TITLE: GCN CIRCULAR NUMBER: 22812 SUBJECT: GRB 180620A: KAIT Optical Observations DATE: 18/06/20 20:13:48 GMT FROM: Weikang Zheng at UC Berkeley WeiKang Zheng and Alex 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 180620A (Evans et al., GCN 22798) starting at 08:37:19 UT, 141s 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, observations lasted about 3 hours. The optical afterglow (Evans et al., GCN 22790; Butler et al., GCN 22799; Elenin et al., GCN 22800; Tyurina et al., GCN 22801; Guidorzi et al., GCN 22803; Breeveld et al., GCN 22805; Watson et al., GCN 22806; Zhu et al., GCN 22811) was well detected in our V, I and clear filter images. A preliminary analysis shows that the afterglow rises at early time and peaked around 300s (also seen by Butler et al. GCN 22799; Watson et al., GCN 22806). After that the light curve shows monotonic decay, followed by a flat phase between ~1ks to ~3ks. A preliminary light curve is posted at: http://astro.berkeley.edu/~zwk/grb/GRB180620A/GRB180620A_kait.png