(\beta\) Pictoris' inner disk in polarized light and new orbital parameters for \(\beta\) Pictoris b

We present \(H\)-band observations of \(\beta\) Pic with the Gemini Planet Imager's (GPI's) polarimetry mode that reveal the debris disk between ~0.3" (~6 AU) and ~1.7" (~33 AU), while simultaneously detecting \(\beta\) Pic \(b\). The polarized disk image was fit with a dust density model combined with a Henyey-Greenstein scattering phase function. The best fit model indicates a disk inclined to the line of sight (\(\phi=85.27{\deg}^{+0.26}_{-0.19}\)) with a position angle \(\theta_{PA}=30.35{\deg}^{+0.29}_{-0.28}\) (slightly offset from the main outer disk, \(\theta_{PA}\approx29{\deg}\)), that extends from an inner disk radius of \(23.6^{+0.9}_{-0.6}\) AU to well outside GPI's field of view. In addition, we present an updated orbit for \(\beta\) Pic \(b\) based on new astrometric measurements taken in GPI's spectroscopic mode spanning 14 months. The planet has a semi-major axis of \(a=9.2^{+1.5}_{-0.4}\)AU, with an eccentricity \(e\leq 0.26\). The position angle of the ascending node is \(\Omega=31.75{\deg}\pm0.15\), offset from both the outer main disk and the inner disk seen in the GPI image. The orbital fit constrains the stellar mass of \(\beta\) Pic to \(1.60\pm0.05 M_{\odot}\). Dynamical sculpting by \(\beta\) Pic \(b\) cannot easily account for the following three aspects of the inferred disk properties: 1) the modeled inner radius of the disk is farther out than expected if caused by \(\beta\) Pic b; 2) the mutual inclination of the inner disk and \(\beta\) Pic \(b\) is \(4{\deg}\), when it is expected to be closer to zero; and 3) the aspect ratio of the disk (\(h_0 = 0.137^{+0.005}_{-0.006}\)) is larger than expected from interactions with \(\beta\) Pic \(b\) or self-stirring by the disk's parent bodies.