High-resolution observations of gas and dust around Mira using ALMA and SPHERE/ZIMPOL

Abstract

The outflows of oxygen-rich asymptotic giant branch (AGB) stars are thought to be driven by radiation pressure by photon scattering on grains with sizes of tenths of microns. The details of the formation of dust in the extended atmospheres of these stars and the mass-loss process is still not well understood. We obtained quasi-simultaneous observations of the AGB star Mira using ALMA and ZIMPOL to probe the distribution of gas and large dust grains, respectively. The polarized light images show dust around Mira~A, the companion (Mira~B) and in a trail that connects the two sources. ALMA reveals that dust around Mira~A is contained in a high-gas-density region with a significant fraction of the polarized light arising from its edge. We constrained the gas density, temperature, and velocity within a few stellar radii from the star by modelling the CO $v=1,J=3-2$ line. We find a mass $(\sim 3.8\pm 1.3)\times 10^{-4}{M}_{\odot }$ to be contained between the stellar millimetre photosphere, $R_{\star }^{338\mathrm{GHz}}$, and $4R_{\star }^{338\mathrm{GHz}}$. Our best-fit models with lower masses also reproduce the ${}^{13}$CO $v=0,J=3-2$ line emission from this region. We find TiO${}_2$ and AlO abundances corresponding to 4.5% and $<0.1$% of the total titanium and aluminium expected for a solar-composition gas. The low abundance of AlO allows for efficient Al depletion into dust already very close to the star, as expected from thermal dust emission observations and theoretical calculations of Mira variables. We constrain the presence of aluminium oxide grains based on the scattered light observations and our gas-phase model. We find that aluminium oxide grains can account for a significant fraction of the total aluminium atoms in this region only if the grains have sizes $\lesssim 0.02\mu$m. This is an order of magnitude smaller than the maximum sizes predicted by dust-formation and wind-driving models.

arXiv comment16 pages, 10 figures

References in corpus (37)

• The chemical composition of the Sun
• Validation of the new Hipparcos reduction
• Radiative transfer in very optically thick circumstellar disks
• Dust formation in the oxygen-rich AGB star IK Tau
• 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
• UVMULTIFIT: A versatile tool for fitting astronomical radio interferometric data
• SPHERE / ZIMPOL high resolution polarimetric imager. I. System overview, PSF parameters, coronagraphy, and polarimetry
• Global 3D radiation-hydrodynamics models of AGB stars. Effects of convection and radial pulsations on atmospheric structures
• Dynamic atmospheres and winds of cool luminous giants, I. Al${}_2$O${}_3$ and silicate dust in the close vicinity of M-type AGB stars
• Study of the inner dust envelope and stellar photosphere of the AGB star R Doradus using SPHERE/ZIMPOL
• Tracing the phase transition of Al-bearing species from molecules to dust in AGB winds. Constraining the presence of gas-phase (Al2O3)n clusters
• X-ray Outburst in Mira A
• The close circumstellar environment of Betelgeuse - V. Rotation velocity and molecular envelope properties from ALMA
• Dynamical Opacity-Sampling Models of Mira Variables. II: Time-Dependent Atmospheric Structure and Observable Properties of 4 M-Type Model Series
• Exploring wind-driving dust species in cool luminous giants I. Basic criteria and dynamical models of M-type AGB stars
• New insights into the dust formation of oxygen-rich AGB stars
• The wonderful complexity of the Mira AB system
• Clumpy dust clouds and extended atmosphere of the AGB star W Hya revealed with VLT/SPHERE-ZIMPOL and VLTI/AMBER
• An observational study of dust nucleation in Mira ($o$ Ceti): I. Variable features of AlO and other Al-bearing species
• Carbon and oxygen isotopic ratios for nearby miras
• Resolving the extended atmosphere and the inner wind of Mira ($o$ Ceti) with long ALMA baselines
• Clumpy dust clouds and extended atmosphere of the AGB star W Hya revealed with VLT/SPHERE-ZIMPOL and VLTI/AMBER II. Time variations between pre-maximum and minimum light
• SPHERE / ZIMPOL observations of the symbiotic system R Aqr. I. Imaging of the stellar binary and the innermost jet clouds
• The Keck Aperture Masking Experiment: spectro-interferometry of 3 Mira Variables from 1.1 to 3.8 microns
• Born Again Protoplanetary Disk Around Mira B
• Magnetically aligned dust and SiO maser polarization in the envelope of the red supergiant VY CMa
• 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
• The shock-heated atmosphere of an asymptotic giant branch star resolved by ALMA
• An observational study of dust nucleation in Mira ($o$ Ceti): II. Titanium oxides are negligible for nucleation at high temperatures
• Silicate condensation in Mira variables
• ALMA observations of the vibrationally-excited rotational CO transition $v=1,J=3-2$ towards five AGB stars
• Dusty wind of W Hya. Multi-wavelength modelling of the present-day and recent mass-loss
• Accurate laboratory rest frequencies of vibrationally excited CO up to $varv=3$ and up to 2 THz
• Comparison of dynamical model atmospheres of Mira variables with mid-infrared interferometric and spectroscopic observations
• Modelling polarized light from dust shells surrounding asymptotic giant branch stars
• Optical properties of amorphous alumina dust in the envelopes around O-rich AGB stars

