A study of some early type close binary stars

Abstract

A study of spectroscopic and photometric material for three binaries has supplied additional evidence regarding dynamical interaction between their components. 1. Beta Scorpii: A new orbit of the primary confirms the apsidal motion found by earlier workers. The velocity for the secondary is 40 km/sec positive with respect to that of the primary; at least part of the difference is real. λ 4471 of He I and λ 4553 of Si III are about twice as strong when the secondary is approaching as when the secondary is receding. Hγ shows smaller changes in the opposite direction. Changes in line intensities and the difference between γ₁and γ₂ are attributed to gaseous matter projected against the approaching side of the secondary. Measured difference in the magnitudes of the two components indicates that the secondary is overluminous. 2. HD 47129: Combining new observations with the old, a correct period of 14.3961 days is , and a new orbit of the primary is obtained. The measures of secondary lines show large scatter, difference in γ₁and γ₂, and a velocity amplitude smaller than the primary. Systematic changes in velocity- curves and line intensities from one epoch to the next are also noted. At phases around 7.2 days, the secondary lines are stronger by 3040 per cent; hydrogen lines in the primary spectrum are fuzzy and have negative velocities with respect to the mean for all lines. The spectral types of the two components are alike, but the strength of the red He I lines indicates a strong red continuum for the secondary. Analysis of the shell lines gives a mean distance of the circumstellar envelope from the center of the primary equal to six times the radius of the star. Variations in the number of absorbing atoms in the envelope in different directions and from cycle to cycle are indicated. The electron temperature of the shell is 24000°, the electron density is 1.7 × 10¹¹/cc, and the mass density is about 3.3 × 10^-13 gm/cc. The He/H abundance ratio in the primary is normal. The distance of the star is about 1140 parsecs. 3. AO Cassiopeiae: Comparison of a new spectroscopic orbit with earlier orbits gives definitive values of γ₁ = -31.1 ± 0.07 km/sec and e = 0.035 ± 0.004. K₁ and K₂ seem to vary from epoch to epoch. Apsidal motion with a period of 70 years is found. Observations of the secondary are widely scattered, but they do not indicate any real difference between the γ velocities of the two components. The velocity amplitude of the secondary is smaller than that of the primary. Photometric light-curves in yellow, blue, and ultraviolet colors show asymmetries and negative reflection effects. The observed primary minimum is shifted by -0.67 day with respect to the computed phases. Irregular fluctuations of light of the order of 0.03 mag. are superposed on the smooth variation of the light of the primary.