Interferometric observations of SiO thermal emission in the inner wind of M-type AGB stars IK Tauri and IRC+10011

Abstract

Context. AGB stars go through a process of strong mass-loss that involves pulsations of the atmosphere, which extends to a region where the conditions are adequate for dust grains to form. Radiation pressure acts on these grains which, coupled to the gas, drive a massive outflow. The details of this process are not clear, including which molecules are involved in the condensation of dust grains. Aims. To study the role of the SiO molecule in the process of dust formation and mass-loss in M-type AGB stars. Methods. Using the IRAM NOEMA interferometer we observed the ${}^{28}$SiO and ${}^{29}$SiO $J=3-2$, $v=0$ emission from the inner circumstellar envelope of the evolved stars IK Tau and IRC+10011. We computed azimuthally averaged emission profiles to compare the observations to models using a molecular excitation and ray-tracing code for SiO thermal emission. Results. We observed circular symmetry in the emission distribution. We also found that the source diameter varies only marginally with radial velocity, which is not the expected behavior for envelopes expanding at an almost constant velocity. The adopted density, velocity, and abundance laws, together with the mass-loss rate, which best fit the observations, give us information on the chemical behavior of the SiO molecule and its role in the dust formation process. Conclusions. The results indicate that there is a strong coupling between the depletion of gas phase SiO and gas acceleration in the inner envelope. This could be explained by the condensation of SiO into dust grains.

References in corpus (16)

• Gaia Data Release 2. Summary of the contents and survey properties
• An atomic and molecular database for analysis of submillimetre line observations
• Dust formation in the oxygen-rich AGB star IK Tau
• `Thermal' SiO radio line emission towards M-type AGB stars: a probe of circumstellar dust formation and dynamics
• Coordinated Analyses of Presolar Grains in the Allan Hills 77307 and Queen Elizabeth Range 99177 Meteorites
• The millimeter IRAM-30m line survey toward IK Tau
• New insights into the dust formation of oxygen-rich AGB stars
• ALMA spectral line and imaging survey of a low and a high mass-loss rate AGB star between 335 and 362 GHz
• The dust disk and companion of the nearby AGB star L2 Puppis - SPHERE/ZIMPOL polarimetric imaging at visible wavelengths
• Probing the inner wind of AGB stars: Interferometric observations of SiO millimetre line emission from the oxygen-rich stars R Dor and L2 Pup
• The distribution of SiO in the circumstellar envelope around IRC+10216
• 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
• Bipolar outflow on the Asymptotic Giant Branch - the case of IRC+10011
• ALMA detection of a tentative nearly edge-on rotating disk around the nearby AGB star R~Doradus
• Silicate condensation in Mira variables
• Uniform Silicon Isotope Ratios Across the Milky Way Galaxy

Cited by in corpus (5)

• (Sub)stellar companions shape the winds of evolved stars
• Dust-gas chemistry in AGB outflows: Chemical modelling of dust-gas chemistry within AGB outflows I. Effect on the gas-phase chemistry
• Chemical modelling of dust-gas chemistry within AGB outflows -- II. Effect of the dust-grain size distribution
• Chemistry of nebulae around binary post-AGB stars: A molecular survey of mm-wave lines
• Multi-line study of the radial extent of SiO, CS, and SiS in AGB envelopes