V. Kim (FAI, Pulkovo Observatory), N. Pankov (HSE, IKI), M. Krugov
(FAI), A. Pozanenko (IKI), S. Belkin (IKI) report on behalf of GRB IKI FuN:
We observed the field of ZTF21aayokph (AT2021lfa) (Yao et al., GCN
29938) with AZT-20 telescope of Assy-Turgen observatory starting on
2021-05-05 (UT) 15:51:00.
We clearly detect the optical transient (Yao et al., GCN 29938; Watson
et al., GCN 29940; Butler et al., GCN 29941; Yao et al., GCN 29945; Fu
et al., GCN 29948).
Preliminary photometry of the optical transient in r',i' - filters is
Date UT start t-T0 Exp. Filter OT Err. UL(3sigma)
(mid, days) (s)
2021-05-05 15:51:00 n/a 35*60 r' 21.20 0.06 22.5
2021-05-05 16:40:30 n/a 57*60 i' 20.83 0.06 21.8
The photometry is based on the nearby SDSS-DR12 stars.
We note the same color r'-i'= 0.37 +/- 0.08 of our observations and the
color which can be deduced from RATIR observations r-i = 0.42 +/- 0.07
at ~0.5 days earlier (Butler et al., GCN 29941).