TITLE: GCN CIRCULAR NUMBER: 8399 SUBJECT: GRB 081024A: ROTSE-III Optical Limits DATE: 08/10/24 06:33:52 GMT FROM: Brad Schaefer at LSU B. E. Schaefer (Louisiana State), E.S. Rykoff (UCSB), H. Swan (U Mich), W. Rujopakarn (Steward), report on behalf of the ROTSE collaboration: ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 081024A (Swift trigger 332516; G. Stratta, GCN 8398), producing images beginning 9.1 s after the GCN notice time. An automated response took the first image at 05:53:37.2 UT, 28.4 s after the burst, under excellent conditions. We took 10 5-sec, 10 20-sec and 40 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; however, we are limited as the field is somewhat crowded. Individual images have limiting magnitudes ranging from 16.1-17.1; we set the following specific limits. start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------- 05:53:37.1 05:53:42.1 5 16.2 28.3 N 05:54:57.0 05:59:37.7 280 17.2 108.2 Y