Obliquity Constraints on the Planetary-mass Companion HD 106906 b

We constrain the angular momentum architecture of HD 106906, a 13 ± 2 Myr old system in the ScoCen complex composed of a compact central binary, a widely separated planetary-mass tertiary HD 106906 b, and a debris disk nested between the binary and tertiary orbital planes. We measure the orientation...

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Bibliographic Details
Published in:The Astronomical journal 2021-11, Vol.162 (5), p.217
Main Authors: Bryan, Marta L., Chiang, Eugene, Morley, Caroline V., Mace, Gregory N., Bowler, Brendan P.
Format: Article
Language:English
Subjects:
Angular momentum
Astronomy
Astrostatistics
Exoplanet astronomy
Exoplanet evolution
Exoplanet formation
Exoplanet systems
Extrasolar planets
Gravitational instability
High resolution spectroscopy
Misalignment
Obliquity
Rotation
Rotational spectra
Tertiary
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Summary:We constrain the angular momentum architecture of HD 106906, a 13 ± 2 Myr old system in the ScoCen complex composed of a compact central binary, a widely separated planetary-mass tertiary HD 106906 b, and a debris disk nested between the binary and tertiary orbital planes. We measure the orientations of three vectors: the companion spin axis, companion orbit normal, and disk normal. Using near-IR high-resolution spectra from Gemini/IGRINS, we obtain a projected rotational velocity of v sin i p = 9.5 ± 0.2 km s −1 for HD 106906 b. This measurement together with a published photometric rotation period implies the companion is viewed nearly pole-on, with a line-of-sight spin axis inclination of i p = 14° ± 4° or 166° ± 4°. By contrast, the debris disk is known to be viewed nearly edge on. The likely misalignment of all three vectors suggests HD 106906 b formed by gravitational instability in a turbulent environment, either in a disk or cloud setting.
ISSN:0004-6256
1538-3881
DOI:10.3847/1538-3881/ac1bb1