Structure of Close Binaries. III: Interior Models of Uniformly Rotating Binaries
Abstract
Internal models have been obtained for uniformly rotating synchronous close binary systems using a modified double approximation scheme. We have considered primaries of 10M _{⊙}, 5M _{⊙}, and 2M _{⊙} with mass ratios of 0.0 to 1.0 in steps of 0.1, and some results are given for a 1M _{⊙} primary with a mass ratio of 1.0. A maximum luminosity reduction of 2.3% was found for a 10M _{⊙} primary with a mass ratio of 1.0 and 7.7% for a mass ratio of 0.0. The corresponding values for 5M _{⊙} are 2.0% and 7.0%, and for 2M _{⊙} they are 1.6% and 5.3%, respectively. These values were not found to be sensitive to small changes in composition. The maximum equatorial velocity varies from 399 km s^{1} for 2M _{⊙} to 567 km s^{1} for 10M _{⊙} when the mass ratio is zero, but these velocities decrease by 200 300 km s^{1} if the mass ratio is unity. The effect of gravity darkening on the apparent position of the primary in the theoretical HR diagram was investigated. It was determined that an unresolved close binary of unit mass ratio can lie up to ≃0.9 magnitudes (depending on inclination) above the main sequence, whereas if the effects of distortion are ignored this number is at most 0.75 magnitudes. There seems to be some observational support for the larger value. Two models of the secondaries are given and their dimensions are compared with their critical Roche lobes.
 Publication:

Astrophysics and Space Science
 Pub Date:
 September 1972
 DOI:
 10.1007/BF00645280
 Bibcode:
 1972Ap&SS..18...59N