[vsnet-grb-info 14823] GRB 140419A: KAIT Refined Analysis

[GCN Circulars]

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  <zwk at 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) 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