[vsnet-grb-info 20935] GRB 180720B: KAIT Optical Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23033
SUBJECT: GRB 180720B: KAIT Optical Observations
DATE:    18/07/25 00:12:38 GMT
FROM:    Weikang Zheng at UC Berkeley  <weikang at berkeley.edu>

WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on
behalf of the KAIT GRB team:

The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, observed the field of Swift GRB 180720B
(Siegel et al., GCN 22973) each night from 21 to 24 UT, at a mean time
of 0.855, 1.886, 2.883 and 3.874 days, respectively, after the burst.
Observations were performed with a sequence in the B, V, R, I and
clear (roughly R) filters, and the exposure time was 60 s per image.
The optical afterglow (Martone et al., GCN 22976) was clearly detected
and we measure its clear band mag to be 18.5, 19.6, 20.5 and 20.9,
respectively, calibrated to the SDSS catalog.