# Unseen companions of V Hya inferred from periodic ejections

## TL;DR

This paper proposes a triple system model for V Hya, where a distant companion influences a closer substellar object to produce periodic high-speed ejections, explaining observed phenomena.

## Contribution

It introduces a triple system model involving the Eccentric Kozai-Lidov mechanism to explain periodic ejections from V Hya, a novel approach compared to previous binary models.

## Key findings

- A triple system can produce high-eccentricity orbits leading to ejections.
- Ballistic ejections are consistent with brown-dwarf companions.
- Magnetic outflows fit Jovian-mass companions.

## 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 $\sim8$ yrs. Here we propose that V Hya is part of a triple system, with a substellar companion having an orbital period of $\sim8$ yrs, 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 AU on an eccentric orbit.