We explore the effects of nuclear masses on the temperature and neutron density conditions required for r -process nucleosynthesis using four nuclear mass models augmented by the latest atomic mass evaluation .
For each model we derive the conditions for producing the observed abundance peaks at mass numbers A \sim 80 , 130 , and 195 under the waiting-point approximation and further determine the sets of conditions that can best reproduce the r -process abundance patterns ( r -patterns ) inferred for the solar system and observed in metal-poor stars of the Milky Way halo .
In broad agreement with previous studies , we find that ( 1 ) the conditions for producing abundance peaks at A \sim 80 and 195 tend to be very different , which suggests that , at least for some nuclear mass models , these two peaks are not produced simultaneously ; ( 2 ) the typical conditions required by the critical waiting-point ( CWP ) nuclei with the N = 126 closed neutron shell overlap significantly with those required by the N = 82 CWP nuclei , which enables coproduction of abundance peaks at A \sim 130 and 195 in accordance with observations of many metal-poor stars ; and ( 3 ) the typical conditions required by the N = 82 CWP nuclei can reproduce the r -pattern observed in the metal-poor star HD 122563 , which differs greatly from the solar r -pattern .
We also examine how nuclear mass uncertainties affect the conditions required for the r -process and identify some key nuclei including ^ { 76 } Ni to ^ { 78 } Ni , ^ { 82 } Zn , ^ { 131 } Cd , and ^ { 132 } Cd for precise mass measurements at rare-isotope beam facilities .