TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2904 SUBJECT: GRB 041218: TAROT optical observations DATE: 04/12/24 13:58:37 GMT FROM: Michel Boer at Obs Haute Prov. GRB 041218: Optical observations Klotz, A., Boer M. (OHP), Atteia, J.L., and G. Stratta (LATT) report: The field of GRB 041218 (Mereghetti, et al., GCNC 2858) was observed with the TAROT 25 cm robotic telescope at Calern, France. The unfiltered observations started at 2004 December 18 17:12 UT (beginning of the night). Due to a technical problem images were slightly defocused. We co-added 129 frames of 30s from 17:12 to 18:50 UT. The associated OT described by Torii (GCNC 2860) is detected 0.5 mag fainter than the nearby star USNO-B1 1613-0027278. Hence, we estimate its magnitude, R = 19.4 +/- 0.2. We analyzed the 2MASS catalogue to extract the galactic extinction through the line of sight of GRB041218. We used the method described in Klotz et al. (A&A 2004, vol 425, p427). From Earth to a distance modulus of about 8, the visual extinction is Av=1.45. The 2MASS data doesn't allow probing farer distances. This message can be cited.