TITLE:   GCN CIRCULAR
NUMBER:  39721
SUBJECT: Konus-Wind detection of GRB 250313A
DATE:    25/03/14 16:07:45 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 GRB 250313A (Fermi-GBM detection: Fermi GBM team, GCN 39703;
BALROG localization: Preis & Greiner, GCN 39704;
Fermi-LAT detection: Di Lalla et al., GCN 39711;
AstroSat CZTI detection: Dasgupta et al., GCN 39714;
SVOM/GRM observation: Wang et al., GCN 39716)
triggered Konus-Wind (KW) at T0=52473.618 s UT (14:34:33.618).

The burst light curve shows a bright, multi-peaked emission pulse,
with the duration of ~15 s, followed by a broad, weaker pulse,
peaked at T0+270 s. The total duration of the burst is ~345 s.
The emission is seen up to ~1.5 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB250313_T52473/

As observed by Konus-Wind, the burst had
a fluence of (1.06 ± 0.19)x10^-4 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 7.936 s,
of (1.23 ± 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+345 s)
is best fit in the 20 keV - 1.5 MeV range
by a GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.13 (-0.04,+0.04),
the high energy photon index beta = -2.64 (-0.73,+0.21),
the peak energy Ep = 237 (-15,+18) keV,
chi2 = 34/63 dof.

The spectrum near the peak count rate (measured from T0+7.936 s to T0+8.960 s)
is best fit in the 20 keV - 1.5 MeV range
by a GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.52 (-0.07,+0.08),
the high energy photon index beta = -2.80 (-0.41,+0.25),
the peak energy Ep = 294 (-20,+21) keV,
chi2 = 34/51 dof.

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