[vsnet-grb-info 21189] GRB 180914B: RTT150 optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23288
SUBJECT: GRB 180914B: RTT150 optical observations
DATE:    18/10/01 20:38:00 GMT
FROM:    Rodion Burenin at IKI, Moscow  <rodion at hea.iki.rssi.ru>

E. Irtuganov, I. Bikmaev, N. Sakhibullin (KFU/AST),
A. Lyapin, I. Zaznobin, R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), 
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 direct images in SDSS r filter, on Sep 18, 19 and 21,
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:

Sep 18:  21.21 +- 0.03
Sep 19:  21.99 +- 0.05
Sep 21:  22.28 +- 0.10

calibrated against SDSS secondary standards.

Therefore, approximately power law light curve is observed, with a
decay slope near -1.53, which is approximately consistent with the
slope measured earlier by Kann et al., GCN 23256. Note, that some
deviations from simple power law decay at the level of 0.2-0.3 mag are
also observed in our data.