TITLE: GCN CIRCULAR NUMBER: 40171 SUBJECT: GRB 250419A: KAIT optical afterglow observations DATE: 25/04/19 06:04:42 GMT FROM: Weikang Zheng at UC Berkeley weikang@berkeley.edu

WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) 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 SVOM GRB 250403A (Wang

et al., GCN 40168) with a set of clear (roughly R) images starting

at 1.47 hours after the trigger. We clearly detected the optical

afterglow (López et al., GCN 40169; Xin et al., GCN 40170) in our

single image. The afterglow is measured at 18.0 +/- 0.2 mag (Vega)

at 1.47 hours after the trigger. It remained to be similar brightness

for about 40 minutes then decayed after that. Observation is on

going.

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