A photometric and spectroscopic study of eight semi-detached eclipsing binaries

Context. Semi-detached eclipsing binaries offer an exceptional opportunity to validate the evolutionary models of interacting binaries. This entails determining the absolute parameters and evaluating the evolutionary status of the binary components through simultaneous analysis of both light and radial velocity curves. The Transiting Exoplanet Survey Satellite (TESS) provides high-precision light curves, while the Large Sky Area Multi-Object Fibre Spectroscopic Telescope Medium-Resolution spectroscopic Survey (LAMOST MRS) offers multi-epoch observations. The combination of these data enhances the accuracy of deriving precise parameters for binary systems. Aims. The aim of this study is to estimate the absolute parameters of semi-detached binary components, offer potential explanations for their evolutionary status, and investigate long-term variations in orbital periods to explore their underlying causes. Methods. By cross-matching the eclipsing binary catalogue from TESS with that from LAMOST MRS, semi-detached eclipsing binaries with radial velocities spanning more than 0.3 phases were authenticated. The absolute parameters for these systems were determined by simultaneous modelling of light curves and radial velocities using the Wilson-Devinney programme. Additionally, the secular orbital variations were further analysed using O–C curves. Results. Eight semi-detached eclipsing binaries have been identified. Among them, seven contain primary stars situated within the main-sequence band, while their secondaries are all in evolved stages. This suggests that these systems likely originated as detached binaries and have undergone a reversal of the mass ratio. However, TIC 428257299 is an exception where the primary is Roche lobe-filling, and its secondary has experienced mass loss events. Additionally, TIC 8677671 and TIC 318217844 demonstrate secular cyclical variations in orbital periods. Specifically, for TIC 8677671, the cyclical change could result from magnetic activity or a third body that is likely to be compact, with a mass of at least 2.97 M ⊙ .