Astronomy and Astrophysics – Astronomy
Scientific paper
Oct 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996mnras.282.1171z&link_type=abstract
Monthly Notices of the Royal Astronomical Society, Volume 282, Issue 4, pp. 1171-1180.
Astronomy and Astrophysics
Astronomy
26
Stars: Abundances, Stars: Agb And Post-Agb, Stars: Atmospheres, Stars: Individual: Hd 179821=Iras 19114+0002, Supergiants
Scientific paper
A high-resolution and signal-to-noise ratio spectrum has been obtained for the protoplanetary nebula candidate HD 179821=IRAS 19114+0002 using the Academy of Sciences Astrophysical Observatory 6-m telescope and CCD detector. The spectroscopic indicators provide the atmospheric parameters T_eff=6800K and logg=1.3 (cgs), approximately equal to those for normal F5 supergiants. A standard local thermodynamic equilibrium (LTE) analysis by the model atmospheres method using these parameters shows that most of the iron-peak elements are at most only slightly deficient ([X]~=-0.10 dex) relative to the normal red giant epsilonVir, however, Sc and Ti are overabundant (~0.5 dex). The alpha-process elements are solar or slightly deficient, except Na, which is overabundant. Carbon and elements heavier than Ni are enhanced by +0.7 dex on average compared with the standard star. The heliocentric radial velocity is found to be +88.4 km s^-1. The detached circumstellar shell, its radial velocity, and the likely overabundance of carbon and s-process elements suggest that HD 179821 is probably an evolved low-mass star in the evolutionary stage between the asymptotic giant branch (AGB) and planetary nebulae (PNe).
Klochkova Valentina G.
Panchuk Vladimir E.
Spelmanis Raivis
Zacs Laimons
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