GCN Circular 39149
Subject
Konus-Wind detection of GRB 250202B
Date
2025-02-05T13:40:11Z (5 days ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
Via
email
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 GRB 250202B (Fermi-GBM detection: The Fermi GBM team, GCN 39120;
Bala et al., GCN 39133; AstroSat-CZTI detection: Srijan et al., GCN 39122;
NuSTAR-ACS detection: Grefenstette, GCN 39135; IPN triangulation: Svinkin et al., GCN 39144)
triggered Konus-Wind (KW) at T0=14235.288 s UT (03:57:15.288).
The burst light curve consists of multiple multi-peaked emission pulses.
The total duration of the burst is ~100 s.
The emission is seen up to ~10 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB250202_T14235/
As observed by Konus-Wind, the burst had
a fluence of (2.05 ± 0.07)x10^-4 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 2.112 s,
of (1.62 ± 0.10)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+106.240 s)
is best fit in the 20 keV - 15 MeV range
by a GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.87 (-0.05,+0.06),
the high energy photon index beta = -2.67 (-0.12,+0.09),
the peak energy Ep = 273 (-8,+9) keV,
chi2 = 121/97 dof.
The spectrum near the peak count rate (measured from T0 to T0+2.560 s)
is best fit in the 20 keV - 15 MeV range
by a GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.38 (-0.07,+0.08),
the high energy photon index beta = -3.40 (-0.72,+0.33),
the peak energy Ep = 413 (-21,+21) keV,
chi2 = 63/60 dof.
All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.