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GCN Circular 27148

Subject
GRB 200219A, Swift-BAT refined analysis
Date
2020-02-20T04:14:14Z (4 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
J. P. Norris (BSU), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-240 to T+962 sec from the recent telemetry
downlink,
we report further analysis of BAT GRB 200219A (trigger #957271)
(Lien et al., GCN Circ. 27125).  The BAT ground-calculated position is
RA, Dec = 342.595, -59.101 deg which is
   RA(J2000)  =  22h 50m 22.7s
   Dec(J2000) = -59d 06' 04.5"
with an uncertainty of 2.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 99%.

The mask-weighted light curve shows a short pulse that starts and peaks at
~T0,
and ends at ~T+0.5 s. It is followed by an extended emission that lasting
until ~T+90 s. In addition, there may be some even weaker emission until
~T+300 s.
T90 (15-350 keV) is 288.0 +- 50.6 sec (estimated error including
systematics).

The time-averaged spectrum from T-0.2 to T+86.7 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.47 +- 0.25.  The fluence in the 15-150 keV band is 7.4 +- 1.1 x 10^-7
erg/cm2.
The 1-sec peak photon flux measured from T-0.268 sec in the 15-150 keV band
is 2.4 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

Because the burst seems to be similar to short GRBs with extended emission,
we perform further spectral analysis for the short pulse and the extended
emission. The short pulse from T-0.224 s to T+0.496 s (determined by the
Bayesian block analysis) is best fit by a simple power-law model.
The power law index of the time-averaged spectrum is 0.69 +- 0.14. The
fluence in the 15-150 keV band is 2.5 +- 0.2 x 10^-7 erg/cm2.
The extended emission from T+0.496 s to T+86.704 s is best fit by a
simple power-law model. The power law index of the time-averaged
spectrum is 1.78 +- 0.33.  The fluence in the 15-150 keV band is
4.9 +- 1.0 x 10^-7 erg/cm2.

The spectral lag of the short pulse is 14 (+5, -5) ms for the 100-350 keV
to 25-50 keV bands, and 20 (+15, -10) ms for the 50-100 keV to 15-25 keV
bands. These values are more consistent with those of long GRBs.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/957271/BA/
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