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GCN Circular 27012

Subject
GRB 200205B: Swift-BAT refined analysis
Date
2020-02-08T02:03:36Z (4 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), P. A. Evans (U Leicester),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU) (i.e. the Swift-BAT team):

Using the data set from T-239 to T+1361 sec from the recent telemetry
downlink,
we report further analysis of BAT GRB 200205B (trigger #954519 and #954520)
(Evans et al., GCN Circ. 26993). We have combined the data from two
triggers (#954519 and #954520) for the analysis. All the times in this
circular
are relative to the trigger time from #954519.

The BAT ground-calculated position is
RA, Dec = 107.760, -56.488 deg which is
   RA(J2000)  =  07h 11m 02.3s
   Dec(J2000) = -56d 29' 18.1"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 47%.

The mask-weighted light curve shows several pulses that start from
~T+20 s and end at ~T+550 s. The first prominent pulse occurs at ~T+60 s,
followed by another significant structure with several overlapping pulses
from ~T+380 s to ~T+520 s. There is a data gap from T+63 s to T+160 s,
likely due to problems of saving data because of the double triggers.
T90 (15-350 keV) is 458.0 +- 5.4 sec (estimated error including
systematics).

Because of the data gap for part of the first pulse, we performed
the time-averaged spectrum for the interval of the second multi-pulse
structure
from T+387.008 to T+520.396 sec. This interval is best fit by a power law
with
an exponential cutoff. This fit gives a photon index 1.36 +- 0.22,
and Epeak of 65.6 +- 10.8 keV (chi squared 41.92 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 5.4 +- 0.2 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+438 sec in the 15-150 keV band is
2.0 +- 0.2 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.84 +- 0.05 (chi squared 58.00 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/954519/BA/
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