The Orbit of GG Tau A

TL;DR

This study investigates the orbit of the binary system GG Tau A and its relation to the circumbinary disk, revealing that the orbit likely causes the disk gap only if there is a misalignment or measurement errors.

Contribution

The paper combines new and existing astrometric data to model the orbit of GG Tau A and explores its potential role in shaping the disk structure.

Findings

Coplanar orbit models are too small to explain the disk gap.

Larger orbit models are tilted relative to the disk.

Misalignment or measurement errors may explain the gap formation.

Abstract

We present a study of the orbit of the pre-main-sequence binary system GG Tau A and its relation to its circumbinary disk, in order to find an explanation for the sharp inner edge of the disk. Three new relative astrometric positions of the binary were obtained with NACO at the VLT. We combine these with data from the literature and fit orbit models to the dataset. We find that an orbit coplanar with the disk and compatible with the astrometric data is too small to explain the inner gap of the disk. On the other hand, orbits large enough to cause the gap are tilted with respect to the disk. If the disk gap is indeed caused by the stellar companion, then the most likely explanation is a combination of underestimated astrometric errors and a misalignment between the planes of the disk and the orbit.