refined analysis
Date
2019-02-20T17:59:59Z (5 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
K. L. Page (U Leicester), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 190220A (trigger #889785)
(Page et al., GCN Circ. 23908). The BAT ground-calculated position is
RA, Dec = 330.128, -76.669 deg which is
RA(J2000) = 22h 00m 30.7s
Dec(J2000) = -76d 40' 10.1"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 46%.
The mask-weighted light curve shows a single-pulse structure that starts
at ~T0, peaks at ~T+2 s, and ends at ~T+12 s. T90 (15-350 keV)
is 10.0 +- 2.0 sec (estimated error including systematics).
The time-averaged spectrum from T-0.12 to T+11.88 sec is best fit by a power law
with an exponential cutoff. This fit gives a photon index 0.79 +- 0.77,
and Epeak of 40.3 +- 6.7 keV (chi squared 60.03 for 56 d.o.f.). For this
model the total fluence in the 15-150 keV band is 8.9 +- 1.0 x 10^-7 erg/cm2
and the 1-sec peak flux measured from T+1.88 sec in the 15-150 keV band is
2.6 +- 0.4 ph/cm2/sec. A fit to a simple power law gives a photon index
of 2.03 +- 0.13 (chi squared 70.39 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/889785/BA/