TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3929 SUBJECT: GRB 050904: BOOTES early R-band observation DATE: 05/09/06 15:34:03 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia M. Jelinek, A.J. Castro-Tirado, A. de Ugarte Postigo (IAA-CSIC Granada), P. Kubanek (ASU AV CR Ondrejov), S. Vitek (CVUT Praha), J. Gorosabel and S. Guziy (IAA-CSIC), R. Hudec (ASU AV CR), J.M. Castro Ceron (DARK NBI Kobenhavn), P. Pata and M. Bernas (CVUT), report: The BOOTES-1B 30 cm robotic telescope in Southern Spain, has followed-up the high-redshift GRB 050904 (Cummings et al. GCN 3910, Haislip et al. 3913, 3914, Reichart et al. 3915, Antonelli et al. GCN 3924) starting 124s after the onset of the burst. The upper limits derived from our R-band filter measurements during the time interval 124s -1100s after the event, together with the values reported by TAROT (Klotz et al. GCN 3917) are consistent with an early decay index of alpha = -1.2 (i.e. in agreement with the value reported at a later epoch in the J-band by Haislip et al. GCN 3914). This message can be quoted. [GCN OPS NOTE(06sep05): Per author's request: "NBI" --> "DARK NBI", added "Haislip et al. 3913, 3914, Reichart et al. 3915,", "our R-band meaurements" --> "our R-band filter measurements", "the value later reported" --> "the value reported at a later epoch".] [GCN OPS NOTE(21oct05): Per author's request: in the Subject line "detection" is changed to "observation", and in the body "Our R-band filter measurements" is changed to "The upper limits derived from our R-band filter measurements".]