Stellar sources of the short-lived radionuclides in the earlysolar system

摘要

We discuss the possible stellar sources of short-lived radionuclides (SLRs) known to have been present in the early solar system (~26m,~36C1, ~41ca, ~53Mn, ~60Fe, ~107pd,~1291, ~152Hf, ~244pus ).SLRs produced primarily by irradiation (~7Be, ~10Be) are notdiscussed in this paper. We evaluate the role of the galactic background in explaining the inventory of SLRs in the early solarsystem. We review the nucleosynthetic processes that produce the different SLRs and place the processes in the context ofstellar evolution of stars from 1 to 120 M_Θ.The ejection of newly synthesized SLRs from these stars is also discussed. Wethen examine the extent to which each stellar source can, by itself, explain the relative abundances of the different SLRs inthe early solar system, and the probability that each source would have been in the right place at the right time to providethe SLRs. We conclude that intermediate-mass AGB stars and massive stars in the range from —20 to —60 M are the mostplausible sources. Low-mass AGB stars fail to produce enough ~60Fe. Core-collapse Type II supernovae from stars with initialmasses of <20 M_Θ produce too much ~60Feand ~53Mn. Sources such as novae, Type Ia supernovae, and core-collapse super-novae of 0—Ne—Mg white dwarfs do not appear to provide the SLRs in the correct proportions. However, intermediate-massAGB stars cannot provide ~53Mnor the r-process elements, so if an AGB star provided the ~41Ca, ~36C1, ~26A1, 60Fe, and ~107Pd,and if a late stellar source is required for ~53Mnand the r-process elements, then two types of sources would be required. Aseparate discussion of the production of r-process elements highlights the difficulties in modeling their production. Thereappear to be two sources of r-process elements, one that produces the heavy r-process elements, including the actinides,and one that produces the elements from N tope and the elements —110 < A < —130. These can be assigned to SNII explo-sions of stars of :11 M_Θ and stars of 12-25 M_Θ,respectively. More-massive stars, which leave black holes as supernova rem-nants, apparently do not produce r-process elements.