Detection of six massive contact binaries with tertiary component candidates in the Small Magellanic Cloud.

This article focuses on the study of massive early-type contact binary stars in the Small Magellanic Cloud (SMC), a low-metallicity environment, to investigate their period changes and multiplicity. Using photometric data from the Optical Gravitational Lensing Experiment (OGLE) and the Transiting Exoplanet Survey Satellite (TESS), six such binaries exhibiting periodic period variations were analyzed via the Wilson–Devinney (WD) method and O–C (observed minus calculated) light-curve analysis. The period changes are interpreted as caused by the light-travel time effect due to third bodies orbiting these binaries, with derived third-body orbital periods ranging from 6.41 to 24.65 years and minimum masses between 0.31 and 4.11 solar masses. The study finds a high fraction of companions among massive contact binaries in the SMC, supporting a correlation between stellar multiplicity and mass, and suggests that additional components may significantly influence the evolution of massive close binaries. These results provide observational constraints for binary evolution models in different galactic environments and highlight the need for further observations to explore metallicity effects on massive binary formation and evolution.