TITLE:   GCN CIRCULAR
NUMBER:  30388
SUBJECT: Konus-Wind detection of GRB 210704A
DATE:    21/07/06 09:51:51 GMT
FROM:    Anna Ridnaia at Ioffe Institute  <ridnaia@mail.ioffe.ru>

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

The long-duration GRB 210704A
(BALROG localization: Kunzweiler et al., GCN 30369;
AGILE/MCAL detection: Ursi et al., GCN 30372;
Fermi-LAT detection: Berretta et al., GCN 30375;
AstroSat CZTI detection: Prasad et al., GCN 30378;
Fermi GBM detection: Malacaria & Meegan, GCN 30380)
triggered Konus-Wind at T0=70400.814 s UT (19:33:20.814).

The burst light curve shows a bright peak
in the interval from ~T0 to ~T0+2 s followed by
a weaker pulse peaked at ~T0+4.5 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/GRB210704_T70400/

As observed by Konus-Wind, the burst
had a fluence of 2.25(-0.12,+0.14)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+0.528 s,
of 3.31(-0.37,+0.39)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+1.536 s)
is best fit in the 20 keV - 4 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.21(-0.09,+0.10),
the high energy photon index beta = -2.97(-0.31,+0.22),
the peak energy Ep = 271(-14,+14) keV
(chi2 = 56/57 dof).

The spectrum near the maximum count rate
(measured from T0+0.256 to T0+0.768 s)
is best fit in the 20 keV - 4 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.20(-0.12,+0.13),
the high energy photon index beta = -2.84(-0.40,+0.25),
the peak energy Ep = 320(-24,+27) keV
(chi2 = 44/53 dof).

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.