Nonuniqueness of stationary accretion in the Shakura model
  We investigate the accretion onto luminous bodies with hard surfaces within the framework of newtonian theory. The accreting gases are assumed to be polytropes and their selfgravitation is included. A remarkable feature of the model is that under proper boundary conditions some parameters of the sonic point are the same as in the Bondi model and the relation between luminosity and the gas abundance reduces to an algebraic relation. All that holds under assumptions of stationarity and spherical symmetric. Assuming data that are required for the complete specification of the system, one finds that generically for a given luminosity there exist two solutions with different compact cores. 
Edward Malec and Krzysztof Roszkowski