Near-infrared spectral classification of symbiotic stars.

Near-infrared spectra of 16 symbiotic stars and 29 G, K and M standard stars are presented. The spectrograms are used to classify the cool components in symbiotic stars. The equivalent width of the CN band feature at (7916+7941) Å is demonstrated to be a quantitative luminosity indicator for classes III to I in the (single) M0 to M3 standard stars. Six of the observed symbiotic stars have temperature classes within this range and the criterium is applied to their spectrograms. Accordingly, four of the late-type components are normal giants, while the nature of two systems remains ambiguous. The results are discussed in the light of presently proposed interacting binary models for symbiotic stars.