V892 Tau: A tidally perturbed circumbinary disc in a triple stellar system

TL;DR

This study uses high-resolution ALMA observations and hydrodynamical simulations to analyze the dynamics of a circumbinary disc in the V892 Tau system, revealing a misaligned, eccentric companion influencing disc features and planetary stability.

Contribution

It provides the first detailed modeling of V892 Tau as a triple system with a misaligned, eccentric companion affecting disc morphology and stability.

Findings

Disc shows non-Keplerian features like spiral arms.

Eccentricity of 0.5 for the companion reproduces disc extent.

Misaligned orbit causes disc oscillation and precession.

Abstract

V892 Tau is a young binary star surrounded by a circumbinary disc which show hints of interaction with the low-mass nearby star V892 Tau NE. The goal of this paper is to constrain the orbit of V892 Tau NE and to determine the resulting circumbinary disc dynamics. We present new ALMA observations of the V892 Tau circumbinary disc at a twice higher angular and spectral resolution. We model the data with V892 Tau as a triple system and perform a grid of hydrodynamical simulations testing several orbits of the companion. The simulation outputs are then post-processed to build synthetic maps that we compare to the observations. The 12CO emission of the disc shows clear non-Keplerian features such as spiral arms. When comparing the data with our synthetic observations, we interpret these features as ongoing interactions with the companion. Our simulations indicate that an eccentricity of 0.5 of the companion is needed to reproduce the observed disc extent and that a mutual inclination of approximately 60{\deg} with the inner binary reproduces the measured disc tilt. In order to explain most of the features of the circumbinary disc, we propose that V892 Tau NE follows a misaligned eccentric orbit, with an eccentricity between 0.2 and 0.5 and a mutual inclination between 30{\deg} and 60{\deg}. Such a misaligned companion suggests the disc is oscillating and precessing with time, stabilising in an intermediate plane with a non-zero mutual inclination with the inner binary. Given that orbital configuration, we show that the stability of future planets is compromised in the second half of the disc once the gas has dissipated.