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

Journal article, 2016

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, to learn more about the 94 Ceti system, we aim to model the dust emission precisely to fit its observed spectral energy distribution 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-fitting 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 simulation 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.