Large-scale environments of binary AGB stars probed by Herschel - I. Morphology statistics and case studies of R Aquarii and W Aquilae

Abstract

The Mass loss of Evolved StarS (MESS) sample offers a selection of 78 Asymptotic Giant Branch (AGB) stars and Red Supergiants (RSGs) observed with the PACS photometer on-board Herschel at 70 and 160 μm. For most of these objects, the dusty AGB wind differs from spherical symmetry and the wind shape can be subdivided into four classes. In the present paper we concentrate on the influence of a companion on the morphology of the stellar wind. Literature was searched to find binaries in the MESS sample and these are subsequently linked to their wind-morphology class to assert that the binaries are not distributed equally among the classes. In the second part of the paper we concentrate on the circumstellar environment of the two prominent objects R Aqr and W Aql. Each shows a characteristic signature of a companion interaction with the stellar wind. For the symbiotic star R Aqr, PACS revealed two perfectly opposing arms which in part reflect the previously observed ring-shaped nebula in the optical. However, from the far-IR there is evidence that the emitting region is elliptical rather than circular. The outline of the wind of W Aql seems to follow a large Archimedean spiral formed by the orbit of the companion but also shows strong indications of an interaction with the interstellar medium. The nature of the companion of W Aql was investigated and the magnitude of the orbital period supports the size of the spiral outline.

14 pages, 9 figures, 5 tables

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Cited by in corpus (16)

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• The circumstellar envelope around the S-type AGB star W Aql Effects of an eccentric binary orbit
• Rings and arcs around evolved stars. II. The Carbon Star AFGL 3068 and the Planetary Nebulae NGC 6543, NGC 7009 and NGC 7027
• The VLT/SPHERE view of the ATOMIUM cool evolved star sample. I. Overview: Sample characterization through polarization analysis
• Surprising detection of an equatorial dust lane on the AGB star IRC+10216
• Eyes in the sky: Interactions between AGB winds and the interstellar magnetic field
• Large-scale environments of binary AGB stars probed by Herschel. II: Two companions interacting with the wind of pi1 Gruis
• Chemical tracers of a highly eccentric AGB-main sequence star binary
• Classifying the secondary component of the binary star W Aquilae
• An XMM-Newton EPIC X-ray view of the Symbiotic Star R~Aquarii
• A large bubble around the AGB star R Dor detected in the UV
• SOFIA/FORCAST Monitoring of the Dust Emission from R Aqr: Start of the Eclipse
• Extended view on the dust shells around two carbon stars