Universität zu Köln

Rau, G., Hron, J., Paladini, C., Aringer, B., Eriksson, K., Marigo, P., Nowotny, W. and Grellmann, R. (2017). The adventure of carbon stars Observations and modeling of a set of C-rich AGB stars. Astron. Astrophys., 600. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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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 mu m, and the interferometric observations between 8 mu m and 10 mu m. Discrepancies observed at wavelengths shorter than 1 mu m in the SED, and longer than 10 mu m 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. M. Our findings agree well with literature values within the uncertainties. TRoss, and LRoss are also in good agreement with the temperature derived from the angular diameter T(theta((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, theta(Ross) and theta((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.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Rau, G. UNSPECIFIED UNSPECIFIED UNSPECIFIED Hron, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Paladini, C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Aringer, B. UNSPECIFIED UNSPECIFIED UNSPECIFIED Eriksson, K. UNSPECIFIED UNSPECIFIED UNSPECIFIED Marigo, P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Nowotny, W. UNSPECIFIED UNSPECIFIED UNSPECIFIED Grellmann, R. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-234677
DOI:	10.1051/0004-6361/201629337
Journal or Publication Title:	Astron. Astrophys.
Volume:	600
Date:	2017
Publisher:	EDP SCIENCES S A
Place of Publication:	LES ULIS CEDEX A
ISSN:	1432-0746
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language LONG-PERIOD VARIABLES; DRIVEN MASS-LOSS; SYNTHETIC PHOTOMETRY; STELLAR PARAMETERS; DUST FORMATION; OPTICAL-PROPERTIES; ATMOSPHERIC DYNAMICS; LOSS RATES; WINDS; I. Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/23467