TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5177
SUBJECT: GRB 060526: RTT150 optical observations, afterglow flattening
DATE:    06/05/28 15:00:31 GMT
FROM:    Irek Khamitov at TUG  <irekk@tug.tug.tubitak.gov.tr>

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

report:

We observed the field around position of optical counterpart of
GRB060526 (Campana et al. GCN 5162; French & Jelinek GCN 5165; Rykoff et
al. GCN 5166) with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe,
TUBITAK National Observatory, Turkey). The observations were made in BVR
in two epochs: May. 27, 18:40UT and 23:20UT (26.19 and ~30.86 hours
after the burst). The afterglow is detected clearly in VRc bands and
marginally in B.

Using Landolt standards we calibrate reference star used in our GCN 5173
and estimate its Rc magnitude as 16.484+/-0.01, 0.13 mag fainter then
R2MAG of USNO-B1.

We estimate the following Rc magnitudes for the OT:

    t-t0  m_R     err
   26.31  20.581  0.04
   31.57  20.641  0.04

These magnitudes significantly deviates from power-law decay with index
-1.2. The flare detected by Halpern et al. (GCN5176) is continued by the
flattening of afterglow light curve.

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