TITLE: GCN CIRCULAR NUMBER: 10917 SUBJECT: GRB 100702: ROTSE-III Optical Limits DATE: 10/07/02 01:44:13 GMT FROM: Heather Flewelling at IfA/Hawaii H. Flewelling (IfA/Hawaii), W. Zheng (U Mich), S. B. Pandey (U Mich), W. Rujopakarn (Steward), report on behalf of the ROTSE collaboration: ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to GRB 100702 (Swift trigger 426438; M. H. Siegel, GCN 10916), producing images beginning 7.7 s after the GCN notice time. An automated response took the first image at 01:04:06.7 UT, 19.5 s after the burst, under fair 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 severely crowded. Individual images have limiting magnitudes ranging from 15.6-15.9; we set the following specific limits. start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------- 01:04:06.7 01:05:22.8 76 16.1 19.5 Y 01:20:08.4 01:24:48.5 280 16.2 981.2 Y