Origin of the p -process radionuclides ⁹² Nb and ¹⁴⁶ Sm in the early solar system and inferences on the birth of the Sun

Abstract

The abundances of 92 Nb and 146 Sm in the early solar system are determined from meteoritic analysis, and their stellar production is attributed to the p process. We investigate if their origin from thermonuclear supernovae deriving from the explosion of white dwarfs with mass above the Chandrasekhar limit is in agreement with the abundance of 53 Mn, another radionuclide present in the early solar system and produced in the same events. Mo ratio in the early solar system to be at least 50% lower than the current nominal value, which is outside its present error bars. A different solution is to invoke another production site for 92 Nb, which we find in the α-rich freezeout during core-collapse supernovae from massive stars. Whichever scenario we consider, we find that a relatively long time interval of at least ∼10 My must have elapsed from when the star-forming region where the Sun was born was isolated from the interstellar medium and the birth of the Sun. This is in agreement with results obtained from radionuclides heavier than iron produced by neutron captures and lends further support to the idea that the Sun was born in a massive star-forming region together with many thousands of stellar siblings.short-lived radionuclides | solar system formation | supernovae

Explosive Nucleosynthesis Study Using Laser Driven γ-ray Pulses

“…Because the neutrino-nucleus interaction is extremely weak, the neutrino process alone can play a significant role in the syntheses of isotopes which are bypassed by other major processes such as r, s, and γ processes. The neutrino process in supernova explosions was proposed as the astrophysical origin of rare isotopes such as 7 Li, 11 B, 19 F, 138 La, and 180 Ta [16,17]. Among elements heavier than iron, only two isotopes of 138 La and 180 Ta were known as the ν isotopes.…”

“…Hayakawa et al [18] presented that the initial abundance of 92 Nb could be explained by a scenario wherein a supernova explosion happened at the time 10 6 -3 × 10 7 y. before the solar system's formation. Note that the origin of 92 Nb is still a subject of study [19,20]. In this way, the study of nucleosyntheses can contribute to the understanding of the history before the solar system's formation as well as the origin of materials.…”

“…The half-lives of excited states with excitation energies of 0−500 keV are typically in the range from picosecond to nanosecond. Figure 7 shows partial level schemes of the two ν isotopes, 19 F and 138 La, and two p nuclei, 164 Er and 190 Pt. The half-lives of the first and second excited states in 19 F are 581 ps and 89.3 ns, respectively.…”

“…Figure 7 shows partial level schemes of the two ν isotopes, 19 F and 138 La, and two p nuclei, 164 Er and 190 Pt. The half-lives of the first and second excited states in 19 F are 581 ps and 89.3 ns, respectively. 138 La is an important ν-isotope, but the half-lives of its excited states are not known.…”

Nucleosynthesis ofNb92and the relevance of the low-lying isomer at 135.5 keV

“…For this purpose the production of these unstable nuclei is compared to the abundance in the early solar system which can be derived from meteoritic data (e.g., [6][7][8][9][10][11][12] Nb in a proton-rich p-process environment. As astrophysical sites for the p-process, supernova (SN) explosions of corecollapse type (SN type-II) or thermonuclear explosions of white dwarfs (SN type Ia) have been suggested (e.g., [13][14][15][16]).…”