ATOMIUM: The astounding complexity of the near circumstellar environment of the M-type AGB star R Hydrae. I. Morpho-kinematical interpretation of CO and SiO emission - Archive ouverte HAL Access content directly
Journal Articles Astronomy and Astrophysics - A&A Year : 2021

## ATOMIUM: The astounding complexity of the near circumstellar environment of the M-type AGB star R Hydrae. I. Morpho-kinematical interpretation of CO and SiO emission

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Ward Homan
• Function : Author
Bannawit Pimpanuwat
• Function : Author
Fabrice Herpin
• Function : Author
Taissa Danilovich
• Function : Author
Iain Mcdonald
• Function : Author
Sofia H. J. Wallström
• Function : Author
Anita M. S. Richards
• Function : Author
Alain Baudry
• Function : Author
Raghvendra Sahai
• Function : Author
Tom J. Millar
• Function : Author
Alex de Koter
• Function : Author
C. A. Gottlieb
• Function : Author
Pierre Kervella
Marie van de Sande
• Function : Author
Leen Decin
• Function : Author
Albert Zijlstra
• Function : Author
Sandra Etoka
• Function : Author
Manali Jeste
• Function : Author
Holger S. P. Müller
• Function : Author
Silke Maes
• Function : Author
Jolien Malfait
• Function : Author
Karl Menten
John Plane
Kelvin Lee
• Function : Author
Rens Waters
• Function : Author
Ka Tat Wong
• Function : Author
• Function : Author
David Gobrecht
• Function : Author
Jeremy Yates
• Function : Author
Daniel Price
Emily Cannon
• Function : Author
Jan Bolte
• Function : Author
Frederik de Ceuster
• Function : Author
Joe Nuth
• Function : Author
Jan Philip Sindel
• Function : Author
Dylan Kee
• Function : Author
Malcolm D. Gray
• Function : Author

#### Abstract

Evolved low- to intermediate-mass stars are known to shed their gaseous envelope into a large, dusty, molecule-rich circumstellar nebula which typically develops a high degree of structural complexity. Most of the large-scale, spatially correlated structures in the nebula are thought to originate from the interaction of the stellar wind with a companion. As part of the ATOMIUM large programme, we observed the M-type asymptotic giant branch (AGB) star R Hydrae with the Atacama Large Millimeter/submillimeter Array. The morphology of the inner wind of R Hya, which has a known companion at ∼3500 au, was determined from maps of CO and SiO obtained at high angular resolution. A map of the CO emission reveals a multi-layered structure consisting of a large elliptical feature at an angular scale of ∼10″ that is oriented along the north-south axis. The wind morphology within the elliptical feature is dominated by two hollow bubbles. The bubbles are on opposite sides of the AGB star and lie along an axis with a position angle of ∼115°. Both bubbles are offset from the central star, and their appearance in the SiO channel maps indicates that they might be shock waves travelling through the AGB wind. An estimate of the dynamical age of the bubbles yields an age of the order of 100 yr, which is in agreement with the previously proposed elapsed time since the star last underwent a thermal pulse. When the CO and SiO emission is examined on subarcsecond angular scales, there is evidence for an inclined, differentially rotating equatorial density enhancement, strongly suggesting the presence of a second nearby companion. The position angle of the major axis of this disc is ∼70° in the plane of the sky. We tentatively estimate that a lower limit on the mass of the nearby companion is ∼0.65 M on the basis of the highest measured speeds in the disc and the location of its inner rim at ∼6 au from the AGB star.

### Dates and versions

insu-03678883 , version 1 (25-05-2022)

### Identifiers

• HAL Id : insu-03678883 , version 1
• ARXIV :
• BIBCODE :
• DOI :

### Cite

Ward Homan, Bannawit Pimpanuwat, Fabrice Herpin, Taissa Danilovich, Iain Mcdonald, et al.. ATOMIUM: The astounding complexity of the near circumstellar environment of the M-type AGB star R Hydrae. I. Morpho-kinematical interpretation of CO and SiO emission. Astronomy and Astrophysics - A&A, 2021, 651, ⟨10.1051/0004-6361/202140512⟩. ⟨insu-03678883⟩

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