TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3084 SUBJECT: GRB 050306: further TAROT optical data DATE: 05/03/10 17:46:14 GMT FROM: Michel Boer at Obs Haute Prov. Klotz, A., Boer M. (OHP), Atteia, J.L., and G. Stratta (LATT) report: We analyzed images taken 1 hour after GRB 050306 (cf. Markwardt et al. GCNC 3071) with the TAROT robotic telescope (D=25cm) located at the Calern observatory, France. The source was at an elevation of 22 to 26 degrees above the horizon but images are of good quality. We coadded 29 images of 30s with no filter. No new source was detected at the limiting magnitude R~17.5 after a comparison with the DSS2 R and 2MASS images and the USNO-B1 catalogue. We summarize below the limiting magnitude obtained by TAROT: Date from to Rmag Remarks 2005-03-06 04:18:54 04:53:02 >17.5 45 to 80 min after GRB We also revised the limiting magnitude of the following measurement 14.0 6 min after the end of prompt emission We analyzed the 2MASS catalogue to extract the galactic extinction through the line of sight of GRB050306. We used the method described in Klotz et al. (A&A 2004, 425, p427). From Earth to a distance modulus of about 9.5-10.5, the visual extinction is Av=2 +/-1. The 2MASS data don't allow probing farer distances. TAROT data for this GRB is summarized at the following URL: http://www.cesr.fr/~klotz/grb050306/ This message is citable.