TITLE: GCN CIRCULAR NUMBER: 7846 SUBJECT: GRB 080607: ROTSE-III Detection of Optical Counterpart DATE: 08/06/07 06:11:50 GMT FROM: Wiphu Rujopakarn at U AZ/Steward W. Rujopakarn (Steward), E.S. Rykoff (UCSB), report on behalf of the ROTSE collaboration: ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 080607 (Swift trigger 313417). The first image was at 06:07:49.0 UT, 22.0 s after the burst (6.0 s after the GCN notice time). The unfiltered images are calibrated relative to USNO A2.0. We detect a 14.8 magnitude, fading source with coordinates: 12:59:47.3 +15:55:10.8 (J2000), with positional uncertainty of 1" or better start UT mag mlim(of image) ---------------------------------- 06:07:49.0 14.8 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/gsb313417_3b00_img.jpg Note that the object marked 11 is the candidate in question. Continuing observations are in progress.