TITLE:   GCN CIRCULAR
NUMBER:  28621
SUBJECT: GRB 201013A: TSHAO and AbAO optical observations, afterglow confirmation
DATE:    20/10/14 16:20:40 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI), A. Pozanenko (IKI), V. Kim (AFIF, Pulkovo Observatory), 
  R. Ya. Inasaridze (AbAO), M. Krugov (AFIF), A. Volnova (IKI)  report 
on behalf of IKI-GRB-FuN:

We observed the field of Swift GRB 201013A (Page et al., GCN 28607; see 
also detection by CALET Tamura et al, GCN 28618) with  Zeiss-1000(W) 1-m 
telescope of Tien Shan Astronomical Observatory (TSHAO) and  AS-32 
telescope of Abastumani observatory (AbAO) in R-filter. Within  enhanced 
XRT position (Beardmore et al., GCN 28608),   at 1.6 arc seconds from 
the center of the position, we observed  an object mentioned by Jelinek 
et al. (GCN 28615) and  listed at least in the USNO-B.10 and PS1 
catalogs. Aperture photometry of the object are brighter than R2=16.22 
magnitude of the object in USNO-B1.0 1470-0207304 	 in both our 
observations. Flux subtraction of our photometry and  R2=16.22 result in 
photometry of possible afterglow suggested in earlier observations  by 
FRAM-ORM (Jelinek  et al. GCN 28615). Results of the flux subtraction 
assuming negligible error of R2 presented in USNO-B1.0 are following

  Date,     UT start, T0+   Exp.,  Filter, OT, Err., UL, observatory
                     (mid, days)

2020-10-13 21:44:47 0.79464 22*360 R    19.00 (+0.22 -0.18)  20.0 TSHAO
2020-10-13 23:33:56 0.84197 50* 60 R    19.39 (+0.08 -0.08)  21.3 AbAO

The photometry is based on nearby USNO-B1.0 star
USNO-B1.0_id R2
1470-0207278 14.89

While we cannot definitely detect fading the possible afterglow, the 
brightness of possible afterglow faded significantly between earlier 
(Jelinek  et al. GCN 28615) and our observations.

The cross section profile of the object in our observation at 
Zeiss-1000(W) of TSHAO is differ from point like source. The reason of 
the extended profile might be due to offset of the afterglow from the 
foreground star  or could be due to the object USNO-B1.0	1470-0207304 is 
not the star but a galaxy. In the latter case, USNO-B1.0 may be a small 
neighboring host galaxy GRB 201013A.