TITLE:   GCN CIRCULAR
NUMBER:  23287
SUBJECT: GRB 180914B: RTT150 optical observations
DATE:    18/10/01 20:36:17 GMT
FROM:    Rodion Burenin at IKI, Moscow  <rodion@hea.iki.rssi.ru>

A. Lyapin, I. Zaznobin, R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), 
I. Bikmaev, E. Irtuganov, N. Sakhibullin (KFU/AST),
I. Khamitov, S. Ozdemir (TUG), E. Gogus (Sabanci Uni.)

report:

We observed the field of GRB 180914B (Ursi et al., GCN 23226, Bissaldi
et al., GCN 23232, Ai et al., GCN 23236) with the Russian-Turkish
1.5-m optical telescope (RTT150, Bakirlitepe, TUBITAK National
Observatory, Turkey) using the TFOSC instrument.

We obtained series of exposures in SDSS gri filters, starting at 18:30
UT on Sep 16, 2018. The optical transient (Zhen and Filippenko, GCN
23237, Troja et al., GCN 23238, de Ugarte Postigo et al., GCN 23239)
was detected in all images. We estimated the following magnitudes for
the OT:

g:  20.97 +- 0.02
r:  20.38 +- 0.02 
i:  20.04 +- 0.02

calibrated against SDSS secondary standards.