GCN 45202: EP260723a: Liverpool Telescope likely optical counterpart

R. A. J. Eyles-Ferris (Leicester), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud) and R. L. C. Starling (Leicester) report on behalf of a larger collaboration:

We observed the field of the Einstein Probe fast X-ray transient EP260723a (Zhang et al., GCN 45201) with the 2m Liverpool Telescope on La Palma using the IO:O instrument. We obtained 4x150 s and 5 x150 s exposures in each of the SDSS r’ and g’ filters respectively starting at 2026-07-24 04:35:57 UT, approximately 10.8 hours after the X-ray detection.

We performed image subtraction on the stacked images using reference images from Pan-STARRS and also compared the stacked and reference images manually. In our r-band subtraction and in the stacked image, we identify a new source within the EP/WXT localisation at a position of:

RA 2.97513 (00:11:54.03)
Dec -12.09839 (-12:05:54.2)

We measure an AB magnitude of r = 21.86 +/- 0.11 and a g-band 5-sigma upper limit at the position of g > 22.25. Our photometry is calibrated to PanSTARRS and not corrected for Galactic extinction.

We note the presence of a source in the Legacy Survey consistent with our candidate’s position at a magnitude of r = 23.62 +/- 0.15 and a photometric redshift of 0.91 +/- 0.13. We suggest this could be the host galaxy of EP260723a.