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.