Exact equilibria of a stellar system in a linearised tidal field

Abstract

We study the motion of stars in a star cluster which revolves in a circular orbit about its parent galaxy. The star cluster is modelled as an ellipsoid of uniform spatial density. We exhibit two 2-parameter families of self-consistent equilibrium models in which the velocity at each point is confined to a line in velocity space. We exhibit the link between this problem and that of a uniform rotating ellipsoidal galaxy. With minimal adaptation, Freeman's bar models yield a third family.