GCN Circular 44167
Subject
Konus-Wind detection of GRB 260320A
Event
Date
2026-03-31T13:34:05Z (6 months ago)
From
Valentina Panteleeva at Ioffe Institute <panteleevav228@gmail.com>
Via
Web form
V. Panteleeva, 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 260320A
(NuSTAR detection: Waratkar et al., GCN 44064,
Insight-HXMT/HE detection: Luo et al., GCN 44077,
Glowbug gamma-ray detection: Cheung et al., GCN 44093,
GRID detection: Li et al., GCN 44109,
IPN triangulation: Kozyrev et al., GCN 44121)
triggered Konus-Wind at T0=70801.257 s UT (19:40:01.257).
The burst light curve shows a single pulse
which starts at ~T0-0.4 s and has a total duration of ~13.1 s.
The emission is seen up to ~1 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB260320_T70801/
As observed by Konus-Wind, the burst
had the total fluence of 1.88(-0.20,+0.19)x10^-5 erg/cm2,
and the 64-ms peak flux, measured from T0+0.896 s,
of 6.92(-0.78,+0.80)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 the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.18(-0.10,+0.10),
the high energy photon index beta = -2.44(-0.43,+0.18),
the peak energy Ep = 267(-32,+45) keV
(chi2 = 86/91 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 = -1.33(-0.06,+0.06)
and Ep = 359(-36,+44) keV (chi2 = 82/77 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.29
(chi2 = 82/76 dof).
All the quoted errors are at the 68% confidence level.
All the quoted values are preliminary.