Constraining the circumbinary disc tilt in the KH 15D system

Abstract

KH 15D is a system that consists of a young, eccentric binary, and a circumbinary disc that obscures the binary as the disc precesses. We develop a self-consistent model that provides a reasonable fit to the photometric variability that was observed in the KH 15D system over the past 60 yr. Our model suggests that the circumbinary disc has an inner edge rin ≲ 1 au, an outer edge rout ∼ a few au, and that the disc is misaligned relative to the stellar binary by ∼5-16◦, with the inner edge more inclined than the outer edge. The difference between the inclinations (warp) and longitude of ascending nodes (twist) at the inner and outer edges of the disc are of order ∼10 and ∼15◦, respectively. We also provide constraints on other properties of the disc, such as the precession period and surface density profile. Our work demonstrates the power of photometric data in constraining the physical properties of planet-forming circumbinary discs.