TITLE: GCN CIRCULAR NUMBER: 14525 SUBJECT: GRB 130427A: KAIT optical observations DATE: 13/05/02 07:17:53 GMT FROM: Weikang Zheng at U.of Michigan WeiKang Zheng, S. Bradley Cenko, Alexei V. Filippenko and Adam Morgan (UC Berkeley) report on behalf of the KAIT GRB team: We observed the afterglow of GRB 130427A (e.g., Maselli et al., GCN 14448; Elenin et al., GCN 14450; Perley, GCN 14451) with the 0.76-m Katzman Automatic Imaging Telescope (KAIT) located at Lick Observatory on Apr. 28, 29, 30, and May 1 UT. Observations were carried out in the B, V, R, and I filters. A series of images, lasting for about an hour, was taken on each night. The afterglow is well detected in all filters, and the estimated R-band magnitudes (calibrated to SDSS, transformed to R) are as follows, with times relative to the BAT trigger: t_mid(hr) exp(s) R(mag) err 20.2 60.0 17.4 +/- 0.1 45.1 60.0 18.5 +/- 0.1 69.1 360.0 19.1 +/- 0.1 93.1 600.0 19.6 +/- 0.2 A power-law fit to the data shows the afterglow continues to decay with an index of roughly -1.0 (Itoh et al., GCN 14486). Further observations are planned.