[vsnet-grb-info 28094] Konus-Wind detection of GRB 210610A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30197
SUBJECT: Konus-Wind detection of GRB 210610A
DATE:    21/06/11 11:56:36 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 210610A (Swift-BAT detection: Page et al., GCN 30160; Barthelmy et al., GCN 30186),
T0 (BAT) = 15:03:43/387, 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 ~8 sigma count rate increase over background in the interval
from ~T0(BAT)-2 s to ~T0(BAT)+4 s.
The KW light curve of this burst is available
at http://www.ioffe.ru/LEA/GRBs/GRB210610A/

Modeling the KW 3-channel spectrum
by a power law with exponential cutoff (CPL) model
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -0.17(-0.83,+1.15) and Ep = 148(-63,+87) keV.

In the 10 keV -10 MeV band, the total burst fluence is (1.3 ± 0.5)x10^-6 erg/cm^2,
and the 2.944 s peak energy flux is (2.7 ± 0.8)x10^-7 erg/cm^2.

Assuming the redshift z=3.54 (Zhu et al., GCN 30164)
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 isotropic energy release E_iso to ~3.5x10^52 erg,
the isotropic luminosity L_iso to ~3.3x10^52 erg/s,
and the rest-frame peak energy of the time-integrated spectrum Ep,z to ~670 keV.
With these values, GRB 210610A is within 90% prediction bands for
for the 'Amati' relation for the sample of >300 long KW GRBs
with known redshifts (Tsvetkova et al., 2021, ApJ, 908, 83),
see http://www.ioffe.ru/LEA/GRBs/GRB210610A/GRB210610A_rest_frame.pdf

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