Insights into the planetary dynamics of HD 206893 with ALMA. Issue 1 (31st August 2020)

• Record Type: Journal Article
• Authors: Marino, S; Zurlo, A; Faramaz, V; Milli, J; Henning, Th; Kennedy, G M; Matrà, L; Pérez, S; Delorme, P; Cieza, L A; Hughes, A M
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 498:Issue 1(2020)
• Page Start: 1319
• Page End: 1334
• Publication Date: 2020-08-31
• Subjects: methods: numerical -- techniques: interferometric -- planets and satellites: dynamical evolution and stability -- circumstellar matter -- stars: individual: HD 206893 -- submillimetre: planetary systems; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa2386
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Radial substructure in the form of rings and gaps has been shown to be ubiquitous among protoplanetary discs. This could be the case in exo-Kuiper belts as well, and evidence for this is emerging. In this paper, we present ALMA observations of the debris/planetesimal disc surrounding HD 206893, a system that also hosts two massive companions at 2 and 11 au. Our observations reveal a disc extending from 30 to 180 au, split by a 27 au wide gap centred at 74 au, and no dust surrounding the reddened brown dwarf (BD) at 11 au. The gap width suggests the presence of a 0.9 M Jup planet at 74 au, which would be the third companion in this system. Using previous astrometry of the BD, combined with our derived disc orientation as a prior, we were able to better constrain its orbit finding it is likely eccentric ($0.14^{+0.05}_{-0.04}$ ). For the innermost companion, we used radial velocity, proper motion anomaly, and stability considerations to show its mass and semimajor axis are likely in the ranges 4–100 M Jup and 1.4–4.5 au. These three companions will interact on secular time-scales and perturb the orbits of planetesimals, stirring the disc and potentially truncating it to its current extent via secular resonances. Finally, the presence of a gap in this system adds to the growing evidence that gaps could be common in wide exo-Kuiper belts. Out of six wide debris discs observed with ALMA with enough resolution, four to five show radial substructure in the form of gaps.