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

Annular structures in perturbed low mass disc-shaped gaseous nebulae II : general and polytropic models