TITLE: GCN CIRCULAR NUMBER: 27329 SUBJECT: GRB 200306C: BOOTES-1 detection of the optical afterglow DATE: 20/03/07 00:04:48 GMT FROM: Alberto J. Castro-Tirado at IAA-CSIC Y.-D. Hu, A. J. Castro-Tirado and E. Fernandez-Garcia (IAA-CSIC), C. Perez del Pulgar, A. Reina, A. Castellon, I. Carrasco, I. Perez-Garcia (UMA), F. Rendon (IAA-CSIC and INTA-CEDEA), on behalf of a larger collaboration, report: The 30cm BOOTES-1 robotic telescope at INTA-CEDEA in Huelva (Spain) automatically responded to the Swift trigger of GRB 200306C (Gropp et al., GCNC 27326). A sequence of 1-s images (clear filter) were obtained starting at 22:52:28 UT (i.e. 109s after the burst). At the UVOT position reported by Swift an optical transient is detected with R = 14.9, in agreement with the MASTER (Lipunov et al. GCNC 27324) and FRAM detections (Jelinek et al. GCNC 27328). A detailed analysis for the sequence of images which were obtained is ongoing. The magnitude is calibrated against the USNO-B1 catalog and is not corrected for Galactic extinction in the direction of the GRB. We thank the staff at INTA-CEDEA for its excellent support.