Why we Study Binary Stars

Harold A. McAlister (Georgia State University)

Abstract:

The study of binary stars provides information about the fundamental properties of stars; most particularly, their mass which, following Vogt's Theorem is the single most important parameter in determining the entire course of evolution of a star. Because of the coeval nature of the components of binaries, they also serve as tests of stellar evolution models. The statistics of binary star frequency across age and spectral type also reveal a great deal about the circumstances of star formation. While there are more than 100,000 binary star systems known, only a very small fraction of these have yielded their basic properties to astronomers. This is because no single method of observation is sufficient to extract the masses of the components of a given binary, and there has typically been little overlap in the selection effects inherent in the basic methods of observations (visual, spectroscopic, photometric). Interferometry is eliminating this non-overlap through the resolution of spectroscopic binaries, where, in the case of a double-lined SB, the individual masses and the distance to the system can be directly determined. Thus we can anticipate a very significant increase during coming years in the number of accurately determined stellar masses.

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References:

• Binary and Multiple Systems of Stars
  A. H. Batten (Pergamon 1973)

• Double Stars
  W. D. Heintz (Reidel 1978)

• Principles of Astrometry
  P. van de Kamp (Freeman 1967)

• The Binary Stars
  R. G. Aitken
  (this class has had several reprintings by Dover)

• Complementary Approaches to Double and Multiple Star Research
  Proceedings of IAU Colloquium 135
  edited by H.A. McAlister and W.I. Hartkopf
  Astronomical Society of the Pacific Conference Series Volume 32, (ASP : San Francisco), 598 pages, 1992.

• Visual Double Star: Formation, Dynamics and Evolutionary Tracks
  edited by J.S. Docobo, A. Elipe and H.A. McAlister
  (Kluwer Academic Publishers: Dordrecht), 508 pages, 1997.