GCN Circular 33579
Subject
GRB 230307A: further analysis of the Konus-Wind detection and rest-frame energetics
Event
Date
2023-04-06T16:11:37Z (3 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
D. Svinkin, D. Frederiks, A. Ridnaia, A. Tsvetkova,
and A. Lysenko on behalf of the Konus-Wind team, report:
Following the probable host galaxy identification
(Gillanders et al. GCN Circ. 33485; Levan at al., GCN Circ. 33569),
we present a further analysis of the KW detection
(Svinkin et al., GCN Circ. 33427)
of the extremely bright, long-duration GRB 230307A
(GCNs 33405, 33406, 33407, 33410, 33411, 33412,
33413, 33414, 33415, 33416, 33418, 33424, 33425, 33461).
As measured by KW the burst durations are
T50=9.17+/-0.04 s and T90 = 31.2 +/-0.4 s,
both in the 100-1700 keV energy band.
The refined burst fluence is 4.05(-0.03,+0.03)x10^-3 erg/cm2,
and a 64-ms peak flux, measured from T0+6.224 s,
is 6.85(-0.27,+0.27)x10^-4 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
Assuming the redshift of the host galaxy z=0.065 (GCN 33485)
and a standard cosmology model with H_0 = 67.3 km/s/Mpc,
Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is (4.21+/-0.03)x10^52 erg,
the peak luminosity L_iso is (7.58 +/-0.33)x10^51 erg/s,
the rest-frame peak energy of the time-integrated spectrum,
Ep,i,z is (933+/-12) keV, and the rest-frame peak energy at the peak
luminosity Ep,p,z is (1388+/-52) keV.
With these values, GRB 230307A is outside the 90% prediction band of
both 'Amati' and 'Yonetoku' relations built for the sample of >300 long
KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al.,
2021).
In both Eiso-Ep,i,z and Liso-Ep,p,z planes, GRB 230307A is shifted
towards the short-hard (Type I, merger-origin) GRB population,
see http://www.ioffe.ru/LEA/GRBs/GRB230307_T56645/GRB230307A_rest_frame.pdf
The analysis of KW data is ongoing and its results will be reported
elsewhere.