TITLE:   GCN CIRCULAR
NUMBER:  26818
SUBJECT: GRB 200115A: Mondy optical observations and correction to GCN 26790
DATE:    20/01/19 17:33:26 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

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

We observed the field of  GRB 200115A (Cenko et al.,  GCN 26771) with 
AZT-33IK telescope of Sayan observatory (Mondy) starting on Jan. 16 (UT) 
  12:30:28. Within  BAT ground-calculated position (Laha et al. GCN 
26780) we  do not detect any  unidentified objects in comparison with 
SDSS-DR2. We also not detected the afterglow candidate reported after 
our first epoch observation (Pozanenko et al., GCN 26790).

We report the correction of R-magnitude of the afterglow candidate.
The result presented below overrides previously reported (GCN 26790) 
R-magnitude. We apologize for the typo and possible inconvenience.

Due to shallow upper limit in the second epoch observation  we cannot 
confirm variability of the afterglow candidate.

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

2020-01-15 11:55:00   0.02455    R      30*120  21.9  0.2   22.1
2020-01-16 12:30:28   1.05039    R      32*120  n/d   n/d   21.6

The photometry is based on the nearby SDSS DR12 stars
SDSS                 R_Lupton
J034551.63+053704.5  17.138  0.016
J034547.51+053555.6  18.214  0.029
J034543.70+053549.4  17.851  0.022