TITLE:   GCN CIRCULAR
NUMBER:  31567
SUBJECT: GRB 210919A: Maidanak optical observations
DATE:    22/02/10 18:18:46 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

N. Pankov (HSE, IKI), A. Pozanenko (IKI), S. Belkin (IKI, HSE), O. 
Burhonov (UBAI),  Sh. Ehgamberdiev (UBAI) report on behalf of GRB IKI FuN:

We observed the filed of GRB 210919A detected by Swift (Tohuvavohu et 
al. GCN 30846) with AZT-22 1.5m telescope of Maidanak observatory on 
Sep. 19, and 20, 2021. Within enhanced Swift-XRT position (Goad et al. 
GNC 30850) we do not detect the potential afterglow (Kann et al. GCN 
30883, 30884) in both epochs. In the deep observation on 2021-09-19 with 
a mean seeing of 1" we  marginally detected the host galaxy candidate 
reported by O'Connor et al. (GCN 30934) and Kann et al. (GCN 30983) at 
the redshift of z=0.2411 (Rossi et al. GCN 31453). Using aperture 
photometry we found R = 24.05 +/- 0.35 of the host galaxy candidate. We 
do not detect the source at the eastern edge of the XRT error circle 
reported by  Kann et al. (GCN 30983).

Preliminary photometry of the field in following

Date       UT start  t-T0      Filter Exp.   OT  Err.  UL(3sigma)
                      (mid, days)        (s)
2021-09-19 22:27:50   0.94950    R    32*180 n/d n/d 24.2
2021-09-20 23:04:55   1.95651    R    14*180 n/d n/d 22.9

The photometry is based on the nearby SDSS-DR12 stars, R magnitude 
calculated by Lupton' transformations.