Millimeter Dust Emission and Planetary Dynamics in the HD 106906 System

Abstract Debris disks are dusty, optically thin structures around main-sequence stars. HD 106906AB is a short-period stellar binary, host to a wide-separation planet, HD 106906b, and a debris disk. Only a few known systems include a debris disk and a directly imaged planet, and HD 106906 is the only...

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Published in:	The Astrophysical journal 2022-11, Vol.939 (1), p.56
Main Authors:	Fehr, Anna J., Hughes, A. Meredith, Dawson, Rebekah I., Marino, Rachel E., Ackelsberg, Matan, Kittling, Jamar, Flaherty, Kevin M., Nesvold, Erika, Carpenter, John, Andrews, Sean M., Matthews, Brenda, Crotts, Katie, Kalas, Paul
Format:	Article
Language:	eng
Subjects:	Accretion disks Astrophysics Asymmetry Binary stars Circumstellar disks Debris Debris disks Detritus Dust Dust content Dust emission Exoplanet dynamics Exoplanet formation Gravitational instability Main sequence stars Millimeter astronomy Orbital stability Planetary orbits Planets Radio telescopes Separation
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Summary:	Abstract Debris disks are dusty, optically thin structures around main-sequence stars. HD 106906AB is a short-period stellar binary, host to a wide-separation planet, HD 106906b, and a debris disk. Only a few known systems include a debris disk and a directly imaged planet, and HD 106906 is the only one in which the planet is exterior to the disk. The debris disk is edge-on and highly asymmetric in scattered light. Here we resolve the disk structure at a resolution of 0.″38 (39 au) with the Atacama Large Millimeter/submillimeter Array (ALMA) at a wavelength of 1.3 mm. We model the disk with both a narrow and broad ring of material, and find that a radially broad, axisymmetric disk between radii of ∼50–100 au is able to capture the structure of the observations without evidence of any asymmetry or eccentricity, other than a tentative stellocentric offset. We place stringent upper limits on both the gas and dust contents of a putative circumplanetary disk. We interpret the ALMA data in concert with scattered-light observations of the inner ring and astrometric constraints on the planet’s orbit, and find that the observations are consistent with a large-separation, low-eccentricity orbit for the planet. A dynamical analysis indicates that the central binary can efficiently stabilize planetesimal orbits interior to ∼100 au, which somewhat relaxes the constraints on the eccentricity and semimajor axis. The observational constraints are consistent with in-situ formation via gravitational instability but cannot rule out a scattering event as the origin for HD 106906b’s current orbit.
ISSN:	0004-637X 1538-4357