TITLE:   GCN CIRCULAR
NUMBER:  43553
SUBJECT: EP260128a: Liverpool Telescope optical observations and possible counterpart
DATE:    26/01/29 09:33:37 GMT
FROM:    Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk>

R. A. J. Eyles-Ferris and R. L. C. Starling (Leicester) report on behalf of a larger collaboration:

We observed the field of EP260128a (Zhou et al., GCN 43549) with the 2m Liverpool Telescope on La Palma using the IO:O instrument. We obtained 6x150s exposures in each of the SDSS r’ and SDSS g’ filters starting at 2026-01-28 23:56:39 UT, approximately 16.6 minutes after the X-ray detection.

We performed image subtraction on the stacked images using reference images from Pan-STARRS and Legacy DR11 and also compared the stacked and reference images manually. In the r’ stack and within the EP/FXT localisation, we tentatively identify a low significance source at a position

RA 08:33:18.17 (128.32569 deg)
Dec -10:16:19.3 (-10.27202 deg)

The source is detected to ~2.6-sigma and we measure r’ = 22.92 +/- 0.38. The source is not visible in the g’ stack (started ~18 minutes later).

We derive 3-sigma upper limits for our stacked images of r’ > 22.8 and g’ > 22.5 with AB photometry calibrated to Pan-STARRS and not corrected for Galactic extinction.