TITLE: GCN CIRCULAR NUMBER: 8228 SUBJECT: GRB 080915: ROTSE-III Optical Limits DATE: 08/09/15 00:45:01 GMT FROM: Wiphu Rujopakarn at U AZ/Steward W. Rujopakarn (Steward), H. Swan (U Mich), T. Guver (U Arizona) report on behalf of the ROTSE collaboration: ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to GRB 080915 (Swift trigger 324744; Oates et al., GCN 8227), producing images beginning 11.2 s after the GCN notice time. An automated response took the first image at 00:03:42.2 UT, 52.2 s after the burst, under cloudy conditions. These observations were affected by the full moon. We took 10 5-sec, and 1 20-sec exposures. These unfiltered images are calibrated relative to USNO A2.0 (R). Imaging is on going. Comparison to the DSS (second epoch) reveals no new sources within the 3-sigma Swift/BAT error circle. Individual images have limiting magnitudes ranging from 14.0-14.3; we set the following specific limit. start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------- 00:03:42.2 00:03:47.2 5 14.2 52.2 N