TITLE: GCN CIRCULAR NUMBER: 6948 SUBJECT: GRB 071020A: ROTSE-III Detection of Optical Counterpart DATE: 07/10/20 07:17:21 GMT FROM: Brad Schaefer at LSU B. E. Schaefer (Louisiana State), T.A. McKay (U Mich), F. Yuan (U Mich), report on behalf of the ROTSE collaboration: ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 071020A (Swift trigger 294835). The first image was at 07:02:52.5 UT, 25.6 s after the burst (9.5 s after the GCN notice time). The unfiltered images are calibrated relative to USNO A2.0. We detect a 13.6 magnitude, fading source with coordinates: 07:58:39.9 +32:51:41.4 (J2000), with positional uncertainty of 1" or better start UT mag mlim(of image) ---------------------------------- 07:02:52.9 13.6 16.4 This source is not visible in DSS (second epoch), 2MASS or the MPChecker database. A jpeg image is available at http://www.rotse.net/images/gsb294835_3b00_img.jpg Continuing observations are in progress.