2023A&A...677A.154F

We report the discovery of a low-mass totally eclipsing system in the young (age ≃ 28 Myr) open cluster NGC 2232, during an examination of their TESS photometry. The follow-up study of this detached system, TIC 43152097, is based on photometry and high-resolution spectra from the literature and collected by us. The radial velocity of the center of mass and the photospheric lithium abundance of the binary components confirm its membership to NGC 2232. By analyzing the existing photometric and spectroscopic data, we obtain orbital elements and fundamental stellar parameters for the two stars. The primary component of TIC 43152097 is a late F-type dwarf (T_eff = 6070 K), while the lower-mass secondary is a late K-type star (T_eff = 4130 K) that is still in the pre-main-sequence phase. The precise measurements of the radii, masses, and effective temperatures, enabled by the simultaneous solution of light and radial velocity curves, indicate radius inflation for the K-type component, which turns out to be 7-11% larger than that predicted by standard evolutionary models. More sophisticated models incorporating both the inhibition of convective energy transport caused by sub-photospheric magnetic fields and the effects of cool starspots covering a substantial fraction of the stellar surface (30-60%) allow the position of the secondary component to be reproduced in the Hertzsprung-Russell and mass-radius diagrams.