GCN Circular 41481
Subject
GRB 250821A: KAIT optical upper limit
Event
Date
2025-08-21T23:35:44Z (3 days ago)
From
Weikang Zheng at UC Berkeley <weikang@berkeley.edu>
Via
email
WeiKang Zheng (UCB) and Alexei V. Filippenko (UCB) 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 GRB 250821A (Dichiara
et al., GCN 41462) starting at 12:02:57, Aug. 21 UT, ~1.28 hours
after the burst. A set of 9x60s clear (roughly R) filter images
were obtained under twilight conditions. We do not detect any new
optical counterpart candidate within the Enhanced XRT error circles
(Beardmore et al., GCN 41472) in the co-add image. Our upper limit
is about 20.0 (Vega) mag at a mid time of 1.30 hours after the burst.
Our result is consistent with the optical upper limit reported by
other groups (Strausbaugh et al., GCN 41466; Oates et al., GCN 41471;
Lipunov et al., GCN 41478).