UX Men: Detached Eclipsing Binary as a Benchmark Candidate

Abstract

We present ultra-precise fundamental parameters for the detached eclipsing binary UX Men based on 31 TESS sectors ($\sim$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 $T_{\mathrm{eff}}$ and $[M/H]$. Multi-band photometry was used to determine the fluxes, flux ratios and ultimately to measure photometric $T_{\mathrm{eff}}$. We obtain the masses $M_{\mathrm{A}}$ = $1.2300\pm 0.0012$ M${}_{\odot }$, $M_{\mathrm{B}}$ = $1.1946\pm 0.0012$ M${}_{\odot }$ and radii $R_{\mathrm{A}}$ = $1.3605\pm 0.0031$ R${}_{\odot }$, $R_{\mathrm{B}}$ = $1.2801\pm 0.0069$ R${}_{\odot }$ with sub-percent precision. Uncertainties were found to be dominated by systematic effects coming from (weak) stellar activity. $T_{\mathrm{eff},\mathrm{A}}$ = $6302\pm 77$, $T_{\mathrm{eff},\mathrm{B}}$ = $6292\pm 65$ \& Metallicity estimates are $[M/H{]}_{\mathrm{A}}=0.02\pm 0.13$ dex and $[M/H{]}_{\mathrm{B}}=0.07\pm 0.10$ dex. Isochrone fitting yields a consistent age of $\tau$ = $2.75\pm 0.13$ Gyr. The system exhibits a $\sim$ 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

19 pages and 12 figures. Accepted for publication in Astronomy & Astrophysics