UX Men: Detached eclipsing binary as a benchmark candidate

Abstract

Detached eclipsing binaries (DEBs) provide model‑independent measurements of stellar masses and radii, which are essential for testing stellar‑evolution models and calibrating space‑based photometric missions. We aim to deliver ultra-precise fundamental parameters for the DEB UX Men and to assess its suitability as a benchmark for upcoming missions such as . We evaluate the temporal stability of the photometric solutions and the way intrinsic stellar variability and instrumental systematics affect the derived parameters. PLATO We analysed 31 TESS sectors ( 882 d) with the lightkurve package, and detrended spot‑induced variability. Light‑curve modelling was performed independently with jktebop and allesfitter . Radial velocities from HARPS (HAM/EGGS), FEROS, CORALIE, and UCLES were extracted via todcor and fitted with a Keplerian orbit. Spectral disentangling (5350–5800 Å) yielded individual component spectra, which were processed with ispec to determine , mathrm M/H , and micro‑ and macroturbulence. Eclipse‑timing variations were examined through O-C diagrams. We also used multi-band photometry to determine the fluxes, flux ratios, and ultimately, to measure the photometric . We obtained masses of M_̊m A = 1.2300 M_⊙, M_̊m B = 1.1946 _ 0.0012 M_⊙ and radii of R_̊m A = 1.3605 = 0.02 $ dex and $ R_⊙, R_̊m B = 1.2801 _ R_⊙, with a sub-percent precision. Uncertainties were found to be dominated by systematic effects coming from (weak) stellar activity. The metallicity estimates are $ M/H ̊m A 0.13 M/H ̊m B = 0.07 $ dex. An isochrone fitting yielded a consistent age of τ = 2.75 0.10 Gyr. The system exhibits a 673-day periodicity in eclipse‑timing variations, likely due to stellar activity, with no evidence of a third body. UX Men is a high‑precision benchmark binary, providing stringent tests of stellar models and a robust calibration source for PLATO ’s determination of stellar and exoplanet properties. We found no dependence between the results and the specific code that was employed. However, without a proper treatment of systematics caused by activity, the uncertainties would end up underestimated. Expanding the sample of similarly well‑characterised DEBs will further strengthen the empirical foundation for stellar physics and improve the calibration of future photometric missions.