  Over the five years of high-resolution spectroscopy of the cool star
identified with the IR source IRAS20508+2011, the photospheric radial velocity
variability Vr=15-30km/s is detected. In the same time, the Halpha profile
varied from an intense bell-shaped emission line with a small absorption to
2-peaked emission with a central absorption feature below the continuum level.
The NaD doublet lines shown a complex profile with broad (FWHM \approx 120km/s)
emission and photospheric absorption, as well as an interstellar component. We
used model atmospheres to determine the physical parameters and chemical
composition of the star's atmosphere: Te=4800K, log g=1.5, [Fe/H]=-0.36, [O/Fe]
=+1.79 (with the ratio [C/O]=-0.9). The totality of the parameters suggests
that the optical component of IRAS20508+2011 is an O-rich AGB star with
luminosity Mv
