ATOMIUM: The astounding complexity of the near circumstellar environment of the M-type AGB star R Hydrae

Homan, W.; Pimpanuwat, Bannawit; Herpin, Fabrice; Danilovich, T.; McDonald, Iain; Wallström, Sofia; Richards, A. M. S.; Baudry, A.; Sahai, Raghvendra; Millar, T. J.; Koter, A. de; Gottlieb, C. A.; Kervella, P.; Montargès, M.; Sande, M. Van de; Decin, L.; Zijlstra, A. A.; Etoka, S.; Jeste, Manali; Müller, H. S. P.; Maes, Silke; Malfait, Jolien; Menten, K. M.; Plane, J. M. C.; Lee, Kelvin; Waters, Rens; Wong, K. T.; Lagadec, E.; Gobrecht, David; Yates, J.; Price, Daniel J.; Cannon, Emily; Bolte, John; Ceuster, Frederik De; Nuth, J. A.; Sindel, Jan Philip; Kee, Dylan; Gray, M. D.; Mellah, I. El

doi:10.1051/0004-6361/202140512

Cited by 13 publications

(20 citation statements)

References 69 publications

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“…We took the calibrated data for all ALMA configurations combined, excluding channels with line emission, and fit a uniform disc (UD) to the visibilities (as in [65]). This gave a diameter of 16.7 mas, containing 8.0 mJy.…”

Section: Agb Angular Diametermentioning

confidence: 99%

Chemical tracers of a highly eccentric binary orbit

Danilovich

Malfait

Sande

et al. 2023

Preprint

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Binary interactions have been proposed to explain a variety of circumstellar structures seen around evolved stars, including asymptotic giant branch (AGB) stars and planetary nebulae. Studies resolving the circumstellar envelopes of AGB stars have revealed spirals, discs and bipolar outflows, with shaping attributed to interactions with a companion. For the first time, we have used a combined chemical and dynamical analysis to reveal a highly eccentric and long-period orbit for W~Aquilae, a binary system containing an AGB star and a main sequence companion. Our results are based on anisotropic SiN emission, the first detections of NS and SiC towards an S-type star, and density structures observed in the CO emission. These features are all interpreted as having formed during periastron interactions. Our new method can yield stringent constraints on the orbital parameters of long-period binaries containing AGB stars, and establishes a template for future studies.

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Section: Agb Angular Diametermentioning

confidence: 99%

Chemical tracers of a highly eccentric binary orbit

Danilovich

Malfait

Sande

et al. 2023

Preprint

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“…At a projected distance of 100 au from the centre of the star, the SiO/CO ratio is over two orders of magnitude smaller in Mira A than in R Dor and EP Aqr. The SiO emission of the CSEs of other low mass-loss-rate oxygenrich AGB stars, such as W Hya (Takigawa et al 2017;Hoai et al 2021), RS Cnc (Winters et al 2021), R Leo (Fonfría et al 2019a,b), R Hya (Homan et al 2021) has also been observed at ALMA; in general, the SiO emission, while being significantly more compact than the CO emission, extends beyond 150 au, providing additional evidence for the specificity of Mira Ceti.…”

Section: Confinement At Short Distances Of the Sio Emissions Outside ...mentioning

confidence: 99%

Mira Ceti, atypical archetype

Nhung,

Hoai,

Tuan-Anh

et al. 2021

Preprint

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With the aim of unravelling the complexity of the morpho-kinematics of the circumstellar envelope (CSE) of Mira Ceti, we review, extend and possibly revisit ALMA millimetre observations of the emission of the SiO(5-4) and CO(3-2) molecular lines, including a new analysis of the optically thin 13 CO(3-2) emission. In agreement with observations at shorter wavelengths, we give evidence for confinement of a dense gas volume within ∼50 au from the star and for a broad SiO line-width within ∼15 au. We show that the mass loss rate is episodic and takes the form of clumps having a very low SiO/CO abundance ratio. We evaluate the current mass loss rate as (8±4)×10 −8 M ⊙ yr −1 , much smaller than usually assumed. 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 results from dust grains outgassing SiO molecules, in support of an earlier interpretation in terms of 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: lower mass AGB stars, with a mass loss rate at the level of a few 10 −7 M ⊙ yr −1 and preferably no companion are better suited for developing models of the very complex gas-dust chemistry at stake in the CSE of oxygen-rich AGB stars.

