TITLE: GCN CIRCULAR NUMBER: 41927 SUBJECT: GRB 250917B: KAIT optical upper limit DATE: 25/09/21 08:31:40 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 triggered GRB 250917B (Caputo et al., GCN 41848; see also Fermi GBM Team, GCN 41846) starting at 06:29:01 UT, 77 seconds after the burst. A set of 10x20s, 10x40s and 50x60s clear (roughly R) filter images were obtained. We do not detect any new uncataloged source around Swift-XRT sources 1, 5 or 6 (Kennea et al., GCN 41851) neither in single image nor in coadd images. We estimate the limiting mag of ~21.5 (Vega) at a mid time of 45 minutes after the burst in our coadd image. View this GCN Circular online at https://gcn.nasa.gov/circulars/41927. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...