Orbits of Detached Main-Sequence Eclipsing Binaries of Types Late F to K. III. AD Bootis and du Leonis

In this third paper of a series, spectroscopic orbits are obtained for the main-sequence eclipsing binaries AD Boo (P = 2.07 days, F6 + G0) and DU Leo (P = 1.37 days, G0:). The available photometry of AD Boo may be adequate, but a second photometric study, at Copenhagen, is in the offing. This binary will soon be unique in having three independent spectroscopic studies of high quality, providing stringent tests of possible systematic differences between observational sets. The available photometry of DU Leo provides marginally useful coverage of the light curve. The components of AD Boo are sufficiently different in mass and radius to provide a good test of interior models. They lie above the mass range in which difficulties of interpretation were encountered in the previous paper in this series. The components of DU Leo are nearly equal in mass and radius. According to extant evolutionary models, the age of the system appears comparable to that of the Galaxy. The roughly determined spatial velocity is also suggestive of membership in an older population. Discrepancies among spectral type criteria may imply a nonstandard chemical composition.