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“…The shaping mechanism(s) of the wind of AGB and post-AGB stars still represent(s) a missing piece in our understanding of their mass loss, and ultimately the formation of the structures seen in planetary nebulae (Decin et al 2020). By combining spatially resolved observations of the circumstellar environment through several molecular transitions, constraints are placed on the masses of the new companions for both π 1 Gru (≲ 1.1 M ⊙ ; Homan et al 2020) and R Hya (≳ 0.65 M ⊙ ; Homan et al 2021). For the S-type star W Aql, observations of halide molecules show that its AlF abundance exceeds the solar fluorine abundance, confirming that fluorine synthesized in situ is already brought to the surface of the AGB star and expelled in its circumstellar environment (Danilovich et al 2021).…”

Section: Introductionmentioning

confidence: 99%

The VLT/SPHERE view of the ATOMIUM cool evolved star sample

Montargès

Cannon

Koter

et al. 2023

A&A

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Context. Low-and intermediate-mass asymptotic giant stars and massive red supergiant stars are important contributors to the chemical enrichment of the Universe. They are among the most efficient dust factories of the Galaxy, harboring chemically rich circumstellar environments. Yet, the processes that lead to dust formation or the large-scale shaping of the mass loss still escape attempts at modeling. Aims. Through the Atomium project, we aim to present a consistent view of a sample of 17 nearby cool evolved stars. Our goals are to unveil the dust-nucleation sites and morphologies of the circumstellar envelope of such stars and to probe ambient environments with various conditions. This will further enhance our understanding of the roles of stellar convection and pulsations, and that of companions in shaping the dusty circumstellar medium.Methods. Here we present and analyze VLT/SPHERE-ZIMPOL polarimetric maps obtained in the visible (645 − 820 nm) of 14 out of the 17 Atomium sources. They were obtained contemporaneously with the ALMA high spatial resolution data. To help interpret the polarized signal, we produced synthetic maps of light scattering by dust, through 3D radiative transfer simulations with the RADMC3D code.Results. The degree of linear polarization (DoLP) observed by ZIMPOL spreads across several optical filters. We infer that it primarily probes dust located just outside of the point spread function of the central source, and in or near the plane of the sky. The polarized signal is mainly produced by structures with a total optical depth close to unity in the line of sight, and it represents only a fraction of the total circumstellar dust. The maximum DoLP ranges from 0.03-0.38 depending on the source, fractions that can be reproduced by our 3D pilot models for grains composed of olivine, melilite, corundum, enstatite, or forsterite. The spatial structure of the DoLP shows a diverse set of shapes, including clumps, arcs, and full envelopes. Only for three sources do we note a correlation between the ALMA CO = 0, J = 2 − 1 and SiO = 0, J = 5 − 4 lines, which trace the gas density, and the DoLP, which traces the dust. Conclusions. The clumpiness of the DoLP and the lack of a consistent correlation between the gas and the dust location show that, in the inner environment, dust formation occurs at very specific sites. This has potential consequences for the derived mass-loss rates and dust-to-gas ratio in the inner region of the circumstellar environment. Except for π 1 Gru and perhaps GY Aql, we do not detect interactions between the circumstellar wind and the hypothesized companions that shape the wind at larger scales. This suggests that the orbits of any other companions are tilted out of the plane of the sky.

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ATOMIUM: The astounding complexity of the near circumstellar environment of the M-type AGB star R Hydrae

Cited by 13 publications

References 69 publications

Chemical tracers of a highly eccentric binary orbit

Chemical tracers of a highly eccentric binary orbit

Mira Ceti, atypical archetype

The VLT/SPHERE view of the ATOMIUM cool evolved star sample

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