TITLE:   GCN CIRCULAR
NUMBER:  9597
SUBJECT: GRB 090618: RTT150 optical observations
DATE:    09/06/30 14:12:04 GMT
FROM:    Irek Khamitov at TUG  <irekk@tug.tug.tubitak.gov.tr>

I. Khamitov, M. Parmaksizoglu, T. Ak, Z. Eker (TUG),
Z. Aslan (Kultur Uni.), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.)
R. Burenin, M. Pavlinsky, R. Sunyaev (IKI),
I. Bikmaev, N. Sakhibullin (KSU/AST),

report:

We observed the OT (Schady et al., GCN 9512; Cenko et al., GCN 9513; 
Perley, GCN 9514; Rujopakarn et al., GCN 9515) of the Swift GRB 090618 
with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK 
National Observatory, Turkey), in Rc band during three nights 25,26 and 27 
June 2009 and in B band in 26 June.

Every night we made 3x900s exposures in Rc band and in 26 June we made 
additionally 3x900 in B band. The OT is detected in all stacked images in 
Rc. The brightness of OT is not changed inside of photometric error.
Our preliminary estimate of its magnitude during these observations is
m_Rc=22.3+/-0.1 (7.68, 8.64, 9.58 days after the burst).

We found no OT on stacked B-image. The limiting magnitude of the frame is 
mlim_B=23.4 (8.68 days after the burst).


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