GCN Circular 31646
Subject
Konus-Wind observation of GRB 220219B
Event
Date
2022-02-25T05:54:26Z (4 years ago)
From
Anastasia Tsvetkova at Ioffe Institute <tsvetkova@mail.ioffe.ru>
A. Tsvetkova, D. Frederiks, A. Lysenko, A. Ridnaia, D. Svinkin,
M. Ulanov, and T. Cline on behalf of the Konus-Wind team, report:
The long-duration GRB 220219B
(IPN triangulation: Svinkin et al., GCN 31624),
consistent with the optical transient ZTF22aabjpxh/AT2022cva
reported by ZTF (Ho et al., GCN 31619),
triggered Konus-Wind at T0=34045.350 s UT (09:27:25.350).
The burst light curve consists of two broad pulses:
the first one lasts from ~T0-34 s to ~T0+13 s peaking at ~T0,
the second pulse lasts from ~T0+18 s to ~T0+45 s peaking at ~T0+20 s,
The emission is seen up to ~1 MeV.
As observed by Konus-Wind, the burst had
a fluence of the first pulse 1.21(-0.15,+0.16)x10^-5 erg/cm^2,
a fluence of the whole burst 1.76(-0.14,+0.12)x10^-5 erg/cm^2,
and a 64-ms peak energy flux, measured from T0-0.064 s,
of 1.76(-0.27,+0.52)x10^-6 erg/cm^2/s
(all in the 20 keV - 10 MeV energy range).
Since the main fraction of the first pulse was detected
before the trigger, its spectral analysis was performed using
the KW 3-channel light curve data.
Modelling its spectrum (measured from T0-33.723 s to T0+13.380 s)
by the exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep),
yields alpha = -1.86(-0.09,+4.36) and Ep = 39(-24,+27) keV.
Fitting the most intense part of the first pulse
(measured from T0-1.340 s to T0+1.604 s)
with by the exponential cutoff model yields
alpha = -1.75(-0.20,+4.25) and Ep = 61(-46,+24) keV.
The spectrum of the second emission pulse
(from T0+16.640 s to T0+49.408 s)
is well described by a simple power law (PL) with the photon PL index
of 2.60(-0.10,+0.10) and chi2/dof = 69.5/61.
Assuming the redshift z = 0.293 (Fremling et al., GCN 31629)
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 following burst rest-frame parameters:
the isotropic energy release in the first pulse is
Eiso = 2.75(-0.34,+0.36)x10^51 erg,
the isotropic peak luminosity is Liso = 5.17(-0.79,+1.53)x10^50 erg/s;
the rest-frame peak energy of the first pulse is Epiz = 50(-31,+35) keV;
and the rest-frame peak energy of the 'peak' spectrum is
Eppz = 79(-59,+31) keV.
With these values, GRB 220219B is within 68% prediction bands for
for both 'Amati' and 'Yonetoku' relations 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/GRB220219_T34045/GRB220219B_rest_frame.pdf
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB220219_T34045/
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.