1997PASP..109..848P

Knowledge about the individual components of O-type binaries is difficult to obtain because of the severe line blending present in their spectra. An important new method is Doppler tomography, an iterative scheme that uses a set of orbital phase distributed spectra and both radial velocity curves to reconstruct the individual component spectra (see Bagnuolo, Gies & Wiggs 1992, ApJ, 385, 708). These individual spectra can then be analyzed to determine various physical properties of the stars. The spectral types and luminosity classes obtained provide indicators of the temperatures and gravities. The individual projected rotational velocities can be used to test for rotational synchronization of the orbit or rapid spin-up due to mass transfer. For stars that are cluster members, an estimate of the magnitude difference together with the combined absolute magnitude results in individual luminosity estimates. Finally, it is possible to search for abundance differences due to mass transfer or loss. Here I present results of a program of Doppler tomography of O-binaries observed with the International Ultraviolet Explorer (IUE). I describe cross-correlation methods that use narrow-lined spectral templates to obtain precise radial velocities and orbital velocity curves which are used in the tomography algorithm. I present results for six systems: DH Cep, HD 165052, HD 93403, HD93205, HD 149404, and HD 152248.