Hydrodynamical Simulations of Misaligned Accretion Discs in Binary Systems: Companions tear discs

Proceedings of the International Astronomical Union, vol. 16, pp. 177–183

Abstract

Abstract Accretion discs appear in many astrophysical systems. In most cases, these discs are probably not completely axisymmetric. Discs in binary systems are often found to be misaligned with respect to the binary orbit. In this case, the gravitational torque from a companion induces nodal precession in misaligned rings of gas. We first calculate whether this precession is strong enough to overcome the internal disc torques communicating angular momentum. For typical parameters, precession torque wins. To check this result, we perform numerical simulations using the Smoothed Particle Hydrodynamics code, PHANTOM, and confirm that sufficiently thin and sufficiently inclined discs can break into distinct planes that precess effectively independently. Disc tearing is widespread and severely changes the disc structure. It enhances dissipation and promotes stronger accretion onto the central object. We also perform a stability analysis on isolated warped discs to understand the physics of disc breaking and tearing observed in numerical simulations. The instability appears in the form of viscous anti-diffusion of the warp amplitude and the surface density. The discovery of disc breaking and tearing has revealed new physical processes that dramatically change the evolution of accretion discs, with obvious implications for observed systems.

Authors 5

1. Suzan Doğan

   Ege University

   Affiliation as printed

   Department of Astronomy & Space Sciences, University of Ege, Bornova, İzmir, Turkey

2. C. J. Nixon

   University of Leicester

   Affiliation as printed

   Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK

3. Andrew R. King Aachen Leiden Observatory

   Leiden University · University of Leicester · Leiden Observatory · University of Amsterdam

   Affiliation as printed

   Anton Pannekoek Institute, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, Netherlands

   Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK

   Leiden Observatory, Leiden University, Niels Bohrweg 2, NL-2333 CA Leiden, Netherlands

4. J. E. Pringle

   University of Leicester · University of Cambridge

   Affiliation as printed

   Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK

   Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA, UK

5. Daniel J. Price

   Monash University

   Affiliation as printed

   Monash Centre for Astrophysics (MoCA), School of Mathematical Sciences, Monash University, Vic. 3800, Australia