Tomographic Separation of Composite Spectra. VII. The Physical Properties of the Massive Triple System HD 135240 (δ Circini)

We present the results of a radial velocity study of the massive, double-lined, O binary HD 135240 based primarily on UV spectroscopy from the International Ultraviolet Explorer. Cross-correlation methods indicate the presence of a third stationary spectral line component which indicates that the system is a triple consisting of a central 3.9 day close binary with a distant companion. We measured radial velocities from the cross-correlation functions after removal of the third component, and we combined these with velocities obtained from Hα spectroscopy to reassess the orbital elements. We applied a Doppler tomography algorithm to reconstruct the individual UV spectra of all three stars, and we determine spectral classifications of O7 III-V, O9.5 V, and B0.5 V for the primary, secondary, and tertiary, respectively, using UV criteria defined by Penny, Gies, & Bagnuolo. We compare these reconstructed spectra to standard single-star spectra to find the UV flux ratios of the components (F₂/F₁ = 0.239 ± 0.022, and F₃/F₁ = 0.179 ± 0.021). Hipparcos photometry reveals that the central pair is an eclipsing binary, and we present the first model fit of the light curve from which we derive an orbital inclination, i = 74° ± 3°. This analysis indicates that neither star is currently experiencing Roche lobe overflow. We place the individual components in the theoretical H-R diagram, and we show that the masses derived from the combined spectroscopic and photometric analysis (M_p/M_☉ = 21.6 ± 2.0 and M_s/M_☉ = 12.4 ± 1.0) are significantly lower than those computed from evolutionary tracks for single stars.