IR-source IRAS20508+2011: spectral variability of the central star

Abstract

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

arXiv comment26 pages, 4 PS-figures, 4 tables, uses A&A style

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• High-latitude supergiant V5112 Sgr: enrichment of the envelope with heavy s-process metals
• New in the optical spectrum and kinematic state of the atmosphere of the variable V1027\,Cyg (= IRAS 20004+2955)
• High-resolution optical spectroscopy of the post-AGB supergiant V340 Ser (=IRAS 17279$-$1119)