N-body Interactions will be Detectable in the HR-8799 System within 5 years with VLTI-GRAVITY

TL;DR

This paper demonstrates that the VLTI-GRAVITY instrument can detect N-body interactions in the HR-8799 system within five years, enabling direct measurement of exoplanet masses through high-precision astrometry.

Contribution

It shows that interferometric astrometry with VLTI-GRAVITY can detect planet-planet interactions in HR-8799, allowing direct mass constraints for exoplanets.

Findings

N-body deviations up to 0.25 milliarcseconds predicted within five years.

VLTI-GRAVITY's precision enables detection of these deviations.

Modeling of HR-8799 is essential for accurate mass determination.

Abstract

While Keplerian orbits account for the majority of the astrometric motion of directly-imaged planets, perturbations due to N-body interactions allow us to directly constrain exoplanet masses in multiplanet systems. This has the potential to improve our understanding of massive directly-imaged planets, which nearly all currently have only model-dependent masses. The VLTI-GRAVITY instrument has demonstrated that interferometry can achieve 100x better astrometric precision (Gravity Collaboration et al. 2019) than existing methods, a level of precision that makes detection of planet-planet interactions possible. In this study, we show that in the HR-8799 system, planet-planet deviations from currently used Keplerian approximations (Lacour et al. 2021) are expected to be up to one-quarter of a milliarc-second within five years, which will make them detectable with VLTI-GRAVITY. Modeling of this system to directly constrain exoplanet masses will be crucial in order to make precise predictions.