TITLE: GCN CIRCULAR NUMBER: 39401 SUBJECT: EP250220a: Liverpool Telescope optical upper limits DATE: 25/02/21 09:31:44 GMT FROM: Rob Eyles-Ferris at U of Leicester raje1@leicester.ac.uk
R. A. J. Eyles-Ferris, P. T. O’Brien and R. L. C. Starling (U of Leicester) report:
We observed the field of the X-ray transient EP250220a (Wang et al., GCN 39387) with the 2m Liverpool Telescope using the IO:O instrument. We obtained 4x100s exposures in the SDSS g’ filter starting at 2025-02-20 22:14:10 UT and 6x100s exposures in the SDSS r’ filter starting at 2025-02-20 22:22:20 UT, approximately 20 hours after the X-ray detection.
We performed image subtraction on the stacked images using reference images from Pan-STARRS and, due to the crowded field and therefore extensive subtraction artefacts, compared the stacked and reference images manually. Consistent with Zhang et al. (GCN 39393) and Fan et al. (GCN 39400), we identify no new sources within the error region of the EP/FXT candidate. We derive 3-sigma upper limits of g’ > 21.5 and r’ > 21.8 with photometry calibrated to Pan-STARRS and not corrected for Galactic extinction.
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