Detection of heavy-metal lines in the spectrum of the circumstellar envelope of a post-AGB star

Splitting of the strongest absorption lines with a lower-level excitation potential χ _low < 1 eV has been detected for the first time in the optical spectra of the post-AGB star V354 Lac obtained with a spectral resolution R = 60 000 at the 6-m BTA telescope. Analysis of the kinematics shows that the short-wavelength component of the split line originates in the star’s thick gas-dust envelope. Disregarding the splitting of strong lines when the chemical composition is calculated leads to overestimated overabundances of s-process elements (Ba, La, Ce, Nd) in the stellar atmosphere. The profiles of strong absorption lines have been found to be variable. The available radial-velocity data suggest the absence of any changes in the velocity field in the atmosphere and circumstellar envelope of V354 Lac over 15 years of its observations.