Cited by in corpus (26)

• Chemical equilibrium in AGB atmospheres: Successes, failures, and prospects for small molecules, clusters, and condensates
• Exploring the origin of clumpy dust clouds around cool giants. A global 3D RHD model of a dust-forming M-type AGB star
• Resolving the extended stellar atmospheres of Asymptotic Giant Branch stars at (sub-)millimetre wavelengths
• ATOMIUM: ALMA tracing the origins of molecules in dust forming oxygen rich M-type stars: Motivation, sample, calibration, and initial results
• Developing a self-consistent AGB wind model: II. Non-classical, non-equilibrium polymer nucleation in a chemical mixture
• Inner dusty envelope of the AGB stars W~Hydrae, SW\,Virginis, and R~Crateris using SPHERE/ZIMPOL
• Exploring the innermost dust formation region of the oxygen-rich AGB star IK~Tau with VLT/SPHERE-ZIMPOL and VLTI/AMBER
• Rotational spectra of vibrationally excited AlO and TiO in oxygen rich stars
• Atmospheric molecular blobs shape up circumstellar envelopes of AGB stars
• The VLT/SPHERE view of the ATOMIUM cool evolved star sample. I. Overview: Sample characterization through polarization analysis
• Infrared interferometric three-dimensional diagnosis of the atmospheric dynamics of the AGB star R Dor with VLTI/AMBER
• Modeling rotational disruption of grains and microwave emission from spinning dust in AGB envelopes
• Evidence for localized onset of episodic mass loss in Mira
• First detection of AlF line emission towards M-type AGB stars
• The unusual 3D distribution of NaCl around the AGB star IK Tau
• Revealing new features of the millimetre emission of the circumbinary envelope of Mira Ceti
• Mira Ceti, atypical archetype
• Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri
• Maser emission from the CO envelope of the asymptotic giant branch star W Hydrae
• Contemporaneous high-angular-resolution imaging of the AGB star W Hya in vibrationally excited H2O lines and visible polarized light with ALMA and VLT/SPHERE-ZIMPOL
• Evidence for episodic and patchy mass ejection in the circumstellar envelope of AGB star R Leonis
• High-angular-resolution ALMA imaging of the inhomogeneous dynamical atmosphere of the asymptotic giant branch star W Hya
• Effects of Metallicity on Graphite, TiC, and SiC Condensation in Carbon Stars
• Molecules and Chemistry in Red Supergiants
• 3D models of the circumstellar environments of evolved stars: Formation of multiple spiral structures
• Probing sulfur chemistry in oxygen-rich AGB stars with ALMA