GRB 220219B

D. Svinkin, D. Frederiks, A. Ridnaia, A. Lysenko,
and T. Cline on behalf of the Konus-Wind team, and

S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT team, report:

The long-duration GRB 220219B
has been detected by Konus-Wind (KW) and Swift (BAT), so far,
at about 34045 s UT (09:27:25).
The burst was outside the coded field of view of the BAT.

We have triangulated it to a Konus-BAT annulus centered at
RA(2000)=314.433 deg (20h 57m 44s) Dec(2000)=-14.987 deg (-14d 59' 15"),
whose radius is 83.789 +/- 1.439 deg (3 sigma).

This localization may be improved.

The position of the optical transient ZTF22aabjpxh/AT2022cva
Loading...
 
 
(Ho et al., GCN Circ. 31619
Loading...
 
 ) is inside the annulus at 0.46 deg
from its center line. The OT position is consistent with the Swift-BAT 
detection, Fermi-GBM non-detection, and the KW ecliptic latitude response.

The positional and temporal coincidence of this burst with the OT 
supports the conclusion that the OT is the GRB counterpart.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB220219_T34045/IPN

The time history and spectrum will be given in forthcoming GCN Circulars.

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a ToO observation of the Konus-Wind GRB 220219B. 
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021481

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Konus-Wind event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a 
GCN Circular after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.

A.P. Beardmore (U. Leicester), M. Capalbi (INAF-IASFPA), M. Perri (SSDC
& INAF-OAR), V. D'Elia (SSDC & INAF-OAR), D.N. Burrows (PSU), J. D.
Gropp (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester) and P.A.
Evans (U. Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of GRB 220219B (Svinkin
et al., GCN Circ. 31624
Loading...
 
 ), collecting 3.5 ks of Photon Counting (PC)
mode data between T0+322.5 ks and T0+369.3 ks. 

One uncatalogued X-ray source has been detected at a position
consistent with the GRB optical afterglow candidate
ZTF22aabjpxh/AT2022cva
Loading...
 
  (Ho et al., GCN Circ. 31619
Loading...
 
 ). The X-ray source 
is below the RASS limit and shows no definitive signs of fading.
Details of this source are given below:

Source 1:
  RA (J2000.0):  240.91414  =  16:03:39.39
  Dec (J2000.0): +31.23404  =  +31:14:02.5
  Error: 2.8 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: 0.0250 [+0.0032, -0.0031] ct s^-1   
  Flux: (1.06 [+0.14, -0.13])e-12 erg cm^-2 s^-1 (observed, 0.3-10 keV)


The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
https://www.swift.ac.uk/ToO_GRBs/00021481.

This circular is an official product of the Swift-XRT team.

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
Loading...
 
 ),
consistent with the optical transient ZTF22aabjpxh/AT2022cva
Loading...
 
 
reported by ZTF (Ho et al., GCN 31619
Loading...
 
 ),
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
Loading...
 
 )
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.