Modelling the atmosphere of the carbon-rich Mira RU Vir

Abstract

Context. We study the atmosphere of the carbon-rich Mira RU Vir using the mid-infrared high spatial resolution interferometric observations from VLTI/MIDI. Aims. The aim of this work is to analyse the atmosphere of the carbon-rich Mira RU Vir, with state of the art models, in this way deepening the knowledge of the dynamic processes at work in carbon-rich Miras. Methods. We compare spectro-photometric and interferometric measurements of this carbon-rich Mira AGB star, with the predictions of different kinds of modelling approaches (hydrostatic model atmospheres plus MOD-More Of Dusty, self-consistent dynamic model atmospheres). A geometric model fitting tool is used for a first interpretation of the interferometric data. Results. The results show that a joint use of different kind of observations (photometry, spectroscopy, interferometry) is essential to shed light on the structure of the atmosphere of a carbon-rich Mira. The dynamic model atmospheres fit well the ISO spectrum in the wavelength range λ = [2.9, 25.0] μm. Nevertheless, a discrepancy is noticeable both in the SED (visible), and in the visibilities (shape and level). A possible explanation are intra-/inter-cycle variations in the dynamic model atmospheres as well as in the observations. The presence of a companion star and/or a disk or a decrease of mass loss within the last few hundred years cannot be excluded but are considered unlikely.

15 pages. Accepted in A&A

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• Atmospheres and wind properties of non-spherical AGB stars
• GHRS Observations of Cool, Low-Gravity Stars. VI Mass-Loss Rates and Wind Parameters for M Giants
• The curious case of II Lup: a complex morphology revealed with SAM/NACO and ALMA
• VLTI-GRAVITY measurements of cool evolved stars: I. Variable photosphere and extended atmosphere of the Mira star R Peg
• Constraining stellar parameters and atmospheric dynamics of the carbon AGB star V Oph
• The K-band highest-resolution images of the Mira star R Car with GRAVITY-VLTI
• Bolometric Flux Estimation for Cool Evolved Stars