TITLE: GCN CIRCULAR NUMBER: 41970 SUBJECT: GRB 250924A: KAIT optical observations DATE: 25/09/24 17:33:43 GMT FROM: Weikang Zheng at UC Berkeley <weikang@berkeley.edu> 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/41970. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...