The origin of sinusoidal brightness variations in F- to O-type stars through radial velocities

Stellar variability may originate from various phenomena such as binarity, pulsations, or rotation. These mechanisms can induce flux variations of similar magnitudes, shapes, and periods. We aim to determine mechanisms responsible for the sinusoidal variations in main-sequence stars hotter than 6500,K. We conducted our analysis using TESS long-cadence data complemented with high-resolution spectra from three spectrographs. From the initial sample of almost 46,000 objects, we selected 35 targets for spectroscopic follow-up. The comparison of light curves and radial-velocity curves allowed for the robust classification of these targets. Among the 35 selected objects, 18 displayed variability, suggesting the presence of a companion (including the discovery of seven new binary systems and one candidate for a triple-star system), one was identified as a new pulsator, nine as new candidates for spotted stars, and seven objects had uncertain classification. Our analysis shows that at least half of randomly selected stars with sinusoidal brightness variations are binaries. The presented results illustrate the need for an individual approach to stellar classification, especially in cases where the photometric data alone is insufficient for determining the underlying phenomena behind the observed variations.