The adventure of carbon stars. Observations and modeling of a set of C-rich AGB stars
- Author(s)
- Gioia Rau, Josef Hron, Claudia Paladini, Bernhard Aringer, Walter Nowotny-Schipper
- Abstract
Context. Modeling stellar atmospheres is a complex and intriguing task in modern astronomy. A systematic comparison of models with multi-technique observations is the only efficient way to constrain the models. Aims. We intend to perform self-consistent modeling of the atmospheres of six carbon-rich AGB stars (R Lep, R Vol, Y Pav, AQ Sgr, U Hya, and X TrA) with the aim of enlarging the knowledge of the dynamic processes occurring in their atmospheres. Methods. We used VLTI/MIDI interferometric observations, in combination with spectro-photometric data, and compared them with self-consistent, dynamic model atmospheres. Results. We found that the models can reproduce spectral energy distribution (SED) data well at wavelengths longer than 1 μm, and the interferometric observations between 8 μm and 10 μm. Discrepancies observed at wavelengths shorter than 1 μm in the SED, and longer than 10 μm in the visibilities, could be due to a combination of data- and model-related effects. The models best fitting the Miras are significantly extended, and have a prominent shell-like structure. On the contrary, the models best fitting the non-Miras are more compact, showing lower average mass loss. The mass loss is of episodic or multi-periodic nature but causes the visual amplitudes to be notably larger than the observed ones. A number of stellar parameters were derived from the model fitting: T
Ross, L
Ross, M, C/O, and. Our findings agree well with literature values within the uncertainties. T
Ross, and L
Ross are also in good agreement with the temperature derived from the angular diameter T(θ
(V-K)) and the bolometric luminosity from the SED fitting L
bol, except for AQ Sgr. The possible reasons are discussed in the text. Finally, θ
Ross and θ
(V-K) agree with one another better for the Miras than for the non-Miras targets, which is probably connected to the episodic nature of the latter models. We also located the stars in the H-R diagram, comparing them with evolutionary tracks. We found that the main derived properties (L, T
eff, C/O ratios and stellar masses) from the model fitting are in good agreement with TP-AGB evolutionary calculations for carbon stars carried out with the COLIBRI code.
- Organisation(s)
- Department of Astrophysics
- External organisation(s)
- Université Libre de Bruxelles, Osservatorio Astronomico
- Journal
- Astronomy & Astrophysics
- Volume
- 600
- No. of pages
- 21
- ISSN
- 0004-6361
- DOI
- https://doi.org/10.1051/0004-6361/201629337
- Publication date
- 04-2017
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 103003 Astronomy, 103004 Astrophysics
- Keywords
- ASJC Scopus subject areas
- Astronomy and Astrophysics, Space and Planetary Science
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/aa1759ea-da2b-4f36-bbab-59f9e2e470ec