Detailed Spectroscopy of Post-AGB Supergiant GSC 04050–02366 in IRAS Z02229+6208 IR Source System

Abstract

—In the optical spectra of the cold post-AGB supergiant GSC $$04050$$–$$02366$$, obtained with the 6‑m BTA telescope with a resolution of $$R \geqslant 60{\kern 1pt} 000$$ on arbitrary dates over $$2019$$–$$2021$$, a radial velocity variability is found: heliocentric $${{V}_{r}}$$ based on the positional measurements of a set of metal absorptions varies from date to date with a standard deviation of $$\Delta {{V}_{r}} \approx 1.4$$ km s^–1 about the average value of $${{V}_{r}} = 24.75$$ km s^–1, which may stem out of the low-amplitude pulsations in the atmosphere. The spectra of the star are purely absorption type, there are no obvious emissions. Intensity variability of most of absorptions and Swan bands of the C₂ molecule was discovered. A slight asymmetry of the H$$\alpha $$ profile is observed at some observation dates. The position of its absorption core varies within $$27.3$$–$$30.6$$ km s^–1. Splitting into two components (or asymmetry) of strong low-excitation absorptions (Y II, Zr II, Ba II, La II, Ce II, Nd II) was found. The position of the long-wavelength component coincides with the position of other photospheric absorptions, which confirms its formation in the atmosphere of the star. The position of the shortwave component is close to the position of the rotational features of Swan bands, which indicates its formation in the circumstellar envelope expanding at a velocity of about $${{V}_{{{\text{exp}}}}} = 16$$ km s^–1.