Astronomy and Astrophysics – Astronomy
Scientific paper
Apr 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999aj....117.1834r&link_type=abstract
The Astronomical Journal, Volume 117, Issue 4, pp. 1834-1844.
Astronomy and Astrophysics
Astronomy
27
Stars: Abundances, Stars: Evolution, Stars: Individual: Alphanumeric: Iras 19114-0002, Stars: Individual: Henry Draper Number: Hd 179821, Stars: Supergiants
Scientific paper
A detailed chemical composition analysis of the bright post-AGB candidate HD 179821 (IRAS 19114+0002) is presented. The LTE analysis, based on high-resolution (R~50,000) and high-quality (S/N~300) spectra, yields atmospheric parameters T_eff=6750 K, log g=0.5, and xi_t=5.25 km s^-1. The elemental abundance results of HD 179821 are found to be [Fe/H]=-0.1, [C/Fe]=+0.2,[N/Fe]=+1.3, [O/Fe]=+0.2, [alpha-process/Fe]=+0.5, and [s-process/Fe]=+0.4. These values clearly differ from the elemental abundances of Population I F supergiants. The C, N, and O abundances and the total CNO abundance value relative to Fe, [C+N+O/Fe]=+0.5, indicate that the photosphere of HD 179821 is contaminated with both the H- and He-burning products of the AGB phase. The evidence for He burning through the 3alpha process and deep AGB mixing also comes from the observed overabundances of s-process elements. Remarkably, the abundance of the alpha-process element Na is found to be very large, [Na/Fe]=+0.9. The ratio O/C=2.6 indicates that the atmosphere is oxygen rich. The results of this abundance study support the argument that HD 179821 is a proto-planetary nebula, probably with an intermediate-mass progenitor. However, the strength of the O I triplet lines at 7774 Å and the distance derived from the interstellar Na I D1 and D2 components imply that the star is a luminous object (M_bol~-8.9+/-1) and thus a massive supergiant. Thus, while this study contributes important new observational results for this star, an unambiguous determination of its evolutionary status has yet to be achieved.
Hrivnak Bruce J.
Reddy Bacham E.
No associations
LandOfFree
Spectroscopic Study of HD 179821 (IRAS 19114+0002): Proto-Planetary Nebulaor Supergiant? does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Spectroscopic Study of HD 179821 (IRAS 19114+0002): Proto-Planetary Nebulaor Supergiant?, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Spectroscopic Study of HD 179821 (IRAS 19114+0002): Proto-Planetary Nebulaor Supergiant? will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1429511