Spherical Accretion onto Neutron Stars Revisited: Are Hot Solutions   Possible ?
  Stationary, spherical accretion onto an unmagnetized neutron star is here reconsidered on the wake of the seminal paper by Zel'dovich \& Shakura (1969). It is found that new ``hot'' solutions may exist for a wide range of luminosities. These solutions are characterized by a high temperature, $10^{9}\div 10^{11}$ K, and arise from a stationary equilibrium model where the dominant radiative mechanisms are multiple Compton scattering and bremsstrahlung emission. For low luminosities, $\mincir 10^{-2} \ L_{E}$, only the ``cold'' (\`a la Zel'dovich and Shakura) solution is present. 
Roberto Turolla, Luca Zampieri, Monica Colpi and Aldo Treves