The r-Process Nucleosynthesis in Neutrino-/Magnetocentrifugally-Driven Winds

We have studied whether the rotation and magnetic fields in neutrino-drivenwinds can be key processes for the rapid-process (r-process) nucleosynthesis.We have examined the features of a steady and subsonic wind solutions whichextend the model of Weber and Davis (1967), which is a representative solarwind model. As a result, we found that the entropy per baryon becomes lower andthe dynamical timescale becomes longer as the angular velocity becomes higher.These results are inappropriate for the production of the r-process nuclei. Asfor the effects of magnetic fields, we found that a solution as a steady windfrom the surface of the proto-neutron star can not be obtained when thestrength of the magnetic field becomes $\ge$ $10^{11}$ G. Since the magneticfield in normal pulsars is of order $10^{12}$ G, a steady wind solution mightnot be realized there, which means that the models in this study may not beadopted for normal proto-neutron stars. In this situation, we have littlechoice but to conclude that it is difficult to realize a successful r-processnucleosynthesis in the wind models in this framework.Comment: 20 pages and 4 postscript figures. submitted to Publications of the Astronomical Society of Japa