New Spectroscopic Observations of the Post-AGB Star V354Lac=IRAS22272+5435

Abstract

The strongest absorption features with the lower-level excitation potentials ${\chi }_{\mathrm{low}}<1$ eV are found to be split in the high-resolution optical spectra of the post-AGB star V354 Lac taken in 2007--2008. Main parameters, T${}_{eff}$=5650 K, $\log g$=0.2, ${\xi }_t$=5.0 km/s, and the abundances of 22 chemical elements in the star's atmosphere are found. The overabundance of the $s$-process chemical elements (Ba, La, Ce, Nd) in the star's atmosphere is partly due to the splitting of strong lines of the ions of these metals. The peculiarities of the spectrum in the wavelength interval containing the LiI $\lambda$ 6707 Å line can be naturally explained only by taking the overabundances of the CeII and SmII heavy-metal ions into account. The best agreement with the synthetic spectrum is achieved assuming $\epsilon$(LiI)=2.0, $\epsilon$(CeII)=3.2, and $\epsilon$(SmII)=2.7. The velocity field both in the atmosphere and in the circumstellar envelope of V354 Lac remained stationary throughout the last 15 years of our observations.

16 pages, 6 figures, 2 tables

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