TITLE: GCN CIRCULAR NUMBER: 12707 SUBJECT: GRB 110820A: optical observations in Maidanak observatory DATE: 11/12/20 12:49:33 GMT FROM: Alina Volnova at SAI MSU A. Volnova (SAI MSU), M. Ibrahimov (UBAI), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift GRB 110820A (Troja et al., GCN 12288) with AZT-22 telescope of Maidanak observatory on Aug. 20 starting on 21:54:54 UT in R band. We took 6 frames with exposure of 300 seconds under good weather condition and seeing (FWHM) of about 0.7". On the stacked image we do not detect the source reported by Im et al. (GCNs 12295, 12297). The photometry is based on the USNO B1.0 star USNO-B1.0 1603-0160240, (J2000) RA = 22:52:56.89 Dec = +70:18:37.5, assuming R =17.19: Tstart UT, T0+, Filter, Exposure, OT, Upper Limit (3 sigma) (mid, d) (s) 21:54:54 0.18924 R 6*300 n/d 22.5