TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4379 SUBJECT: GRB 051221B: BOOTES optical observations. DATE: 05/12/22 01:36:01 GMT FROM: Javier Gorosabel at Danish Space Res Inst A. de Ugarte Postigo, M. Jelinek, S. Vitek, A.J. Castro-Tirado, J. Gorosabel, S.B. Pandey, S. Guziy (IAA-CSIC, Granada), P. Kubanek and R. Hudec (Astronomical Institute of the Academy of Sciences, Ondrejov), report: "BOOTES-1 in South Spain (El Arenosillo, INTA, Huelva), responded under non-optimal conditions to GRB 051221 (Swift trigger 173904, Boyd et al. GCNC 4376). A sequence of RVI-band exposures started at 20:07:15 UT (235s after the GRB onset). Preliminary analysis does not reveal any transient optical source in the 3' radius SWIFT/BAT error box, and in particular at the position reported by SWIFT/XRT (Page et al. GCNC 4378). We set the following R-band upper limits: ============================================= T-To (s) Exp. Time Lim. Mag. R-band Mid Exposure (s) (3 sigma) --------------------------------------------- 235 5 14.5 307 10 16.0 353 6x10 16.5 665 5x100+12x10 18.5 ============================================= We notice an important Galactic extinction in the GRB line of sight (E(B-V)=1.39, Schlegel et al. 1998)"