The cool components of symbiotic stars. I - Optical spectral types

The authors present an analysis of prominent absorption features on red (λλ5500 - 8600 Å) spectra of symbiotic stars. The depths of TiO and VO bands appear to be correlated with the brightness of the system; this behavior is probably the result of the secondary star heating the outer atmosphere of the cool giant. The authors have derived new spectral types and luminosity classes for the cool components of symbiotics, and these classifications suggest a division into semidetached systems and detached systems. Mass-loss rates for detached symbiotics which do not contain Mira variables remain higher than those estimated for single red giants of the same spectral type, suggesting that the presence of a binary companion enhances mass loss in these objects.