High-contrast, high-angular resolution view of the GJ 367 exoplanet system
ABSTRACT

We search for additional companions in the GJ 367 exoplanet system and aim to better constrain its age and evolutionary status. We analyse high-contrast direct imaging observations obtained with HST/NICMOS, VLT/NACO, and VLT/SPHERE. We investigate and critically discuss conflicting age indicators based on theoretical isochrones and models for Galactic dynamics. A comparison of GAIA EDR3 parallax and photometric measurements with theoretical isochrones suggests a young age ≤60 Myr for GJ 367. The star’s Galactic kinematics exclude membership to any nearby young moving group or stellar stream. Its highly eccentric Galactic orbit, however, is atypical for a young star. Age estimates considering Galactic dynamical evolution are most consistent with an age of 1–8 Gyr. We find no evidence for a significant mid-infrared excess in the WISE bands, suggesting the absence of warm dust in the GJ 367 system. The direct imaging data provide significantly improved detection limits compared to previous studies. At 530 mas (5 au) separation, the SPHERE data achieve a 5σ contrast of 2.6 × 10−6. The data exclude the presence of a stellar companion at projected separations ≥0.4 au. At projected separations ≥5 au we can exclude substellar companions with a mass ≥1.5 MJup for an age of 50 Myr, and ≥20 MJup for an age of 5 Gyr. By applying the more »

Authors:
;  ;  ;
Publication Date:
NSF-PAR ID:
10366628
Journal Name:
Monthly Notices of the Royal Astronomical Society
Volume:
513
Issue:
1
Page Range or eLocation-ID:
p. 661-669
ISSN:
0035-8711
Publisher:
Oxford University Press
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 HRmore »