Spectroscopic and Photometric Analysis of the O‐Type Binary V1182 Aquilae: A Close Eclipsing System with a Luminous Third Body

We obtained high-resolution spectroscopy and UBV photometry of the O-type eclipsing binary V1182 Aql. In the spectra lines of a third component were found; the presence of third light is also supported by the solution of the light curves. New masses for both components of the binary were derived: M1 = 31.0 and M2 = 16.6 M☉. These values differ considerably from those given by Bell et al., which were obtained by neglecting the presence of a third body. With Teff ~ 43,000 K the primary component is much hotter than expected for the previously assumed spectral type O8. Its classification has to be revised to O5.5, which makes V1182 Aql probably the earliest eclipsing binary in the Galaxy. The mass of the primary is smaller than suggested by evolutionary models, while the secondary parameters agree with a position close to the zero-age main sequence (ZAMS). The third body, which manifests itself by strong lines in the optical spectrum and by a third light contribution of ~17% as deduced from the light curve solution might be detectable by interferometric measurements.