Unseen companions of V Hya inferred from periodic ejections. Issue 3 (3rd June 2019)

• Record Type: Journal Article
• Authors: Salas, Jesus M; Naoz, Smadar; Morris, Mark R; Stephan, Alexander P
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 487:Issue 3(2019)
• Page Start: 3029
• Page End: 3036
• Publication Date: 2019-06-03
• Subjects: binaries: general -- stars: evolution -- stars: kinematics and dynamics; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stz1515
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: A recent study using Hubble Space Telescope observations found periodic, high-speed, collimated ejections (or 'bullets') from the star V Hya. The authors of that study proposed a model associating these bullets with the periastron passage of an unseen, substellar companion in an eccentric orbit and with an orbital period of ∼8 yr. Here we propose that V Hya is part of a triple system, with a substellar companion having an orbital period of ∼8 yr, and a tertiary object on a much wider orbit. In this model, the more distant object causes high-eccentricity excitations on the substellar companion's orbit via the Eccentric Kozai–Lidov mechanism. These eccentricities can reach such high values that they lead to Roche-lobe crossing, producing the observed bullet ejections via a strongly enhanced accretion episode. For example, we find that a ballistic bullet ejection mechanism can be produced by a brown-dwarf-mass companion, while magnetically driven outflows are consistent with a Jovian-mass companion. Finally, we suggest that the distant companion may reside at few a hundred astronomical units on an eccentric orbit.