GCN Circular 45496
Subject
Konus-Wind detection of GRB 260829A
Event
Date
2026-09-02T11:12:15Z (a day ago)
From
Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>
Via
Web form
A. Ridnaia, D. Frederiks, A. Lysenko, V. Panteleeva,
D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:
The long-duration GRB 260829A
(Fermi-GBM detection: Fermi GBM team, GCN 45464;
Malacaria et al., GCN 45467;
BALROG localization: Preis & Greiner, GCN 45465;
GECAM-B detection: Zao et al., GCN 45470;
IPN triangulation: Kozyrev et al., GCN 45476;
AstroSat CZTI detection: Goyal et al., GCN 45485;
SVOM-GRM detection: Luo et al., GCN 45495)
triggered Konus-Wind at T0=22110.076 s UT (06:08:30.076).
The burst light curve shows an initial weak emission
episode starting at ~T0-21.3 s, followed by a brighter
multi-peaked structure. The total burst duration is ~34.8 s.
The emission is seen up to ~4 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB260829_T22110/
As observed by Konus-Wind, the burst
had the total fluence of 2.05(-0.09,+0.10)x10^-5 erg/cm2,
and the 64-ms peak flux, measured from T0+2.208 s,
of 8.44(-0.91,+0.92)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst
(measured from T0 to T0+16.640 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.94(-0.09,+0.09)
and Ep = 330(-24,+28) keV (chi2 = 114/98 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.8
(chi2 = 114/97 dof).
The spectrum near the maximum count rate
(measured from T0+0.256 to T0+8.448 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.75(-0.08,+0.08)
and Ep = 314(-17,+19) keV (chi2 = 122/88 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -3.0
(chi2 = 122/87 dof).
All the quoted errors are at the 68% confidence level.
All the quoted values are preliminary.