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GCN Circular 15589

Subject
Konus-Wind observation of GRB 131209A
Date
2013-12-10T13:08:14Z (10 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin,
P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf
of the Konus-Wind team, report:

The long-duration GRB 131209A
(Fermi LAT detection: Vianello & Omodei, GCN 15587;
IPN triangulation: Hurley at al., GCN 15588)
triggered Konus-Wind at T0=47280.491 s UT (13:08:00.491).

The burst light curve shows a broad pulse from ~T0-3 s to ~T0+17 s.
The emission is seen up to ~10 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB131209_T47280/

As observed by Konus-Wind, the burst
had a fluence of (1.4 � 0.1)x10-5 erg/cm2,
and a 64-ms peak flux, measured from T0+7.744 s,
of (3.2 � 0.3)x10-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+16.640 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.49 � 0.19,
the high energy photon index beta = -2.68 � 0.46,
the peak energy Ep = 235 � 29 keV,
chi2 = 91.2/97 dof.

The spectrum near the maximum count rate
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.17 � 0.17,
the high energy photon index beta = -2.49 � 0.22,
the peak energy Ep = 246 � 18 keV,
chi2 = 87.2/97 dof.

All the quoted values are preliminary.
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