Abstract: Debris disks are collections of dust around main sequence stars, formed through collisions of planetesimals such as comets and asteroids. Although debris disks are common, only a handful of systems include a disk as well as a directly imaged planet. HD 106906 is a short-period stellar binary, host to an 11 Mjup planet, HD 106906b, at a separation of 735 au and a debris disk, which has been resolved at optical and radio wavelengths. We resolve the structure in the disk at a wavelength of 1.3 mm with the Atacama Large Millimeter/submillimeter Array (ALMA) at a resolution of .31” (30 au). An analysis of our data supports a disk that is symmetrical in surface brightness at this wavelength, with moderate evidence for an offset between the center of the disk and the expected position of the stellar binary (δx = 19±6 au). We then use dynamical theory to compare astrometric constraints on the planet’s orbit (Nguyen et al. 2021) and scattered light morphology (Krotts et al. 2021) with the observed disk morphology. The stellar offset in the ALMA data might indicate an eccentric disk, consistent with studies by HST and the Gemini Planet Imager (GPI). However, a truly eccentric disk would result in asymmetrical surface brightness as well which is not observed in the ALMA data. The disk is both more symmetric and vertically thinner than would be expected if the scattered light asymmetry were induced by a highly elliptical and inclined orbit for HD 106906b. Instead, it seems more likely that the planet’s orbit is large and low-eccentricity, which would explain the large offset from the star, the small vertical height, and the symmetry of the disk observed with ALMA.
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