TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3580 SUBJECT: GRB 050713A: ROTSE-III Optical Limits DATE: 05/07/13 05:16:29 GMT FROM: Sarah Yost at U.Michigan S.A. Yost, E.S. Rykoff, W. Rujopakarn (U Mich), K. Alatalo (Berkeley), B. Schaefer (Louisiana State) report on behalf of the ROTSE collaboration: ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 050713A (Swift trigger 145675), producing images beginning 10.7 s after the GCN notice time. An automated response took the first image at 04:29:24.8 UT, 22.4 s after the burst, under fair conditions. We took 10 5-sec, 10 20-sec and 10 60-sec eposures. 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 error circle or at the XRT position, for both single images and coadding into sets of 10. Individual images have limiting magnitudes ranging from 16.2-17.7; we set the following limit, noting it is adversely affected by the glare from the nearby bright star SAO 10034 (V=6.6), 67" from the XRT position. start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------- 04:29:24.8 4:30:46.8 82 17.7 22.4 Y