TITLE: GCN CIRCULAR NUMBER: 6303 SUBJECT: GRB 070419A: ROTSE-III Optical Limits DATE: 07/04/19 10:33:32 GMT FROM: Brad Schaefer at LSU B. E. Schaefer (Louisiana State), F. Yuan (U Mich), S.A. Yost (U Mich), report on behalf of the ROTSE collaboration: ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 070419A (Swift trigger 276205), producing images beginning 6.3 s after the GCN notice time. An automated response took the first image at 10:00:47.3 UT, 81.2 s after the burst, under excellent conditions. We took 10 5-sec, 10 20-sec and 20 60-sec eposures, with further exposures still continuing. These unfiltered images are calibrated relative to USNO A2.0 (R). There is a bright star in the BAT error circle, but this is well removed from the XRT position. Comparison to the DSS (second epoch) reveals no new sources within the 3-sigma 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 15.2-17.6; we set the following specific limits. start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------- 10:00:47.3 10:00:52.3 5 16.0 81.2 N 10:00:47.3 10:01:54.4 67 17.8 81.2 Y