A new code to study structures in collisionally active, perturbed debris discs: application to binaries

LESIA-Observatoire de Paris, CNRS, UPMC Univ. Paris 06, Univ. Paris-Diderot, France
e-mail: philippe.thebault@obspm.fr

Received: 17 August 2011
Accepted: 17 October 2011

Abstract

Context. Debris discs are traditionally studied using two distinct types of numerical models: statistical particle-in-a-box codes to study their collisional and size distribution evolution, and dynamical N-body models to study their spatial structure. The absence of collisions in N-body codes is in particular a major shortcoming, as collisional processes are expected to significantly alter the results obtained from pure N-body runs.

Aims. We present a new numerical model, to study the spatial structure of perturbed debris discs in both a dynamical and collisional steady-state. We focus on the competing effects of gravitational perturbations by a massive body (planet or star), the collisional production of small grains, and the radiation pressure placing these grains in possibly dynamically unstable regions.

Methods. We consider a disc of parent bodies in a dynamical steady-state, from which small radiation-pressure-affected grains are released in a series of runs, each corresponding to a different orbital position of the perturber, where particles are assigned a collisional destruction probability. These collisional runs produce successive position maps that are then recombined, following a complex procedure, to generate surface density profiles for each orbital position of the perturbing body.

Results. We apply our code to the case of a circumprimary disc in a binary. We find pronounced structures inside and outside the dynamical stability regions. For low e_B, the disc’s structure is time varying, with spiral arms in the dynamically “forbidden” region precessing with the companion star. For high e_B, the disc is strongly asymmetric but time invariant, with a pronounced density drop in the binary’s periastron direction.