Introduction & Overview to Symposium 240: Binary Stars as Critical Tools and Tests in Contemporary Astrophysics
The new and exciting developments in the studies of binary and multiple stars are discussed. An overview is given of the major topics and themes of IAU Symposium 240. These include new observing techniques and reduction methods for the study of binary and multiple star systems as well as the important astrophysical quantities that can be uncovered from such observations. Emphasis is given to new developments that include results from high resolution interferometry and high precision photometry and spectroscopy as well as results from multi-wavelength and panoramic photometry programs of binaries both inside and outside the Galaxy. Also discussed are the uses of binary and multiple star systems as critical tools for the study and tests of many important aspects of modern astrophysics. To give a few examples, binary and multiple stars are playing major roles in (1) testing stellar evolution theory (by providing fundamental stellar quantities), (2) cosmology (standard candles for improving the cosmic distance scale), (3) probes of galactic structure (e.g. from fragile binaries), as well as (4) providing tests of stellar structure and General Relativity (apsidal motion studies). Also binary systems with accreting degenerate components (like CVs and XBs) provide miniature laboratories of the study of accretion processes found in AGN galaxies. These are but a few out a very large number of exciting topics discussed at the symposium. Also discussed are the new classes of binary stars that include binary systems with planetary and brown dwarf components. The future of the study of binary stars also will be briefly addressed and discussions of new opportunities and the challenges with upcoming new instrumentation, telescopes and space missions will be be noted. For example, one major (but very exciting) problem will be how get the most scientific rewards from the huge number (millions) of additional binaries expected to be discovered from wide field synoptic surveys both from the ground and from space. This work was, in part, sponsored by Grants from the US National Science Foundation and NASA which we gratefully acknowledge. Also I would like to acknowledge travel support from a grant from the NSF to the AAS.