Constraining the Circumbinary Disk Tilt in the KH 15D system

TL;DR

This paper models the KH 15D system's circumbinary disk, fitting 60 years of photometric data to constrain its tilt, structure, and precession, revealing a misaligned, warped disk with specific inner and outer edges.

Contribution

The study presents a self-consistent model of the KH 15D circumbinary disk, providing new constraints on its tilt, warp, and precession based on long-term photometric observations.

Findings

Disk inner edge $r_{in} \,\lesssim\, 1$ au

Disk outer edge $r_{out} \sim$ a few au

Disk misaligned by 5-16 degrees with warp and twist features

Abstract

KH 15D is a system which consists of a young, eccentric binary, and a circumbinary disk which obscures the binary as the disk 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 years. Our model suggests that the circumbinary disk has an inner edge $r_{\rm in}\lesssim 1 \ {\rm au}$, an outer edge $r_{\rm out} \sim {\rm a \ few \ au}$, and that the disk is misaligned relative to the stellar binary by $\sim$5-16 degrees, 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 disk are of order $\sim$10 degrees and $\sim$15 degrees, respectively. We also provide constraints on other properties of the disk, 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 disks.