TITLE:   GCN CIRCULAR
NUMBER:  19490
SUBJECT: GRB 160601A: Mondy optical observations, photometry of NOT sources
DATE:    16/06/02 14:35:18 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

E. Mazaeva (IKI),  E. Klunko (ISTP), A. Volnova (IKI),   I. Korobtsev
(ISTP),  A. Pozanenko (IKI) report on behalf of larger GRB follow-up
collaboration:

We observed the field of the Swift  GRB 160601A (Kocevski et al., GCN
19478) with AZT-33IK telescope of Sayan observatory (Mondy)  starting on 
June, 01 (UT) 15:00:41, i.e. 17 minutes after GRB trigger (GCN 19483). 
In a combined image we detected both NOT sources (Malesani et al., GCN 
19485) near enhanced XRT error circle (Evans et al., GCN 19484). 
Preliminary photometry (Vega) of the sources are following

Date        UT start   t-T0    Filter Exp.  NOT1          NOT2
                       (mid, days)     (s)

2016-06-01  15:00:41   0.04181  R    85*60  22.40+/-0.25  22.10+/-0.20

Photometry is based on nearby SDSS-DR9 stars, Lupton transformations into R:
SDSS-DR9_id            R(Lupton)
J153959.67+643325.7    16.72
J153956.37+643102.2    17.00
J153931.88+643247.0    17.02
J153927.50+643304.3    19.23
J153942.70+643016.4    16.27

A finding chart can be found at 
http://grb.rssi.ru/GRB160601A/GRB160601A_Mondy_160601_NOT_1_2.png