[vsnet-grb-info 27593] Konus-Wind detection of GRB 210321A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29696
SUBJECT: Konus-Wind detection of GRB 210321A
DATE:    21/03/23 12:37:30 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred at mail.ioffe.ru>

D. Frederiks, S. Golenetskii, A.Lysenko, D. Svinkin, A. Ridnaya,
A. Tsvetkova,  M. Ulanov, and T. Cline, report:

The long GRB 210321A (Swift-BAT trigger #1037828, T0(BAT)= 07:13:51.023 UT:
Dichiara, et al., GCN 29677; Ukwatta, et al., GCN 29691)
was detected by Konus-Wind (KW) in the waiting mode.

A Bayesian block analysis of the KW waiting mode data in the 20-400 keV band
reveals a ~10 sigma count rate increase over background in the interval
from ~T0(BAT)-6.430 s to ~T0(BAT)+2.402 s.

A fit to the KW 3-cannel waiting mode spectrum with by a power law with
an exponential cutoff (CPL) yields alpha~-2 and doesn't constrain Ep.
A fit with a simple power law (PL) gives a photon index of (2.19 ± 0.17), chi^2 = 0.78/ 1 dof.
This result is consistent with the Swift-BAT refined analysis (GCN 29691).

In the 10 keV-10 MeV band, standard for the KW spectral analysis, the total burst fluence,
estimated from the PL model, is (1.6 ± 0.3)x10^-6 erg/cm^2,
and the 2.944 s peak energy flux is (2.2 ± 0.4)x10^-7 erg/cm^2.

Assuming the redshift z=1.487 (de Ugarte Postigo, et al., GCN 29685)
and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315,
and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the burst isotropic energy release E_iso to ~9.7x10^51 erg
and the isotropic luminosity L_iso to ~3.2x10^51 erg/s.

The KW light curve of this burst is available
at http://www.ioffe.ru/LEA/GRBs/GRB210321A/