Neutrino‐driven Jets and Rapid‐Process Nucleosynthesis

We have studied whether the jet in a collapse-driven supernova can be a keyprocess for the rapid-process (r-process) nucleosynthesis. We have examined thefeatures of a steady, subsonic, and rigidly rotating jet in which thecentrifugal force is balanced by the magnetic force. As for the models in whichthe magnetic field is weak and angular velocity is small, we found that ther-process does not occur because the final temperature is kept to be too highand the dynamical timescale becomes too long when the neutrino luminosities areset to be high. Even if the luminosities of the neutrinos are set to be low,which results in the low final temperature, we found that the models do notgive a required condition to produce the r-process matter. Furthermore, theamount of the mass outflow seems to be too little to explain the solar-systemabundance ratio in such low-luminosity models. As for the models in which themagnetic field is strong and angular velocity is large, we found that theentropy per baryon becomes too small and the dynamical timescale becomes toolong. This tendency is, of course, a bad one for the production of ther-process nuclei. As a conclusion, we have to say that it is difficult to causea successful r-process nucleosynthesis in the jet models in this study.Comment: 34 pages and 6 postscript figures. submitted to Astrophysical Journa