Doppler Tomography of the Massive Compact Binary Stars in the Multiple Star Systems δ Orionis and HD 206267
Publications of the Astronomical Society of the Pacific
Cross-correlation techniques were applied separately to 60 International Ultraviolet Exporer (IUE) ultraviolet spectra and 20 ground-based optical spectra of the massive close binary star in the triple system d Orionis A, producing the first double-lined spectroscopic orbital elements for this binary. The resulting masses are and 3 m sin i p 8.7 ע 1.4 M 1 , . Existing photometric orbits and 3 m sin i p 4.4 ע 0.3 M 2 , Hipparcos photometry limit the central binary's orbital inclination to
... l inclination to the range , resulting in spectroscopic 67Њ-77Њ masses of, at most, and (Harvin m p 11.2 M m p 5.6 M 1 , 2 , et al. 2002et al. , ApJ, 565, 1216. These masses are shockingly low-about one-third of the masses that would be expected based on the nonrotating stellar models of Schaller (1992, A&AS, 96, 269), given the component MK types. These masses are also less than one-half of those predicted by the more recent rotating stellar models of Meynet & Maeder (2000, A&A, 361, 101). Subsequent cross-correlation analysis of the 36 IUE ultraviolet spectra of the massive close binary star in the triple system HD 206267 A found masses of 3 m sin i p 28.0 ע 1 and (J. Harvin et al. 2004, 3 1.8 M m sin i p 15.3 ע 1.5 M , 2 , in preparation) for that binary, in general agreement with both the masses expected from evolutionary models and the masses found by Burkholder et al. (1997, ApJ, 490, 328), based on optical spectra. Hipparcos detected photometric variations in HD 206267 A, but they could not be definitely classified as eclipses, constraining only the upper limit of HD 206267 A's orbital inclination. In view of the magnitude of the mass discrepancy found, the components of the central binary in d Orionis A may turn out to be post-Roche Lobe overflow objects of the very early case A variety. In this scenario, repeated close passes by the tertiary star would have robbed the central binary of its orbital energy, bringing the components into Roche Lobe overflow and resulting in two stars that are overluminous for their masses by a factor of 10, but somewhat underluminous for their respective MK types. The ultraviolet spectra and the optical He i line pro-l6678 files of the components of d Orionis A and the ultraviolet spectra of the components of HD 206267 A were reconstructed using a version of the Doppler tomography algorithm from Bagnuolo et al. (1994, ApJ, 423, 446), based on the new radial velocity orbits described above. Analysis of the reconstructed spectra revealed the component stars' spectral morphology, rotational velocities, and relative flux contributions.