TITLE: GCN CIRCULAR NUMBER: 40401 SUBJECT: EP250508a: KAIT optical upper limit DATE: 25/05/08 18:38:55 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 EP250508a (Liang et al.,

GCN 40390) starting at 06:17, May 08 UT, about 14 minutes after

the burst. A set of clear (roughly R) filter images were obtained.

Preliminary analysis do not reveal any new optical counterpart

candidate within the X-ray afterglow error circles (Liang et al.,

GCN 40390; Zhao et al., GCN 40399). Due to the bright moonlight,

our image quality are degraded and we estimate the limiting

magnitude of our single image to be ~17.0 mag, shallower than the

upper limit reported by other groups (Ugarte Postigo et al., GCN

40391; Lipunov et al., GCN 40393; Brivio et al., GCN 40395).

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