GCN Circular 45831

Subject

EP261006a: LT and NOT discovery of an optical counterpart

Event

EP261006a

Date

2026-10-07T10:06:31Z (14 hours ago)

From

Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk>

Via

Web form

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.