[vsnet-grb-info 21396] Konus-Wind observation of GRB 181201A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23495
SUBJECT: Konus-Wind observation of GRB 181201A
DATE:    18/12/03 16:42:48 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin at mail.ioffe.ru>

D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks,
M. Ulanov, A. Tsvetkova, A. Lysenko, A. Kozlova, and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration GRB 181201A
(INTEGRAL-IBIS/ISGRI detection: Mereghetti et al., GCN Circ. 23469;
Insight-HXMT/HE detection: Cai et al., GCN Circ. 23491)
triggered Konus-Wind at T0=9592.355 s UT (02:39:52.355).

The burst light curve consists of two well-separated pulses
with the first pulse staring at ~T0-115 s,
and a total burst duration of ~172 s.
The emission is seen up to ~15 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB181201_T09592/

As observed by Konus-Wind, the burst
had a fluence of 1.99(-0.06,+0.06)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+4.848 s,
of 2.88(-0.33,+0.34)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+34.816 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.25(-0.05,+0.05),
the high energy photon index beta = -2.73(-0.12,+0.11),
the peak energy Ep = 152(-6,+6) keV
(chi2 = 114/97 dof).

The spectrum near the maximum count rate
(measured from T0+4.352 to T0+4.864 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.75(-0.16,+0.19),
the high energy photon index beta = -2.76(-0.38,+0.21),
the peak energy Ep = 207(-24,+26) keV
(chi2 = 51/49 dof).

Assuming the redshift z=0.450 (Izzo et al., GCN Circ. 23488)
and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.27, and Omega_Lambda = 0.73,
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~1.0x10^53 erg,
the peak luminosity L_iso is ~2.2x10^52 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,i, is ~220 keV.

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.