A SYSTEMATIC survey of the profiles of the Hα line in binary stars, shell stars, Be stars and related peculiar objects is being conducted by us (and G. J. Peters) with the Varo image intensifier attached to the coude spectrograph of the 120-inch telescope and the 24-inch coude auxiliary telescope of the Lick Observatory. Emission at Hα is found to be a more common Phenomenon among the Algol-type eclipsing binaries than was thought before. Usually, but not always, the emission is best observed during the primary minimum when the light of the hotter and brighter component is either greatly reduced or completely occulted. This is in agreement with the models representing the Algol systems as evolved binaries in which mass is still being transferred from the late-type secondary component to the hotter primary star1,2. Although the general picture is fairly clear, the problem remains how the on-flowing material and its angular momentum are distributed among the primary star, the disk revolving around it and a possible envelope enclosing the whole system. The purpose of our survey is to furnish quantitative data on this process.

Outburst in U Cephei

The standard catalogue of variable stars (Kukarkin et al., 1969, 1971, 1974, 1976) recognizes several categories of novae: supernovae (SN), classical novae (N), subdivided where the observations warrant into fast novae (Na), slow novae (Nb), very slow novae (Nc), recurrent novae (Nr), nova-like variables (NZ,), and dwarf novae, including U Geminorum stars (UG) and Z Camelopardalis stars (Z Cam). We exclude supernovae from the present discussion, and summarize the content and interrelationships of the other classes.

Past and Future Novae

The (in many respects, similar) classical Algol-type eclipsing binary systems U Sge and U Cep are studied and compared against a background of photometric evidence, both broadhand and narrowband. Broadband photometry of the primary minimum of U Sge over a four year period fails clearly to confirm Olson's (1982b) finding of radial variations.

Photometry and discussion of the classical Algol systems U Sge and U Cep

Detached close binary systems define the main sequence band satisfactorily, but very little is known about the masses of giants and supergiants. High-dispersion IUE observations promise an improvement, since blue companions are now frequently found to late-type supergiants. The interesting cases of μ Sagittarii and in particular of e Aurigae are discussed in more detail. The barium star abundance anomaly appears now to be due to mass transfer in interacting systems. The symbiotic stars are another type of binary systems containing late-type giants; several possible models for the hotter star and for the type of interaction are discussed. The W Serpentis stars appear to be Algols in the rapid phase of mass transfer, but a possible link relating them to the symbiotics is also indicated. Evidence of hot circumstellar plasmas has now been found in several ordinary Algols; there may exist a smooth transition between very quiescent Algols and the W Serpentis stars. β Lyrae is discussed in the light of new spectrophotometric results.

Evolution of Close Binary Stars: Observational Aspects

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The ALGOLS, Red Spectra, BE Stars, and Even Neutrinos

WE believe that our recent observations of the eclipsing binary U Cephei have implications for the study of the evolution of binary systems and the understanding of novae.

C. D. Scarfe

Papers

Outburst of U Cephei

An outburst of U Cephei.