[vsnet-grb-info 20936] GRB 180721A: KAIT Optical Upper Limit

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23034
SUBJECT: GRB 180721A: KAIT Optical Upper Limit
DATE:    18/07/25 00:13:00 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, responded to Swift GRB 180721A (Sbarufatti et al.,
GCN 22994) starting at 11:25:23 UT, ~19 minutes after the burst.
Observations were performed with an automatic sequence in the
clear (roughly R), V, and I filters, and the exposure time was 20 s
per image. We do not detect any optical afterglow candidate within
the enhanced XRT position error circle (Goad et al., GCN 22997)
neither in single image, nor in the co-add images.
The typical limiting magnitude of our single clear image is about
19.5 mag calibrated to the Pan-STARRS1 catalog.