TITLE: GCN CIRCULAR NUMBER: 40135 SUBJECT: GRB 250407A: Continued KAIT/Nickel optical observations DATE: 25/04/11 07:26:26 GMT FROM: Weikang Zheng at UC Berkeley weikang@berkeley.edu

Asia deGraw, Gracelynn Jost, WeiKang Zheng and Alexei V. Filippenko

(UC Berkeley) report on behalf of the KAIT GRB team:

The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at

Lick Observatory, continued the observation of GRB 250407A optical

afterglow (Zheng et al., GCN 40116; Ducoin et. al, GCN 40117;

Pérez-Fournon et. al, GCN 40125; Pankov et al., GCN 40133) at

03:35 UT, Apr. 09, namely ~1.55 days after burst. A set of clear

(roughly R) filter images were obtained. Compared to our earlier

observations (Zheng et al., GCN 40116), the reported afterglow had

faded to ~20.8 +/- 0.3 mag (Vega) measured in our coadd image.

Additional R band images with 600sx5 exposure were obtained with the

1-m Nickel telescopes located at Lick observatory, starting at ~1.55

days after burst. We measure the brightness of R ~ 21.0 +/- 0.2 mag

(Vega), similar to the R band magnitude reported by Pankov et al.

(GCN 40133) at a slightly later epoch (1.98 days), suggesting that

this might be the host galaxy of GRB 250407A as suggested by Ducoin

et. al, GCN 40117).

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