A Near-coplanar Stellar Flyby of the Planet Host Star HD 106906

Abstract

We present an investigation into the kinematics of HD 106906 using the newly released Gaia DR2 catalog to search for close encounters with other members of the Scorpius-Centaurus (Sco-Cen) association. HD 106906 is an eccentric spectroscopic binary that hosts both a large asymmetric debris disk extending out to at least 500 au and a directly imaged planetary-mass companion at a projected separation of 738 au. The cause of the asymmetry in the debris disk and the unusually wide separation of the planet is not currently known. Using a combination of Gaia DR2 astrometry and ground-based radial velocities, we explore the hypothesis that a close encounter with another cluster member within the last 15 Myr is responsible for the present configuration of the system. Out of 461 stars analyzed, we identified two candidate perturbers that had a median closest approach (CA) distance within 1 pc of HD 106906: HIP 59716 at $D_{\mathrm{CA}}=0.65_{-0.40}^{+0.93}$ pc ($t_{\mathrm{CA}}=-3.49_{-1.76}^{+0.90}$ Myr) and HIP 59721 at $D_{\mathrm{CA}}=0.71_{-0.11}^{+0.18}$ pc ($t_{\mathrm{CA}}=-2.18_{-1.04}^{+0.54}$ Myr), with the two stars likely forming a wide physical binary. The trajectories of both stars relative to HD 106906 are almost coplanar with the inner disk ($\Delta \theta =5.4\pm 1.7$ deg and $4.2_{-1.1}^{+0.9}$ deg). These two stars are the best candidates of the currently known members of Sco-Cen for having a dynamically important close encounter with HD 106906, which may have stabilized the orbit of HD 106906 b in the scenario where the planet formed in the inner system and attained high eccentricity by interaction with the central binary.

10 pages, 6 figures, accepted for publication in AJ

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Cited by in corpus (17)

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• Trajectory of the stellar flyby that shaped the outer solar system
• A Wide Planetary Mass Companion Discovered Through the Citizen Science Project Backyard Worlds: Planet 9
• Stellar Flyby Analysis for Spiral Arm Hosts with Gaia DR3
• The case of HD 106906 debris disc: A binary's revenge
• A Deep Polarimetric Study of the Asymmetrical Debris Disk HD 106906
• Running with the Bulls: The frequency of star-disc encounters in the Taurus star forming region
• Planet population synthesis: The role of stellar encounters
• ALMA imaging of the M-dwarf Fomalhaut C's debris disc
• Flybys in debris disk systems with Gaia eDR3
• Formation History of HD106906 and the Vertical Warping of Debris Disks by an External Inclined Companion
• 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
• Radial velocity analysis of stars with debris discs
• Obliquity Constraints on the Planetary-mass Companion HD 106906 b