TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2907 SUBJECT: GRB041223: optical and NIR observations with REM DATE: 04/12/24 16:37:59 GMT FROM: Daniele Malesani at SISSA-ISAS,Trieste,Italy S. Covino, F.M. Zerbi, E. Palazzi, G. Chincarini, G. Tagliaferri, E. Molinari, V. Testa, G. Tosti, A. Monfardini, A. Di Paola, M. Rodoṇ, L.A. Antonelli, P. Conconi, G. Cutispoto, P. D'Avanzo, L. Nicastro, on behalf of the REM/ROSS team, report: We imaged the field of GRB 041223 (Tueller et al., GCN 2898; Burrows et al., GCN 2901) with the robotic 60-cm REM telescope located at La Silla, Chile. Observations were carried both in the NIR and in the optical, on 2004 Dec 24 from 02:37 UT to 03:11 UT (i.e. ~12 hours after the burst). REM was equipped with the REMIR near-IR camera (10x10 sq arcmin FoV, JHK filters) and the ROSS optical spectrograph/imager (10x10 sq arcmin FoV, VRI filters). Observations were performed under good seeing conditions. The net exposure times were: J: 500s; H: 500s; K: 500s; V: 150s; R: 150s; I: 150s. The comparison with the 2MASS catalog did not reveal new infrared sources with S/N>5 at the limit of the catalog. In particular no source is present at the position of the X-ray afterglow detected by Swift-XRT (Burrows et al. GCN 2901) and of the optical transient reported by Berger et al. (GCN 2902) and Malesani et al. (GCN 2903). Also the optical observations, partly affected by the bright Moon, did not show any convincing candidate. The 3-sigma upper limit in the R band is R ~ 18. This message is citeable.