TITLE: GCN CIRCULAR NUMBER: 11427 SUBJECT: GRB 101123A: ROTSE optical observations DATE: 10/11/29 23:41:57 GMT FROM: W.K. Zheng at NAOC W. Zheng, S. B. Pandey and C. Akerlof (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 GRB 101123A (Fermi/GBM trigger 312245496 / 101123952: Guiriec, GCN 11423; localized by IPN: Hurley et al., GCN 11424) 107s after the burst. Observation was performed in 2x2 tiling mode, covered totally ~3.6x3.6 square degrees around the center of GBM trigger. Observation lasted for ~1.3 hours with 20s exposure time for each image. The location of the two OT candidates reported by Gorbovskoy et al. (GCN 11426) were both covered by ROTSE images. For candidate 1, the first ROTSE image was started at 2010-11-23 22:54:50.91, 196s after the burst. For candidate 2, the first ROTSE image was started at 2010-11-23 22:53:51.31, 136s after the burst. We do not detected any point source at either of the two candidate locations in the single or the co-added images. The limiting magnitude is ~16.0 mag for single image and ~16.7 mag for co-added images.