The wind of the M-type AGB star RT Virginis probed by VLTI/MIDI
arXiv:1301.5872 · doi:10.1051/0004-6361/201220524
Abstract
We study the circumstellar environment of the M-type AGB star RT Vir using mid-infrared high spatial resolution observations from the ESO-VLTI focal instrument MIDI. The aim of this study is to provide observational constraints on theoretical prediction that the winds of M-type AGB objects can be driven by photon scattering on iron-free silicate grains located in the close environment (about 2 to 3 stellar radii) of the star. We interpreted spectro-interferometric data, first using wavelength-dependent geometric models. We then used a self-consistent dynamic model atmosphere containing a time-dependent description of grain growth for pure forsterite dust particles to reproduce the photometric, spectrometric, and interferometric measurements of RT Vir. Since the hydrodynamic computation needs stellar parameters as input, a considerable effort was first made to determine these parameters. MIDI differential phases reveal the presence of an asymmetry in the stellar vicinity. Results from the geometrical modeling give us clues to the presence of aluminum and silicate dust in the close circumstellar environment (< ~5 stellar radii). Comparison between spectro-interferometric data and a self-consistent dust-driven wind model reveals that silicate dust has to be present in the region between 2 to 3 stellar radii to reproduce the 59 and 63 m baseline visibility measurements around 9.8 micron. This gives additional observational evidence in favor of winds driven by photon scattering on iron-free silicate grains located in the close vicinity of an M-type star. However, other sources of opacity are clearly missing to reproduce the 10-13 micron visibility measurements for all baselines. This study is a first attempt to understand the wind mechanism of M-type AGB stars by comparing photometric, spectrometric, and interferometric measurements with state-of-the-art, self-consistent dust-driven wind models. The agreement of the dynamic model atmosphere with interferometric measurements in the 8-10 micron spectral region gives additional observational evidence that the winds of M-type stars can be driven by photon scattering on iron-free silicate grains. Finally, a larger statistical study and progress in advanced self-consistent 3D modeling are still required to solve the remaining problems.
arXiv commentAstronomy and Astrophysics (2013)
References in corpus (30)
- A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
- AGB Variables and the Mira Period-Luminosity Relation
- Too little radiation pressure on dust in the winds of oxygen-rich AGB stars
- A close halo of large transparent grains around extreme red giant stars
- Synthetic photometry for carbon rich giants, I. Hydrostatic dust-free models
- Mass loss rates of a sample of irregular and semiregular M-type AGB-variables
- `Thermal' SiO radio line emission towards M-type AGB stars: a probe of circumstellar dust formation and dynamics
- On the reliability of mass-loss-rate estimates for AGB stars
- High-resolution imaging of dust shells using Keck aperture masking and the IOTA Interferometer
- Radiative hydrodynamics simulations of red supergiant stars. III. Spectro-photocentric variability, photometric variability, and consequences on Gaia measurements
- Classification of 2.4-45.2 Micron Spectra from the ISO Short Wavelength Spectrometer
- Line formation in AGB atmospheres including velocity effects. Molecular line profile variations of long period variables
- The Mira variable S Ori: Relationships between the photosphere, molecular layer, dust shell, and SiO maser shell at 4 epochs
- Near-infrared absorption properties of oxygen-rich stardust analogues: The influence of coloring metal ions
- Exploring wind-driving dust species in cool luminous giants I. Basic criteria and dynamical models of M-type AGB stars
- Evolved star water maser cloud size determined by star size
- Warm water vapor envelope in Mira variables and its effects on the apparent size from the near-infrared to the mid-infrared
- Synthetic photometry for carbon-rich giants II. The effects of pulsation and circumstellar dust
- Atmospheric dynamics in carbon-rich Miras. II. Models meet observations
- Dust and molecular shells in asymptotic giant branch stars - Mid-infrared interferometric observations of R Aql, R Aqr, R Hya, W Hya and V Hya
- Observational evidence for the shrinking of bright maser spots
- Observing and modeling the dynamic atmosphere of the low mass-loss C-star R Sculptoris at high angular resolution
- Three-component modeling of C-rich AGB star winds. II. The effects of drift in long-period variables
- The 3-D kinematics of water masers around the semiregular variable RT Virginis
- Asymmetric silicate dust distribution toward the silicate carbon star BM Gem
- Three-component modeling of C-rich AGB star winds III. Micro-physics of drift-dependent dust formation
- Detection of an asymmetry in the envelope of the carbon Mira R Fornacis using VLTI/MIDI
- The geometry of the close environment of SV Psc as probed by VLTI/MIDI
- Angular diameter estimation of interferometric calibrators - Example of lambda Gruis, calibrator for VLTI-AMBER
- Geometrical model fitting for interferometric data: GEM-FIND
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- Dust formation in the oxygen-rich AGB star IK Tau
- Dynamic atmospheres and winds of cool luminous giants, I. AlO and silicate dust in the close vicinity of M-type AGB stars
- Tracing the phase transition of Al-bearing species from molecules to dust in AGB winds. Constraining the presence of gas-phase (Al2O3)n clusters
- New insights into the dust formation of oxygen-rich AGB stars
- Clumpy dust clouds and extended atmosphere of the AGB star W Hya revealed with VLT/SPHERE-ZIMPOL and VLTI/AMBER
- The evolution of DARWIN: current status of wind models for AGB stars
- An extensive grid of DARWIN models for M-type AGB stars I. Mass-loss rates and other properties of dust-driven winds
- Exploring the origin of clumpy dust clouds around cool giants. A global 3D RHD model of a dust-forming M-type AGB star
- Exploring wind-driving dust species in cool luminous giants II. Constraints from photometry of M-type AGB stars
- Dust-driven winds of AGB stars: The critical interplay of atmospheric shocks and luminosity variations
- The VLTI/MIDI view on the inner mass loss of evolved stars from the Herschel MESS sample
- Dynamic atmospheres and winds of cool luminous giants, II. Gradual Fe enrichment of wind-driving silicate grains
- Exploring the innermost dust formation region of the oxygen-rich AGB star IK~Tau with VLT/SPHERE-ZIMPOL and VLTI/AMBER
- Modelling the atmosphere of the carbon-rich Mira RU Vir
- Modelling polarized light from dust shells surrounding asymptotic giant branch stars
- Tomography of silicate dust around M-type AGB stars I. Diagnostics based on dynamical models
- ALMA monitoring of mm line variation in IRC+10216: I. Overview of millimeter variability
- Eppur si eclissa: Eccentric low-mass companions and time-in-dust selection explain long secondary periods
- Spatially resolving the atmosphere of the non-Mira-type AGB star SW Vir in near-infrared molecular and atomic lines with VLTI/AMBER
- H2O Maser Emission in Circumstellar Envelopes around AGB Stars: Physical Conditions in Gas-Dust Clouds
- From the atmosphere to the circumstellar environment in cool evolved stars