TITLE: GCN CIRCULAR NUMBER: 16137 SUBJECT: GRB 140419A: KAIT Refined Analysis DATE: 14/04/21 05:21:29 GMT FROM: Weikang Zheng at UC Berkeley WeiKang Zheng, Alexei V. Filippenko, Adam Morgan (UC Berkeley), and S. B. Cenko (NASA/Goddard Space Flight Center) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory responded to Swift GRB 140419A (Marshall et al., GCN 16118) starting at 04:10:00 UT, 189 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. The bright optical afterglow (Zheng et al., GCN 16119; Guver et al., GCN 16120) was well detected in all three filters. Preliminary analysis shows that the afterglow decays with a single power law (with alpha = -1.15) from the beginning of our observations until about 3 hours later when the position moved beyond our reach. The power-law index is consistent with the value reported by Butler et al. (GCN 16121; GCN 16136). We find (V - I) about 1.7 mag (no extinction correction), and no obvious color change was detected during our observations. A preliminary light curve is posted at http://astro.berkeley.edu/~zwk/grb/GRB140419A/GRB140419A_kait.png