UX Men: Detached Eclipsing Binary as a Benchmark Candidate

We present ultra-precise fundamental parameters for the detached eclipsing binary UX Men based on 31 TESS sectors (∼882 d) and radial velocities from HARPS, FEROS, CORALIE, and UCLES. The light curves were detrended for spot-induced variability and modelled independently with JKTEBOP and ALLESFITTER, while radial velocities were extracted via TODCOR and fitted with a Keplerian orbit. Spectral disentangling yielded individual component spectra analysed with iSpec to determine Teff and [M/H]. Multi-band photometry was used to determine the fluxes, flux ratios and ultimately to measure photometric Teff. We obtain the masses MA = 1.2300±0.0012 M⊙, MB = 1.1946±0.0012 M⊙ and radii RA = 1.3605±0.0031 R⊙, RB = 1.2801±0.0069 R⊙ with sub-percent precision. Uncertainties were found to be dominated by systematic effects coming from (weak) stellar activity. Teff,A = 6302±77, Teff,B = 6292±65 & Metallicity estimates are [M/H]A=0.02±0.13 dex and [M/H]B=0.07±0.10 dex. Isochrone fitting yields a consistent age of τ = 2.75±0.13 Gyr. The system exhibits a ∼ 673-day periodicity in eclipse-timing variations, likely due to stellar activity, with no evidence for a third body. Results are independent of the modelling code used, but without proper treatment of activity-induced systematics the uncertainties would be underestimated. UX Men is a high-precision benchmark binary providing stringent tests of stellar models and a robust calibration source for PLATO. Expanding the sample of well-characterised detached eclipsing binaries will strengthen the empirical foundations for stellar physics and the calibration of future photometric missions.

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