ON THE POTENTIAL-DENSITY RELATION FOR STACKEL DISCS

The general form of the surface density of an infinitely thin disc is given that generates a Stackel potential in the disc only, using formu lae for the potential of elliptic and hyperbolic strings. This is usef ul for problems in which a simple form for the potential is important, while the corresponding surface density need only be known to check ( numerically) that it is positive. A simple potential with a positive s urface density is given. Also, formulae are given to calculate the sur face density of such a Stackel disc, in the case in which the rotation curve is given and all the mass is concentrated in the disc.