The double-lined spectroscopic binary psi Orionis.

The spectroscopic orbits for both components of Psi Ori are determined from high-dispersion spectrograms measured by cross-correlation techniques. The orbital elements are listed in a table. From spectrophotometric measurements, the spectral types and luminosity classes are found to be B1 III for the primary star and B2 V for the secondary star, with mean projected rotational velocities of 95 km/s and 75 km/s, respectively. A luminosity ratio of 4.5, determined from the ratio of line strengths corrected for spectral type and corresponding to a difference of 1.6 m in the blue region of the spectrum, is found. The spectroscopic parallax which is obtained corresponds to a distance of 640 + or - 30 parsecs.