  This is the second of two papers where we study additional analytical
solutions of a bidimensional low mass gaseous disc rotating around a central
mass and submitted to small radial perturbations. In a first Paper,
hydrodynamics equations were solved for the equilibrium and perturbed
configurations and a wave-like equation for the gas perturbed specific mass was
deduced and solved analytically for several cases of exponents of the power law
distributions of the unperturbed specific mass and sound speed. In this paper,
two other general cases of exponents, including a polytropic case, are solved
analytically for small frequencies of the perturbations. Similar conclusions to
the ones of Paper I are found, namely that the maxima of the gas perturbed
specific mass are exponentially spaced and that their distance ratio is a
constant, function of disc characteristics and of the perturbations frequency.
Gaseous annular structures would eventually be formed in the disc by inward and
outward gas flows from zones of minima toward zones of maxima of perturbed
specific mass.
