The low-mass companions in eclipsing binaries with F/G primaries: <i>TESS</i> photometry and NIRPS/HARPS spectroscopy of eight eclipsing binaries with M-dwarfs secondaries

ABSTRACT Binary systems containing M-dwarf components alongside F/G-type primaries are key to testing and improving stellar evolution models. The mass of these stars, together with their small radii and low temperatures – which contribute for less than 2 per cent of the total flux at optical wavelengths – renders it challenging to identify them in orbit around host stars. These companions are suitable for calibrating and testing stellar models, as well as data analysis algorithms employed by the Near-InfraRed Planet Searcher (NIRPS)/High Accuracy Radial Velocity Planet Searcher spectroscopic surveys and discovered mainly by Transiting Exoplanet Survey Satellite. The light curves generally display clear total eclipses, exhibiting minimal activity-related variability in the overall light curves. We analysed near-infrared spectra gathered from the NIRPS survey to determine the spectroscopic orbit for systems. In this way, we examined different theoretical relationships related to M dwarfs by estimating eight high-precision, model-independent masses, and radii for M dwarfs, reaching an accuracy of over 4 per cent. No discernible trend is observed between overinflation and either mass or radius. Furthermore, the radii of M dwarfs seem to align more closely with predictions, although they display a similar degree of measurement scatter as M dwarfs previously studied in the optical region. Our sample provides eight significant data points for the mass–radius diagram of convective M dwarfs, which can be used for further research into radius inflation.