GCN Circular 41970
Subject
GRB 250924A: KAIT optical observations
Event
Date
2025-09-24T17:33:43Z (15 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, automatically responded to the Swift GRB
250924A (Siegel et al., GCN 41959) starting at 08:21:50 UT, 201s
after the burst. Observations lasted for about 1 hour with degraded
sky condition (cloudy), and a set of clear (roughly R) filter images
were obtained. We clearly detected the reported fading afterglow
(Siegel et. al, GCN 41959; Becerra et. al, GCN 41960; Schneider
et. al, GCN 41963; Freeberg et. al, GCN 41968; Pankov et al.,
GCN 41969). We measure its brightness decayed from 16.41 +/- 0.03
mag (Vega) at 3.52 minutes to 19.7 +/- 0.3 mag at 59.33 minutes after
the burst. The data after 300s can be fit with a single power law
with a decay index of -0.96 +/- 0.02.