GRB 201001A: TSHAO optical upper limit

We observed the field of GRB 201001A (Simpson et al., GCN 28539) with Zeiss-1000 1-m telescope of Tien Shan Astronomical Observatory starting on Oct. 01 (UT) 22:56:08. No optical source is detected within enhanced Swift-XRT position (Evans et al., GCN 28540). This corresponds to the absence of the source in earlier optical observations (Simpson et al., GCN 28539; Hosokawa et al., GCN 28548; Fu et al., GCN 28549). Preliminary photometry of the field is following. Date UT start t-T0 Filter Exp. OT Err. UL(3 sigma) (mid, days) (s) 2020-10-01 22:56:08 0.54732 R 22*50 n/d n/d 20.3 The photometry is based on nearby USNO-B1.0 star. USNO-B1.0_id R2 0877-0204059 15.98