Short-Lived Radioisotope Tc98 Synthesized by the Supernova Neutrino Process

Abstract

The isotope ^{98}Tc decays to ^{98}Ru with a half-life of 4.2×10^{6} yr and could have been present in the early Solar System. In this Letter, we report on the first calculations of the production of ^{98}Tc by neutrino-induced reactions in core-collapse supernovae (the ν process). Our predicted ^{98}Tc abundance at the time of solar system formation is not much lower than the current measured upper limit raising the possibility for its detection in the not too distant future. We show that, if the initial abundance were to be precisely measured, the ^{98}Tc nuclear cosmochronometer could be used to evaluate a much more precise value of the duration time from the last core-collapse supernova to the formation of the solar system. Moreover, a unique and novel feature of the ^{98}Tc ν-process nucleosynthesis is the large contribution (∼20%) from charged current reactions with electron antineutrinos. This means that ^{98}Tc becomes a unique new ν-process probe of the temperature of the electron antineutrinos.

Effects of Shock Propagation on Neutrino Oscillation and $\nu $-induced Nucleosynthesis in Supernova

“…In the region around 3.3 M , the 2 nd ν-flavor oscillation occurs and the electron neutrino returns to its initial flux before the third resonance near to 4.7 M . The interesting point in this HD model is that the first resonance resembles the MSW region estimated by the other HD model used in our previous calculation [7]. These resonance effects are reflected in results of the ν process in Fig.…”

“…The reaction network for the explosive nucleosynthesis calculation is the same as that used in Ref. [7]. In this study, the most effective physical quantity is the density profile during the SN explosion given by adopted HD models, for which we use the public blcode with the initial density profile in Ref.…”

“…Understanding of ν oscillation in matter is not just limited to the purpose of solving the solar-ν problem, but also unavoidable for explaining the ν-induced nucleosynthesis [6,7] as well as the ν detection on Earth [8]. In this study, we focus on the ν oscillation in matter owing to the SH propagation during SN explosion.…”

Progress in nuclear astrophysics of east and southeast Asia

“…It was found for the first time that remarkable amount of radioactive isotope 98 Tc is produced via charged-current reactions byν e although the other nuclei are produced mainly by the ν e -nucleus interactions. Thus, 98 Tc is characterized as a special probe of SNν e spectrum [285]. Extensive calculations showed that another short-lived radioactive isotope 92 Nb and stable ones 138 La and 180 Ta also are produced in the ν-process.…”

Effects of the Metallicity on Li and B Production in Supernova Neutrino Process

“…This process, as well as the 3 He(α,γ) 7 Be reaction [3,4] in asymptotic giant branch stars [5], red giants [6], and novae [7], and the production of LiBeB isotopes in cosmic ray nucleosynthesis via the spallation of CNO and α + α fusion [8,9], is, therefore, important in Galactic chemical evolution of light elements. SN explosions are energized by neutrinos emitted from the proto-neutron star (NS), and neutrino reactions with nuclei in the stellar interior produces a number of rare stable nuclei including 7 Li, 11 B, 138 La, and 180 Ta [1,2,10] as well as short-lived nuclei 92 Nb and 98 Tc [11][12][13]. Among them, production of the light elements Li and B occurs in the C-and He-rich layers inside of which neutrino flavor mixing can effectively occur due to the influence of the stellar electrons.…”