First detection of orbital motion for HD 106906 b: A wide-separation exoplanet on a Planet Nine-like orbit

Abstract

HD 106906 is a 15 Myr old short-period (49 days) spectroscopic binary that hosts a wide-separation (737 au) planetary-mass ($\sim 11M_{\mathrm{Jup}}$) common proper motion companion, HD 106906 b. Additionally, a circumbinary debris disk is resolved at optical and near-infrared wavelengths that exhibits a significant asymmetry at wide separations that may be driven by gravitational perturbations from the planet. In this study we present the first detection of orbital motion of HD 106906 b using Hubble Space Telescope images spanning a 14 yr period. We achieve high astrometric precision by cross-registering the locations of background stars with the Gaia astrometric catalog, providing the subpixel location of HD 106906 that is either saturated or obscured by coronagraphic optical elements. We measure a statistically significant $31.8\pm 7.0$ mas eastward motion of the planet between the two most constraining measurements taken in 2004 and 2017. This motion enables a measurement of the inclination between the orbit of the planet and the inner debris disk of either $36_{-14}^{+27}$ deg or $44_{-14}^{+27}$ deg, depending on the true orientation of the orbit of the planet. There is a strong negative correlation between periastron and mutual inclination; orbits with smaller periastra are more misaligned with the disk plane. With a periastron of $510_{-320}^{+480}$ au, HD 106906 b is likely detached from the planetary region within 100 au radius, showing that a Planet Nine-like architecture can be established very early in the evolution of a planetary system.

38 pages, 14 figures. Published in The Astronomical Journal on December 10, 2020

References in corpus (13)

• The Planet Nine Hypothesis
• orbitize!: A Comprehensive Orbit-fitting Software Package for the High-contrast Imaging Community
• Reconnaissance of the HR 8799 Exosolar System II: Astrometry and Orbital Motion
• Evidence for a high mutual inclination between the cold Jupiter and transiting super Earth orbiting $\pi$ Men
• A precise architecture characterization of the $\pi$ Men planetary system
• Investigating the flyby scenario for the HD 141569 system
• An ALMA and MagAO Study of the Substellar Companion GQ Lup B
• A significant mutual inclination between the planets within the $\pi$ Mensae system
• Dynamical Evidence of a Spiral Arm--Driving Planet in the MWC 758 Protoplanetary Disk
• Rigorous treatment of barycentric stellar motion: Perspective and light-time effects in astrometric and radial velocity data
• HD 106906: A Case Study for External Perturbations of a Debris Disk
• A Near-coplanar Stellar Flyby of the Planet Host Star HD 106906
• HD 165054: an astrometric calibration field for high-contrast imagers in Baade's Window

Cited by in corpus (8)

• Rotation Periods, Inclinations, and Obliquities of Cool Stars Hosting Directly Imaged Substellar Companions: Spin-Orbit Misalignments are Common
• A wide-orbit giant planet in the high-mass b Centauri binary system
• Stellar Flyby Analysis for Spiral Arm Hosts with Gaia DR3
• Giant Impacts and Debris Disk Morphology
• Millimeter Dust Emission and Planetary Dynamics in the HD 106906 System
• Search for Stellar Flybys in the Sco-Cen OB Association with the Gaia DR2
• Memories of past close encounters in extreme trans-Neptunian space: Finding unseen planets using pure random searches
• Obliquity Constraints on the Planetary-mass Companion HD 106906 b