[vsnet-grb-info 7113] Konus-Wind observation of GRB 081221

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8694
SUBJECT: Konus-Wind observation of GRB 081221
DATE:    08/12/22 11:05:55 GMT
FROM:    Valentin Pal'shin at Ioffe Inst  <val at mail.ioffe.ru>

S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin,
D. Frederiks, P. Oleynik, D. Svinkin, M. Ulanov,
and T. Cline, on behalf of the Konus-Wind team report:

The long GRB 081221 (Hoversten et al., GCN 8687)
triggered Konus-Wind at T0=58874.915 s UT (16:21:14.915).

The burst light curve shows two multipeaked pulses with a total
duration of ~40 s.

As observed by Konus-Wind the burst
had a fluence of (2.28 +/- 0.07)x10^-5 erg/cm2,
and a 256-ms peak flux measured from T0+19.824 s
of (1.75 +/- 0.16)x10^-6 erg/cm2/s
(both in the 20 keV - 1 MeV energy range).

The time-integrated spectrum of the burst
(from T0 to T0+39.424 s) can be fitted (in the 20 keV-1 MeV range)
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.91(-0.14, +0.15),
and Ep = (83 +/- 4) keV (chi2 = 67.4/51 dof).
Fitting by GRB (Band) model yields the same alpha and Ep,
and only an upper limit on the high energy
photon index: beta < -3.48 (chi2 = 67.4/50 dof).

Thus, it is a bright and soft GRB.

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

The Konus-Wind light curve of this GRB is available
at http://www.ioffe.ru/LEA/GRBs/GRB081221_T58874/