TITLE:   GCN CIRCULAR
NUMBER:  31683
SUBJECT: ZTF22aabjpxh/AT2022cva (GRB 220219B): continued optical observations, SN signature search
DATE:    22/03/05 10:45:37 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI, HSE), A. Pozanenko (IKI), N. Pankov (HSE), E. Klunko 
(ISTP), I. Reva (FAI), V. Kim (FAI) report  on behalf of GRB IKI FuN:

We are continuing observations of ZTF22aabjpxh/AT2022cva discovered by 
ZTF (Ho et al., GCN 31619) with AZT-33IK telescope of Mondy observatory 
and Zeiss-1000 on 2022-02-21 between 2022-02-23 and 2022-03-04, i.e. upt 
13.4 days after GRB 220219B trigger. ZTF22aabjpxh/AT2022cva was observed 
in optic (Kim  et al., GCN 31628; Hu et al., GCN 31639) and in X-ray by 
NICER (Pasham et al., GCN 31635) and XRT/Swift (Beardmore et al., GCN 
31644). ZTF22aabjpxh/AT2022cva is considered the likely afterglow of GRB 
220219B (Ho et al., GCN 31619; Svinkin et al., GCN 31624; Tsvetkova et 
al., GCN 31646).

We clearly detect  the SDSS galaxy at z=0.293 (Fremling et al., GCN 
31629). Due to non-optimal seeing we could not  discriminate the 
afterglow from the galaxy. We use aperture  photometry of a source 
(afterglow + host  galaxy). Based on our  preliminary photometry we plot 
  a light curve  of the source, see upper panel of the Figure in

http://grb.rssi.ru/GRB220219B/GRB220219B_AT2022cva_LC.png

To estimate power law index of the afterglow we fit our photometric data 
by a single power law + constant host galaxy flux. The host galaxy fit 
is R = 19.68+/-0.05 and PL index alpha = -1.75+/-0.4. The light curve of 
the afterglow after subtraction of a flux of the host is presented at 
bottom panel of the Figure in

http://grb.rssi.ru/GRB220219B/GRB220219B_AT2022cva_LC.png

Power Law index is broadly compatible with the index of -1.6 obtained in 
XRT observations up to ~8 days, see XRT light curve at

https://www.swift.ac.uk/xrt_live_cat/00021481/

We may conclude the source ZTF22aabjpxh/AT2022cva is the optical 
afterglow of GRB 220219B.

Since the redshift of GRB 220219B (ZTF22aabjpxh/AT2022cva) is z=0.293 
(Fremling et al., GCN 31629) we are searching for a supernova signature. 
  Based on the Figure referenced above we still don't see any conclusive 
evidence for the existence of SN.

We urge further multicolour observations to confirm/search for SN 
associated with GRB 220219B.