TITLE: GCN CIRCULAR NUMBER: 9667 SUBJECT: GRB 090715A: ROTSE-III Optical Limits DATE: 09/07/15 17:47:35 GMT FROM: Shashi Bhushan Pandey at ARIES, INDIA S. B. Pandey (U Mich), S.A. Yost (College of St. Benedict), W. Zheng, F. Yuan (U Mich), report on behalf of the ROTSE collaboration: ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to the short-hard GRB 090715A (Swift trigger 357498, Racusin J. L., GCN 9666), producing images beginning 7.1 s after the GCN notice time. An automated response took the first image at 17:26:05.1 UT, 25.9 s after the burst, under fair conditions. We took 10 5-sec and 10 20-sec exposures and imaging is ongoing. These unfiltered images are calibrated relative to USNO A2.0 (R). Comparison to the DSS (second epoch) reveals no new sources within the 3-sigma Swift/BAT error circle, for both single images and coadding into sets of 10. Individual images have limiting magnitudes ranging from 15.4-16.6; we set the following specific limits. start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------- 17:26:05.1 17:27:21.5 76 16.8 25.9 Y 17:27:36.4 17:32:18.5 282 17.4 117.2 Y