We present a simplified analysis using equations for the charge flow , which include \nu _ { e } capture , for the production of r -process nuclei in the context of the recent supernova hot bubble model .
The role of \nu _ { e } capture in speeding up the charge flow , particularly at the closed neutron shells , is studied together with the \beta -flow at freeze-out and the effect of neutrino-induced neutron emission on the abundance pattern after freeze-out .
It is shown that a semi-quantitative agreement with the gross solar r -process abundance pattern from the peak at mass number A \sim 130 , through the peak at A \sim 195 , and up to the region of the actinides can be obtained by a superposition of two distinctive kinds of r -process events .
These correspond to a low frequency case L and a high frequency case H , which takes into account the low abundance of ^ { 129 } I and the high abundance of ^ { 182 } Hf in the early solar nebula .
The lifetime of ^ { 182 } Hf ( \tau _ { 182 } \approx 1.3 \times 10 ^ { 7 } yr ) associates the events in case H with the most common Type II supernovae .
These events would be mainly responsible for the r -process nuclei near and above A \sim 195 .
They would also make a significant amount of the nuclei between A \sim 130 and 195 , including ^ { 182 } Hf , but very little ^ { 129 } I .
In order to match the solar r -process abundance pattern and to satisfy the ^ { 129 } I and ^ { 182 } Hf constraints , the events in case L , which would make the r -process nuclei near A \sim 130 and the bulk of those between A \sim 130 and 195 , must occur \sim 10 times less frequently but eject \sim 10 –20 times more r -process material in each event .

Assuming that all of the supernovae producing r -process nuclei represent a similar overall process , we speculate that the usual neutron star remnants , and hence prolonged ejection of r -process material , are associated with the events in case L. We further speculate that the more frequently occurring events in case H have ejection of other r -process material terminated by black hole formation during the neutrino cooling phase of the protoneutron star .
This suggests that there is now an inventory of \sim 5 \times 10 ^ { 8 } black holes with masses \sim 1 M _ { \odot } and \sim 5 \times 10 ^ { 7 } neutron stars resulting from supernovae in the Galaxy .
This r -process model would have little effect on the estimates of the supernova contributions to the non- r -process nuclei .