Dynamical Mass of the Exoplanet Host Star HR 8799
Abstract

HR 8799 is a young A5/F0 star hosting four directly imaged giant planets at wide separations (∼16–78 au), which are undergoing orbital motion and have been continuously monitored with adaptive optics imaging since their discovery over a decade ago. We present a dynamical mass of HR 8799 using 130 epochs of relative astrometry of its planets, which include both published measurements and new medium-band 3.1μm observations that we acquired with NIRC2 at Keck Observatory. For the purpose of measuring the host-star mass, each orbiting planet is treated as a massless particle and is fit with a Keplerian orbit using Markov chain Monte Carlo. We then use a Bayesian framework to combine each independent total mass measurement into a cumulative dynamical mass using all four planets. The dynamical mass of HR 8799 is$1.47−0.17+0.12$Massuming a uniform stellar mass prior, or$1.46−0.15+0.11$Mwith a weakly informative prior based on spectroscopy. There is a strong covariance between the planets’ eccentricities and the total system mass; when the constraint is limited to low-eccentricity solutions ofe< 0.1, which are motivated by dynamical stability, our mass measurement improves to$1.43−0.07+0.06$M. Our dynamical mass and other fundamental measured parameters of HR more »

Authors:
;
Publication Date:
NSF-PAR ID:
10363242
Journal Name:
The Astronomical Journal
Volume:
163
Issue:
2
Page Range or eLocation-ID:
Article No. 52
ISSN:
0004-6256
Publisher:
DOI PREFIX: 10.3847
National Science Foundation
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