The supernova yields of r-process elements are obtained as a function of the mass of their progenitor stars from the abundance patterns of extremely metal-poor stars on the left-side [ Ba/Mg ] - [ Mg/H ] boundary with a procedure proposed by Tsujimoto and Shigeyama .
The ejected masses of r-process elements associated with stars of progenitor mass M _ { ms } \leq 18 M _ { \odot } are infertile sources and the SNe II with 20 M _ { \odot } \leq M _ { ms } \leq 40 M _ { \odot } are the dominant source of r-process nucleosynthesis in the Galaxy .
The ratio of these stars 20 M _ { \odot } \leq M _ { ms } \leq 40 M _ { \odot } with compared to the all massive stars is about \sim 18 % .
In this paper , we present a simple model that describes a star ’ s [ r/Fe ] in terms of the nucleosynthesis yields of r-process elements and the number of SN II explosions .
Combined the r-process yields obtained by our procedure with the scatter model of the Galactic halo , the observed abundance patterns of the metal-poor stars can be well reproduced .