TITLE:   GCN CIRCULAR
NUMBER:  45831
SUBJECT: EP261006a: LT and NOT discovery of an optical counterpart
DATE:    26/10/07 10:06:31 GMT
FROM:    Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk>

R. A. J. Eyles-Ferris (Leicester), D. B. Malesani (DAWN/NBI and Radboud), G. Corcoran (UCD), J. A. Quirola-Vasquez (Radboud), P. G. Jonker (Radboud), and A. J. Levan (Radboud and Warwick) report on behalf of a larger collaboration:

We observed the field of the fast X-ray transient EP261006a (Lao et al., GCN 45826) with the Liverpool Telescope (LT) and the Nordic Optical Telescope (NOT) equipped with the IO:O and ALFOSC imagers, respectively. Observations started at 2026-10-06 23:26:24 UT (LT) and 2026-10-07 00:26:37 (NOT).

In image subtractions using Pan-STARRS templates, we identify a clear residual spatially consistent with the nucleus of the galaxy Gaia DR3 2587044864659595392. The location is also consistent with the EP-FXT localisation of the transient (GCN 45826). This residual is seen in all our images and we summarise our host-subtracted photometry below.

| t_mid - t0 (hrs) | Telescope | Filter | Exposure time (s) | AB magnitude |
| ------------- | --------- | ------ | ---------------- | ------------ |
| 5.56 | LT | r | 6x150 | 20.22 +/- 0.03 |
| 5.85 | LT | i | 6x150 | 20.78 +/- 0.05 |
| 6.11 | LT | z | 5x150 | 20.59 +/- 0.07 |
| 6.75 | NOT | r | 5x180 | 19.83 +/- 0.03 |

We note the rise in r-band brightness. Our magnitudes are calibrated to Pan-STARRS and not corrected for Galactic extinction. The blue r - i colour and nuclear location of EP261006a are consistent with the tentative classification as a TDE.