94 Ceti: a triple star with a planet and dust disc

TL;DR

This study models the dust emission and orbital dynamics of the triple star system 94 Ceti, revealing a stable circumbinary debris disc and potential additional circumtertiary ring, providing insights into its planetary system configuration.

Contribution

It offers the first detailed modeling of dust emission and orbital dynamics for 94 Ceti, identifying a stable circumbinary debris disc and possible tertiary ring.

Findings

Debris disc around 94 Ceti is limited to radii smaller than 40 AU.

The dust-to-star luminosity ratio is approximately 4.6×10^-6.

System is dynamically stable with a tentative circumtertiary ring.

Abstract

94 Ceti is a triple star system with a circumprimary gas giant planet and far-infrared excess. Such excesses around main sequence stars are likely due to debris discs, and are considered as signposts of planetary systems and, therefore, provide important insights into the configuration and evolution of the planetary system. Consequently, in order to learn more about the 94 Ceti system, we aim to precisely model the dust emission to fit its observed SED and to simulate its orbital dynamics. We interpret our APEX bolometric observations and complement them with archived Spitzer and Herschel bolometric data to explore the stellar excess and to map out background sources in the fields. Dynamical simulations and 3D radiative transfer calculations were used to constrain the debris disc configurations and model the dust emission. The best fit dust disc model for 94 Ceti implies a circumbinary disc around the secondary pair, limited by dynamics to radii smaller than 40 AU and with a grain size power-law distribution of ~a^-3.5. This model exhibits a dust-to-star luminosity ratio of 4.6+-0.4*10^-6. The system is dynamically stable and N-body symplectic simulations results are consistent with semi-analytical equations that describe orbits in binary systems. In the observations we also find tentative evidence of a circumtertiary ring that could be edge-on.