Observed Properties of Mass Loss in Symbiotic Binaries

Both the red giants and the Mira variables in symbiotic systems have systematically higher mass-loss rates than do typical galactic giants and Miras, which suggests that only very evolved giants, and so those with highest mass-loss rates, can support symbiotic behaviour in widely separated binary systems. They often show a flattened mass-loss geometry due to an intrinsically inhomogeneous mass loss and/or tidal interactions between the binary components. The main body of a symbiotic nebula is thus formed from material lost in the giant wind, while the hot component is responsible for its ionization and excitation. In addition, the fast wind and/or jet ejection from the hot component, whenever occur, give rise to the complex, often bipolar, shape of symbiotic nebulae. Observations of resolved nebulae also suggest that the binary geometry and nebular structure are aligned but the bipolar outflow may be not orthogonal to the orbital plane in all cases.