A study of the orbits of the logarithmic potential for galaxies

ABSTRACT The logarithmic potential is of great interest and relevance in the study of the dynamics of galaxies. Some small corrections to the work of Contopoulos & Seimenis who used the method of Prendergast to find periodic orbits and bifurcations within such a potential are presented. The solution of the orbital radial equation for the purely radial logarithmic potential is then considered using the precessing ellipse (p-ellipse) method pioneered by Struck. This differential orbital equation is a special case of the generalized Burgers equation. The apsidal angle is also determined, both numerically and analytically by means of the Lambert W and the polylogarithmic functions. The use of these functions in computing the gravitational lensing produced by logarithmic potentials is discussed