Abstract
Evolutionary and distance estimation issues for eclipsing binaries (EBs) are examined in the context of spin-off from gravitational lens surveys and the GAIA mission. The OGLE survey shows a major deficiency of normal Algol type binaries in the Small Magellanic Cloud. Statistical analysis coupled with further observing will be needed to decide if the Algol shortfall is an evolutionary effect connected with low metallicity or is only apparent. Distances estimated for EBs are directly physical, with no need for calibration via nearby examples with known distances (EB distance indicators are therefore not standard candles, contrary to common usage of the name). Only the best examples will be needed for distances, given the enormous numbers of EBs expected from GAIA, so one can be very selective. Accordingly the relative merits of detached (DB), semi-detached (SD), and overcontact (OC) EBs are discussed, with emphasis on under-recognized advantages of SDs and OCs. Included are considerations of orbital eccentricity, morphology, photometric mass ratios, observing efficiency, aliasing of radii, and practicality.
Published Version
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