Mira Ceti, atypical archetype

Abstract

With the aim of unraveling the complexity of the morpho-kinematics of the circumstellar envelope (CSE) of Mira Ceti, we review, extend and in some cases revisit ALMA millimeter observations of the emission of the SiO(5-4) and CO(3-2) molecular lines. In addition, we present a detailed analysis of the optically thin ${}^{13}$CO(3-2) emission, which provides several important new results. In agreement with observations at infrared and visible wavelengths, we give evidence for confinement and probably rotation of a dense gas volume within $\sim$50 au from the star and for a large SiO line-width within $\sim$15 au. We show that the mass loss process is episodic and takes the form of clumps having a very low SiO/CO abundance ratio compared with similar oxygen-rich long period variables, probably a result of depletion on dust grains and photo-dissociation. We evaluate the mass loss rate associated with the main clumps and compare it with values obtained from single dish observations. We argue that the SiO emission observed in the south-western quadrant is not related to the mechanism of generation of the nascent wind but to a mass ejection that occurred eleven years before the observations. We remark that Mira Ceti is not a good archetype in terms of its wind: models aiming at describing the very complex gas-dust chemistry in action in the CSE of oxygen-rich AGB stars may find it difficult to account for its peculiar features, small variations in the parameters deciding when and where mass loss can proceed significantly.

21 pages, 17 figures

References in corpus (15)

• SiO line emission from C-type shock waves : interstellar jets and outflows
• Resolving the stellar activity of the Mira AB binary with ALMA
• Too little radiation pressure on dust in the winds of oxygen-rich AGB stars
• The wonderful complexity of the Mira AB system
• Carbon and oxygen isotopic ratios for nearby miras
• A Catalog of GALEX Ultraviolet Emission from Asymptotic Giant Branch Stars
• Resolving the extended stellar atmospheres of Asymptotic Giant Branch stars at (sub-)millimetre wavelengths
• An observational study of dust nucleation in Mira ($o$ Ceti): II. Titanium oxides are negligible for nucleation at high temperatures
• ALMA observations of the vibrationally-excited rotational CO transition $v=1,J=3-2$ towards five AGB stars
• Cometary Astropause of Mira Revealed in the Far-Infrared
• Mira B Rejuvenated
• The morpho-kinematics of the circumstellar envelope around the AGB star EP Aqr
• Observation of narrow polar jets in the nascent wind of oxygen-rich AGB star EP Aqr
• Revealing new features of the millimetre emission of the circumbinary envelope of Mira Ceti
• Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri

Cited by in corpus (4)

• The OGLE Collection of Variable Stars. Nearly 66,000 Mira stars in the Milky Way
• Evidence for episodic and patchy mass ejection in the circumstellar envelope of AGB star R Leonis
• Contributions of rotation, expansion and line broadening to the morpho-kinematics of the inner CSE of oxygen-rich AGB star R Hya
• Millimetre observations of the S-type AGB star $\chi$ Cygni: variability of the emission of the inner envelope