On the eccentricity of self-gravitating circumstellar disks in eccentric binary systems

¹ Dipartimento di Fisica, University of Padova, Via Marzolo 8, 35131 Padova, Italy e-mail: marzari@pd.infn.it
² Laboratoire Cassiopée, Université de Nice Sophia Antipolis, CNRS, Observatoire de la Côte d'Azur, BP 4229, 06304 Nice Cedex, France
³ Observatoire de Paris, Section de Meudon, 92195 Meudon Principal Cedex, France
⁴ Astronomy and Astrophysics Department, University of California, Santa Cruz, CA 95064, USA

Received: 1 April 2009
Accepted: 3 August 2009

Abstract

Aims. We study the evolution of circumstellar massive disks around the primary star of a binary system focusing on the computation of disk eccentricity. In particular, we concentrate on its dependence on the binary eccentricity. Self-gravitation is included in our numerical simulations. Our standard model assumes a semimajor axis for the binary of 30 AU, the most probable value according to the present binary statistics.

Methods. Two-dimensional hydrodynamical computations are performed with FARGO. Besides the dynamical standard method to determine disk eccentricities, we apply a morphological method which may allow a better comparison with observations.

Results. Self-gravitation leads to disks that, on average, have low eccentricity. Moreover, the orientation of the disk computed with the standard dynamical method always librates instead of circulating as in simulations without self-gravitation. The disk eccentricity decreases with the binary eccentricity, a result found also in models without self-gravitation.

Conclusions. Disk self-gravitation appears to be an important factor in determining the evolution of a massive disk in a binary system. High eccentricity binaries are not necessarily a hostile environment for planetary accretion.