TITLE:   GCN CIRCULAR
NUMBER:  16156
SUBJECT: GRB 140423A: KAIT Optical Detection
DATE:    14/04/23 18:58:38 GMT
FROM:    Weikang Zheng at UC Berkeley  <zwk@astro.berkeley.edu>

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), located at
Lick Observatory, responded to Swift GRB 140423A (Sonbas et al.,
GCN 16142) starting at 08:33:55 UT, 122 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 (Elenin et al., GCN
16143; Kaur et al., GCN 16144; Ferrante et al., GCN 16145; Chester
et al., GCN 16147; Maehara et al., GCN 16151; Cenko et al., GCN
16153) was well detected in all three filters. Preliminary analysis
shows that the afterglow had a rather broad peak at t = 150-250 s with
R ~ 14.3 mag. It decayed faster after ~1000 s, with a single power
law having alpha about -1.7. A preliminary light curve is posted at
http://astro.berkeley.edu/~zwk/grb/GRB140423A/GRB140423A_kait.png