# GG Tau A: Dark shadows on the ringworld

## TL;DR

This study uses radiative transfer simulations to analyze how circumstellar disks around GG Tau A influence the observed scattered light, revealing shadowing effects and disk misalignments that shape the circumbinary disk's appearance.

## Contribution

It demonstrates that the observed features of GG Tau A's circumbinary disk are caused by shadowing from misaligned circumstellar disks, providing new insights into disk geometry and star-disk interactions.

## Key findings

- The circumbinary disk is in the shadow of at least two co-planar circumstellar disks.
- The inner wall of the circumbinary disk is heavily obscured at the midplane.
- The dark lane is caused by self-shadowing from a misaligned circumstellar disk.

## Abstract

Context. With its high complexity, large size, and close distance, the ringworld around GG Tau A is an appealing case to study the formation and evolution of protoplanetary disks around multiple star systems. However, investigations with radiative transfer models are usually neglecting the influence of the circumstellar dust around the individual stars. Aims. We investigate how circumstellar disks around the stars of GG Tau A are influencing the emission that is scattered at the circumbinary disk and if constraints on these circumstellar disks can be derived. Methods. We perform radiative transfer simulations with the code POLARIS to obtain spectral energy distributions and emission maps in the H-Band (near-infrared). Subsequently, we compare them with observations to achieve our aims. Results. We studied the ratio of polarized intensity at different locations in the circumbinary disk and conclude that the observed scattered-light near-infrared emission is best reproduced, if the circumbinary disk lies in the shadow of at least two co-planar circumstellar disks surrounding the central stars. This implies that the inner wall of the circumbinary disk is strongly obscured around the midplane, while the observed emission is actually dominated by the most upper disk layers. In addition, the inclined dark lane ("gap") on the western side of the circumbinary disk, which is a stable (non rotating) feature since ~20yr, can only be explained by the self-shadowing of a misaligned circumstellar disk surrounding one of the two components of the secondary close-binary star GG Tau Ab.