TITLE:   GCN CIRCULAR
NUMBER:  6575
SUBJECT: GRB070621: RTT150 optical observations
DATE:    07/06/23 14:22:12 GMT
FROM:    Irek Khamitov at TUG  <irekk@tug.tug.tubitak.gov.tr>

I. Khamitov (TUG), I. Bikmaev, N. Sakhibullin (KSU/AST),
Z. Tunca (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.),
R. Burenin, M. Pavlinsky, R. Sunyaev (IKI)

reports:

We observed the field of GRB 070621 (Sbarufatti et al., GCN 6530) with
Russian-Turkish 1.5-m telescope (RTT150, Bakyrlytepe,TUBITAK National
Observatory, Turkey). We made 16x60s exposures in R band, starting at June
21, 23:25:40UT, i.e. approximately 500 s after the burst.

We detected no sources inside the XRT error circle in any of 60~s image,
as well as in combined 16x60~s image with 3-sigma limiting magnitudes
m_R=~20.8 and m_R=~22.3 respectively.

The source reported by Melesani et al (GCN 6565) is clearly detected on 
the level m_R=22.15+/-0.2 using the same reference star USNO-B1 
0651-0871887, i.e. is not variable within the errors. The astrometric 
position of this source is RA=21:35:10.12, DEC=-24:49:07.2 with 0.1 arcsec 
accuracy.

The sourse to the east from XRT position, which was found in Gemini
South data (s4, Bloom et. al., GCN 6568), and in image from Keck II LGS
AO (i2, Bloom et. al., GCN 6572) is also detected marginally near the
limit of our combined image.

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