TITLE:   GCN CIRCULAR
NUMBER:  31643
SUBJECT: ZTF22aabjpxh/AT2022cva (GRB 220219B): Mondy optical observations
DATE:    22/02/23 22:36:04 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

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

We observed ZTF22aabjpxh/AT2022cva discovered by ZTF (Ho et al., GCN 
31619) with AZT-33IK telescope of Mondy observatory on 2022-02-21  and 
2022-02-22. ZTF22aabjpxh/AT2022cva was observed also in optic (Kim  et 
al., GCN 31628; Hu et al., GCN 31639) and in X-ray by NICER (Pasham et 
al., GCN 31635). ZTF22aabjpxh/AT2022cva is considered the likely 
afterglow of GRB 220219B (Ho et al., GCN 31619; Svinkin et al., GCN 31624).

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 and preliminary 
photometry of a source (afterglow+host  galaxy) is following

Date       UT start  JD         Exp.    Filter  OT    Err.  UL(3sigma)
                     (mid, days)  (s)

2022-02-21 19:30:32  2.43966  30*120   R    19.19    0.03    22.8
2022-02-22 19:31:06  3.43936  29*120   R    19.34    0.03    22.8

The photometry is based on nearby SDSS DR12 stars
id                  r      R(Lupton) V(Lupton)
J160337.10+311328.5 16.987 16.79     17.19
J160343.10+311452.9 18.700 18.51     18.90

Assuming the host galaxy has R = 19.7 we subtract a host galaxy flux 
from a flux of the source (afterglow+host  galaxy) and estimated power 
law index of a light curve of the afterglow as -1.2,  which is typical 
for a GRB afterglow.