Characteristics of the cold components of symbiotic stars.

Using the Blackwell-Shallis method the luminosities, temperatures and radii for cool components of symbiotic stars and for a sample of field red giants have been determined by means of infrared photometric observations. It turned out that the cool components of symbiotic stars do not differ from the normal red giants of the asymptotic branch. The masses of cool components of symbiotic stars have been found to be close to 3 M_sun;. The cool components of symbiotic stars do not fill their Roche lobes. About 10 times more carbon stars than the normal value in the vicinity of the sun have been found among the cool components of symbiotic stars.