Volume 616, August 2018
|Number of page(s)||6|
|Section||Letters to the Editor|
|Published online||14 August 2018|
Letter to the Editor
High-resolution observations of the symbiotic system R Aqr
Direct imaging of the gravitational effects of the secondary on the stellar wind
Observatorio Astronómico Nacional (OAN-IGN), Apartado 112, 28803 Alcalá de Henares, Spain
2 Observatorio Astronómico Nacional (OAN-IGN), C/ Alfonso XII, 3, 28014 Madrid, Spain
3 Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland
4 Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 Saint Martin d’Hères, France
5 Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden
Accepted: 11 July 2018
We have observed the symbiotic stellar system R Aqr, aiming to describe the gravitational interaction between the white dwarf (WD) and the wind from the Mira star, the key phenomenon driving the symbiotic activity and the formation of nebulae in such systems. We present high-resolution ALMA maps of the 12CO and 13CO J = 3−2 lines, the 0.9 mm continuum distribution, and some high-excitation molecular lines in R Aqr. The maps, which have resolutions ranging between 40 mas and less than 20 mas probe the circumstellar regions at suborbital scales as the distance between the stars is ~40 mas. Our observations show the gravitational effects of the secondary on the stellar wind. The AGB star was identified in our maps from the continuum and molecular line data, and we estimated the probable position of the secondary from a new estimation of the orbital parameters. The (preliminary) comparison of our maps with theoretical predictions is surprisingly satisfactory and the main expected gravitational effects are directly mapped for the first time. We find a strong focusing in the equatorial plane of the resulting wind, which shows two plumes in opposite directions that have different velocities and very probably correspond to the expected double spiral due to the interaction. Our continuum maps show the very inner regions of the nascent bipolar jets, at scales of some AU. Continuum maps obtained with the highest resolution show the presence of a clump that very probably corresponds to the emission of the ionized surroundings of the WD and of a bridge of material joining both stars, which is likely material flowing from the AGB primary to the accretion disk around the WD secondary.
Key words: stars: AGB and post-AGB / circumstellar matter / binaries : close / binaries: symbiotic / stars: individual: R Aqr
© ESO 2018
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