TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4196 SUBJECT: GRB 051105A, optical observations DATE: 05/11/05 18:19:45 GMT FROM: Sylvio Klose at TLS Tautenburg S. Klose, U. Laux, and B. Stecklum, Thueringer Landessternwarte Tautenburg, report: Tautenburg started observing the error circle of GRB 051105A (Cummings et al. 2005) on Oct 05, 16:37 UT, i.e. about 10 hrs after the burst. Among the XRT sources reported in GCN 4195 (Mineo et al. 2005), only source S1 lies within the r=2.5 arcmin GRB error circle (Barbier et al. 2005, GCN 4194). This source is close to a galaxy. Since we can resolve this galaxy its redshift might be less than 0.5. A first inspection of the combined R-band image (9x5 min) shows two sources in the 6.5 arcsec error circle (S1). The brighter one at RA, DEC (J2000) = 17:41:10.05, 34:55:43.5 (+/- 1 arcsec, is barely visible on the DSS2, the fainter one, at RA, DEC = 17:41:10.21, 34:55:41.4 (+/- 1 arcsec), is beyond the limiting magnitude of the DSS2. Observations are ongoing. This message my be quoted.