TITLE:   GCN CIRCULAR
NUMBER:  28656
SUBJECT: GRB 201015A: CrAO/ZTSH optical observations
DATE:    20/10/16 15:31:16 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI),  N. Pankov (HSE), A. Pozanenko (IKI), V. Rumyantsev 
(CrAO),  A. Volnova (IKI)  report on behalf of larger GRB follow-up 
collaboration:

We observed the GRB 201015A  (D'Elia et al., GCN 28632) with ZTSH 2.6m 
telescope of CrAO observatory between Oct. 16 (UT) 01:02:14 -- 02:52:23. 
  The optical afterglow  (e.g., Lipunov et al., GCN 28633; Kennea et 
al., GCN 28635; Malesani et al., GCN 28637; Ackley et al., GCN 28639; Hu 
et al., GCN 28645; Zhu et al., GCN 28653) at redshift z=0.426 (de Ugarte 
Postigo et al., GCN 28649) is clearly detected in each frame of 120 s 
exposure in R filter.

The exact photometry of the afterglow depends on the underlying object 
visible and presented in PS1 catalogue (i'=19.6), which may be a host 
galaxy (PS1 magnitude i'=19.6). Preliminary photometry of the afterglow 
in a combined image is following

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


2018-10-16 02:19:26  0.15501 R      12*120   20.66   0.05   23.0


The photometry is based on several nearby USNO-B1.0 stars
USNO-B1.0_id R2
1434-0471702 17.51
1434-0471746 18.23