Dynamics of the young multiple system GG Tauri

I. Orbital fits and inner edge of the circumbinary disk of GG Tau A

¹ Laboratoire d'Astrophysique de Grenoble, Université J. Fourier, UMR 5571 du CNRS, BP 53, 38041 Grenoble Cedex 9, France e-mail: herve.beust@obs.ujf-grenoble.fr
² Laboratoire d'Astrodynamique, d'Astrophysique et d'Aéronomie de Bordeaux, 2 rue de l'Observatoire, BP 89, 33270 Floirac, France

Received: 26 November 2004
Accepted: 1 April 2005

Abstract

The GG Tauri system is a prototype example of a young, pre-main sequence multiple stellar system. Both millimeter and optical observations reveal that the central binary (GG Tau A) harbors a ring-shape circumbinary disk. In this paper, we analyse a compilation of astrometric data of the GG Tau A binary over 12 years that allow us, in combination with information coming from the disk observations (millimeter data), to derive a fairly accurate fit of the orbit (AU, ). We also perform a dynamical study of the circumbinary disk, and show that in order to be in agreement with the orbit deduced from the fit, the inner gap of the disk should be approximatively twice as small as observed. We show that if we allow the error bars on the astrometric data to be larger, another orbit may be found (AU, ), compatible with the location of the inner disk gap, although only marginally compatible with the astrometric data. Possible solutions to solve this discrepancy are discussed.