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High spectral resolution echelle spectroscopy of supergiants at the post-ABG
stage resulted in the formation of a sample of these objects possessing a
high infrared excess, an emission at 21 μm, and also large overabundances
of carbon and heavy metals, synthesized by the s-process at the preceding
AGB stage.
As a result of the spectroscopic monitoring carried out at the 6-m BTA
telescope, a previously unknown (for this evolutionary stage) phenomenon
was discovered in the optical spectra of selected objects of this
sample - an asymmetry of the metal lines, to the extent of splitting
of the strongest low-excitation absorption lines. The effect is strongest
in the most evolved, high-latitude supergiant V5112 Sgr=IRAS19500-1709,
which has an extended structured envelope (Figs.1 and 2). In the optical
spectrum of this object, the BaII ion lines are split into three components
(Figs.3 and 4).
An analysis of the velocity field in the extended atmosphere and envelope
of V5112 Sgr resulted in a conclusion that the short-wavelength components
of the split BaII absorptions are formed in the structured circumstellar
envelope. Thus, we discovered for the first time the enrichment of the
stellar envelope with heavy metals produced at the AGB stage.
Published:
V.G.Klochkova. Detection of heavy-metal lines in the spectrum of the
circumstellar envelope of a post-AGB star. Astronomy Letters, 2009,
35, No.7, pp.457-465.
V.G.Klochkova. High-latitude supergiant V5112 Sgr: Enrichment of the
envelope with heavy s-process metals. Astronomy Letters, 2013, 39,
No.11, pp.765-775
Contact - Klochkova V.G.
Fig.3.
The BaII 4554 A line, split into 3 components, in the spectrum of V5112Sgr.
The FeII 4556 А line with a similar intensity is not split
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Fig.4.
The variability of the profile of the split BaII 4934 Å line in
the spectrum of V5112Sgr. The vertical arrows show the envelope components.
The dashed line denotes the systemic velocity
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Fig.1.
Asymmetric envelope of the source IRAS19500-1709 in the near-IR range
Fig.2.
Asymmetric envelope of the source IRAS19500-1709 in the far-IR range
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