Multiplicity of Luminous Blue Variable Stars

The study of Luminous Blue Variables (LBVs) is critical to understanding the mechanisms behind their recurring S Dor-like outbursts, which can span decades and feature dramatic spectral changes. These outbursts may result from atmospheric instability or interactions with a companion star, but their causes remain poorly understood. Detecting binarity in LBVs through long-term radial velocity (RV) measurements, which can identify orbital motion via shifts in absorption lines, is a promising method. Periodic line shifts and variability can reveal the presence of a companion star. We report on the monitoring of four LBVs and two candidate LBVs (cLBVs), observing high-resolution spectra from 2009 to 2024. Although we do not find a clear periodic RV signal for LBVs MWC 930, P Cyg, or HD 168607, our long-term monitoring campaign previously detected the binarity of cLBV MWC 314 in 2013. For the first time, we detected a periodic signal in the RV data of the cLBV Schulte 12. In addition, in LBV HD 168607, we observed Discrete Absorption Components, indicative of large-scale structures in a rotating wind. These findings advance our understanding of the binary nature of LBVs and their complex outburst behaviors.