[vsnet-grb-info 9786] GRB 100906A: RTT150 optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  11254
SUBJECT: GRB 100906A: RTT150 optical observations
DATE:    10/09/07 18:30:39 GMT
FROM:    Rodion Burenin at IKI, Moscow  <rodion at hea.iki.rssi.ru>

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


The optical counterpart of GRB 100906A (GCN 11227) was observed with
Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National
Observatory, Turkey), starting at Sep 06, 19:28 UT, i.e. ~5.64 hours after
the burst, using TFOSC.

Three series of BRI frames were made under moderate weather conditions. The
afterglow is clearly detected in all images.

Assuming the star at RA = 01:54:46.82, Dec. = +55:37:55.3 to have USNOB1.0
R2MAG = 15.70, we estimated the following magnitudes for the OT on combined
images of every set:

 t-t0     band   mag   err	
 6.048 h    R   18.80  0.02
 9.610 h    R   19.08  0.02
13.554 h    R   19.69  0.04

The color of the afterglow changes from (B-R)=1.21 to (B-R)=1.31 at the
beniginning and at the end of our observations.