Constraints on the architecture of the HD 95086 planetary system with the Gemini Planet Imager

TL;DR

This study uses Gemini Planet Imager data to monitor the exoplanet HD 95086 b, constraining its orbit and discussing the implications for additional planets shaping the debris disk.

Contribution

First orbital constraints for HD 95086 b using astrometric data and Monte Carlo methods, informing models of the planetary system architecture.

Findings

Orbital inclination of approximately 153 degrees.

Semimajor axis around 62 au with uncertainties.

Eccentricity less than 0.21.

Abstract

We present astrometric monitoring of the young exoplanet HD 95086 b obtained with the Gemini Planet Imager between 2013 and 2016. A small but significant position angle change is detected at constant separation; the orbital motion is confirmed with literature measurements. Efficient Monte Carlo techniques place preliminary constraints on the orbital parameters of HD 95086 b. With 68% confidence, a semimajor axis of 61.7^{+20.7}_{-8.4} au and an inclination of 153.0^{+9.7}_{-13.5} deg are favored, with eccentricity less than 0.21. Under the assumption of a co-planar planet-disk system, the periastron of HD 95086 b is beyond 51 au with 68% confidence. Therefore HD 95086 b cannot carve the entire gap inferred from the measured infrared excess in the SED of HD 95086. We use our sensitivity to additional planets to discuss specific scenarios presented in the literature to explain the geometry of the debris belts. We suggest that either two planets on moderately eccentric orbits or three to four planets with inhomogeneous masses and orbital properties are possible. The sensitivity to additional planetary companions within the observations presented in this study can be used to help further constrain future dynamical simulations of the planet-disk system.