TITLE: GCN CIRCULAR NUMBER: 38921 SUBJECT: EP250109b: optical upper limits with the Liverpool Telescope DATE: 25/01/13 12:00:00 GMT FROM: Amit Kumar at Royal Holloway - UoL/ U of Warwick, UK amitkundu515@gmail.com

A. Kumar (RHUL), N. C. Sun (UCAS), J. R. Maund (RHUL), W. X. Li, Y. N. Wang (NAOC), and K. Wiersema (Herts) report:

We observed the field of EP-WXT-detected transient EP250109b (Cheng et al., ATel #16974) using the IO:O imager on the 2m Liverpool Telescope. Observations were carried out between 2025-01-10 UT 23:39:42 and 2025-01-11 UT 01:02:34, corresponding to ~1.65 and ~1.71 days post-trigger, respectively, in the g, r, and z bands.

In each band, 3×600s exposures were obtained. However, the g- and z-band frames were affected by trailing and are unsuitable for analysis.

In the stacked r-band image (at ~1.67 days post-trigger), no new, uncatalogued source was detected within the EP-FXT localization uncertainty region (Cheng et al., ATel #16974), down to a limiting magnitude of r > 21.8 (AB).

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