[ Previous | Next | ADS ]

EP251102b: LCO and ATLAS observations identify brightening of Gaia DR3 4656768469094327040

ATel #17481; R. A. J. Eyles-Ferris (U. Leicester), J. A. Quirola-Vasquez (Radboud), G. Corcoran (UCD), A. Martin-Carrillo (UCD), J. A. ChacÃ³n (PUC), D. B. Malesani (DAWN/NBI and Radboud), F. E. Bauer (SSI and UTA), P. G. Jonker (Radboud), and A. J. Levan (Radboud and Warwick) report on behalf of a larger collaboration:
on 6 Nov 2025; 11:28 UT
Credential Certification: Rob Eyles-Ferris (raje1@leicester.ac.uk)

Subjects: Optical, Nova, Star

We observed the field of the transient event EP251102b (ATel #17480) detected by the Einstein Probe Wide-field X-ray Telescope (EP-WXT) with the Las Cumbres Observatory (LCO) network. We acquired 6x300s exposures in each of the g, r, i and z bands starting at 2025-11-05 21:31:19.

No new transient source is detected within 20 arcsec of the EP-Follow-up X-ray Telescope (EP-FXT) position of EP251102b (RA=89.8539Â°, Dec = -71.7067Â°) with a limiting magnitude of r > 21.14 (3-sigma). However, the star Gaia DR3 4656768469094327040 (RA=89.8524Â°, Dec = -71.7069Â°) located 2 arcsec from the EP-FXT position has significantly brightened and we measure r = 18.69 +/- 0.05 calibrated against the Legacy catalogue DR10 and not corrected for Galactic extinction. This is 2.10 magnitudes brighter than the r = 20.79 measured in the Legacy DR10 catalogue. A similar brightening is seen in the g, i and z bands and we now measure a much bluer colour of g - r = -0.25 compared to the catalogued g - r = 0.27.

We further examined Gaia DR3 4656768469094327040 using the ATLAS forced photometry server. We find it to have brightened significantly from archival observations, with a current magnitude comparable to that measured in our LCO observations. Gaia DR3 4656768469094327040âs rise appears to start 2025-10-30 in the ATLAS light curve, and there is no evidence of similar variable behaviour since 2022-01-01.

We strongly suggest this brightening is linked to EP251102b and that it could be the emergence of a new nova candidate. We encourage further follow-up observations to determine the nature of this source.