TITLE: GCN CIRCULAR NUMBER: 18135 SUBJECT: GRB 150811A: KAIT Refined Analysis DATE: 15/08/12 21:40:27 GMT FROM: Xiang-Gao Wang at GuangXi U Xianggao Wang (UC Berkeley, GXU, UNLV), WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory responded to Swift GRB 150811A (Evans et al., GCN 18119) starting at 04:09:05 UT, 176 s after the burst. Observations were performed with an automatic sequence in the V, I, and clear (roughly R) filters, and the exposure time was 20 s per image. Due to a focus problem, the first useful image started at about 364 s after burst, and observations lasted about 5.5 hours later. The optical afterglow (Butler et al., GCN 18120; GCN 18132, Zheng et al., GCN 18121, Kuin et al., GCN 18122; 18131, Japelj et al., GCN 12123, Perley & Cenko, GCN 12125, Moskivitin, GCN 12128) was well detected in I filters. We confirm the peak of the OT around ~13 m reported by Perley & Cenko (GCN 12125). After 3 ks after the burst, the light curve can be fit by a power law with index of -1.02, consistent with the value reported by Butler et al. (GCN 18132). A preliminary light curve is posted at: http://astro.berkeley.edu/~zwk/grb/GRB150811A/GRB150811A_kait.png