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

TL;DR

This study reports the first detection of line splitting in the optical spectrum of a post-AGB star, revealing details about its circumstellar envelope and impacting chemical abundance calculations.

Contribution

It introduces the first observation of line splitting in a post-AGB star and analyzes its implications for understanding the star's envelope and chemical composition.

Findings

Line splitting detected in the spectrum of V354Lac.

Splitting originates in the star's gas-dust envelope.

Ignoring splitting leads to overestimation of s-process elements.

Abstract

Splitting of the strongest absorption lines with a lower-level excitation potential $\chi<$1eV has been detected for the first time in the optical spectra of the post-AGB star V354Lac obtained with a spectral resolution R=60000 at the 6-m telescope BTA. 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 excess 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 trend in the velocity field in the atmosphere and circumstellar envelope of V354Lac over 15 years of its observations.