TITLE: GCN CIRCULAR NUMBER: 7349 SUBJECT: GRB 080303A: ROTSE-III Optical Limits DATE: 08/03/03 09:38:13 GMT FROM: Brad Schaefer at LSU B. E. Schaefer (Louisiana State) and W. Rujopakarn (Steward), report on behalf of the ROTSE collaboration: ROTSE-IIIa, located at Siding Spring Observatory, Australia, responded to GRB 080303A (Swift trigger 304549), producing images beginning 8.4 s after the GCN notice time. An automated response took the first image at 09:10:55.3 UT, 20.0 s after the burst, and during the gamma-ray emission, under twilight conditions. We took 10 5-sec, 10 20-sec and 10 60-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 or the XRT error circle, for both single images and coadding into sets of 10; the field is not crowded. Individual images have limiting magnitudes ranging from 13.3-15.8, with the poor limits at the start due to the bright twilight that was rapidly fading. We set the following specific limits. start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------- 09:10:55.4 09:11:00.4 5 13.3 20.1 N 09:10:55.4 09:13:06.9 131 14.1 20.1 Y 09:21:35.1 09:29:30.1 475 16.2 659.8 Y