TITLE:   GCN CIRCULAR
NUMBER:  27849
SUBJECT: GRB 200528A: Assy optical upper limit
DATE:    20/05/29 08:09:05 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI), V. Kim (AFIF, Pulkovo Observatory), A. Pozanenko (IKI), 
M. Krugov (AFIF),  E. Mazaeva  (IKI),  A. Volnova (IKI)  report on 
behalf of larger GRB IKI FuN collaboration:

We observed  GRB 200528A (Fermi GBM Team  GCN 27831;   Ambrosi  et al., 
GCN 27832) with AZT-20 1.5 m telescope  of Assy-Turgen observatory 
starting on May., 28 (UT) 16:16:12.
We do not detect any sources in the Swift-XRT extended position (Evans 
et al., GCN 27836).

Preliminary photometry of the field is following.

Date       UT start   t-T0       Filter Exp.   OT   Err.   UL (3sigma)
                       (mid, days)        (s)

2020-05-28 16:16:12   0.26777    r(AB)  54*60  n/d  n/d    22.4

The photometry is based on the nearby stars of SDSS catalog

SDSS-DR12_id        r
J114613.33+581329.5 19.455
J114632.90+581307.2 19.190
J114549.81+581044.3 19.004
J114600.53+580839.6 16.985