TITLE:   GCN CIRCULAR
NUMBER:  45925
SUBJECT: Konus-Wind detection of GRB 261010A
DATE:    26/10/12 16:48:04 GMT
FROM:    Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>

D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin,
A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The long-duration GRB 261010A (Swift detection:
Lien, et al., GCN 45889; Barthelmy et al., GCN 45918;
Fermi-GBM detection: The Fermi GBM team, GCN 45888;
Palafox & Jameson, GCN 45911)
triggered Konus-Wind (KW) at T0=69424.522 s UT (19:17:04.522).

The KW triggered on a bright, hard-spectrum, multipeaked pulse,
with a duration of ~3 s, which is superimposed over a broad,
less intense emission pulse that started ~10 s before the trigger,
peaked at ~T0+16 s, and lasted for ~70 s.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB261010_T69424/

As observed by Konus-Wind, the burst had
a fluence of (1.72 ± 0.47)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 0.128 s,
of (6.02 ± 1.08)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

The spectrum of the bright pulse (measured from T0 to T0+8.448 s)
is best fitted in the 20 keV - 15 MeV range by a power law with exponential
cutoff (CPL) model dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.98 (-0.12, + 0.15) and Ep = 837(-194,+299) keV, PGstat = 81/98 dof.
Fitting this spectrum by a Band GRB function yields the same values
of alpha and Ep, and only an upper limit on the high energy photon
index beta of -2.0

The spectrum of the broad pulse (measured from T0+8.448 s to T0+49.408 s)
is best fitted in the 20 keV - 15 MeV range by a simple PL function
with the PL index of 1.92 (-0.07,+0.08),
PGstat = 103/99 dof.

All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.