[vsnet-grb-info 28479] GRB 210731A: KAIT Optical Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30582
SUBJECT: GRB 210731A: KAIT Optical Detection
DATE:    21/08/02 09:19:57 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 the Swift GRB 210731A (Troja et al.,
GCN 30568) starting at ~9.04 hours after the Swift trigger.
A total of 30x60s images were obtained in the clear (roughly R)
filter. The optical afterglow (de Wet et al., GCN 30571; Kuin et al.,
GCN 30572; Guelbenzu et al., GCN 30574; Lipunov et al., GCN 30578;)
was clearly detected in each single image. We measured its brightness
of 18.6 +/- 0.1 mag at 9.26 hours after burst, calibrated to the
Pan-STARRS1 catalog.