TITLE:   GCN CIRCULAR
NUMBER:  28550
SUBJECT: GRB 201001A: TSHAO optical upper limit
DATE:    20/10/02 14:39:28 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI), I. Reva (FAPHI), A. Pozanenko (IKI)  report on behalf 
of GRB-IKI-FuN:

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