Grid-Based Simulations of Polar Aligned Protoplanetary Disks

Young binary star systems such as HD 98800 and IRS 43 have recently been observed with circumbinary disks aligned perpendicular to the binary plane, suggesting a potentially new population of polar-orbiting circumbinary planets. To study the formation of these planets, we simulate the evolution of an inclined disk around an eccentric binary using the grid-based code ATHENA++. Our simulations explore lower viscosities than have previously been studied. We find alignment towards a polar orientation, in agreement with previous studies. At low viscosities, anticyclonic vortices are observed along the inner edge of the disk which are long lived and generate overdensity features and spiral arms. The torque exerted by the binary also warps the disk and can cause the disk to break. We study the propagation of these warps and confirm the warp evolution in the diffusive and bending wave regimes, and also give estimates for the disk breaking radius. Finally, we discuss the importance of these features to a broader range of topics such as episodic accretion systems, the formation of circumbinary planets, and the final evolution of black hole binaries.