Precise dynamical mass measurements of Galactic Binary Cepheids

Long-baseline interferometry achieves an angular resolution down to 0.2 milli-arcseconds, surpassing the capabilities of single-dish telescopes. This method enables the detection of high-contrast, close-in companions of Cepheid stars, which are critical for studying the pulsation and evolution of intermediate-mass stars. A persistent challenge in Cepheid research is the ~10% mass discrepancy between stellar evolution and pulsation models, with the mass remaining a fundamental yet unresolved parameter for decades. Binary Cepheid systems offer the only direct means to refine these models and address this issue. Their close orbits (< 40 mas) and high contrast (> 5 mag in H band) make long-baseline interferometry uniquely suited to detect companions and map their astrometric orbits. This talk presents findings from a long-term observational campaign aimed at determining the dynamical masses and distances of Galactic Cepheids with high precision.