TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5524
SUBJECT: GRB 060904B: RTT150 optical observations
DATE:    06/09/04 19:32:33 GMT
FROM:    Alexander Mescheryakov at IKI RAN  <gardel@hea.iki.rssi.ru>

 A. Mescheryakov, R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), 
 I. Khamitov, Z. Aslan (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.), 
 I. Bikmaev, N. Sakhibullin (KSU/AST)
 
 report:
 
 We observed the optical counterpart of GRB 060904B (Grupe et al., GCN
 5505; Rykoff et al., GCN 5504; D. Fugazza et al., GCN 5513) with
 Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National
 Observatory, Turkey). The observations were started at 02:39:35 UT,
 i.e. 8.21 min after the trigger and were ended approximately 20 min 
 later due to sunrize. We made series of 30 s exposures in R and also 
 few exposures in B and V.
 
 We estimate the following magnitudes for the OT:
 
 UT        t-t0    Rc      err
 --------------------------------------------------------- 
 2:39:50   8:46    16.75   0.02
   41:00   9:58    16.86   0.03
   42:09  11:05    16.99   0.03
   43:19  12:15    17.05   0.04
   44:29  13:05    17.22   0.05
   45:39  14:35    17.34   0.06
   47:58  16:54    17.48   0.09
   49:07  18:03    17.50   0.09
   50:17  19:13    17.64   0.10
 
 The magnitudes are derived using comparison stars from the USNO-B1
 catalog.
 
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