Observations of ζ Aurigae Stars and Their Interpretation

A summary of information on the extended atmosphere of the K component coming from three eclipsing binaries consisting of a K supergiant and a main sequence B star. Various anomalies exist: (1) Discrepancy between electron density and metallic density inferred from observations, noting that the electrons should come from the metals. This suggests a cloud structure in the atmosphere. (2) Anomalous excitation temperatures and populations of the second quantum level of hydrogen suggests a solar-chromosphere type behavior for these K atmospheres. (3) Significant changes in the profiles of the Ca + lines from one eclipse to another. The necessity to distinguish between effects coming from radiation of the B star on the K atmosphere and chromosphericlike effects is emphasized.