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Technetium-98 nuclear cosmochronometer synthesized by supernova neutrinos

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September 19, 2018

A team of researchers has theoretically predicted that an unstable isotope Technetium-98 (98Tc) could be synthesized by neutrinos emitted from supernova explosions.

Figure 1. Element production by neutrinos emitted on supernova explosion

Figure 1. Element production by neutrinos emitted on supernova explosion

A large number of neutrinos are emitted from the proto-neutron star formed during an early phase of a core-collapse supernova. When these neutrinos pass through the outer layers, they partially deposit their energy in the outer layers, leading its supernova explosion. In the outer layers, some nuclides such as Tantalum-180 are newly synthesized by the neutrino-nucleus interaction. There are six neutrino species, electron neutrino, muon neutrino, tau neutrino, and their anti-neutrinos.

Previous studies have shown that the neutrino-isotopes are predominantly produced by five neutrino species except the electron anti-neutrino. If there was a neutrino-isotope synthesized predominantly by the electron anti-neutrino, one could estimate the temperature of the six neutrino species, which are important for understanding the supernova explosion mechanism.

At the present study, first, it was found the possibility that 98Tc may be synthesized by the neutrino process.

Next, the expected 98Tc abundance was calculated using a supernova explosion model with the neutrino-nucleus interactions involved.

As a result, it was found that 98Tc neutrino-process nucleosynthesis is the large contribution (~20%) from charged current reactions with electron anti-neutrinos. It was shown that if the initial abundances of 98Tc were to be precisely measured, the 98Tc nuclear cosmochronometer could be used to evaluate the initial abundance of 98Tc and the duration time from the last core-collapse supernova to the formation of the solar system.

Figure 2. Substances formed in supernova are drawn together into the proto-solar system

Figure 2. Substances formed in supernova are drawn together into the proto-solar system

The present result is also important for the average temperatures of the six neutrinos and astronomical observation of the electron anti-neutrino.

This work will be published in Physical Review Letters.


Authors : Takehito Hayakawa1,2,*, Haemin Ko3, Myung-Ki Cheoun3, Motohiko Kusakabe4, Toshitaka Kajino2,4,5, Mark D. Usang6, Satoshi Chiba6, Ko Nakamura7, Alexey Tolstov8, Ken'ichi Nomoto8, Masa-aki Hashimoto9, Masaomi Ono10, Toshihiko Kawano11, Grant J. Mathews12
Title of original paper : Short-Lived Radioisotope 98Tc Synthesized by the Supernova Neutrino Process
Journal : Physical Review Letters
DOI : 10.1103/PhysRevLett.121.102701 別窓
Affiliations :

1National Institutes for Quantum and Radiological Science and Technology, Japan

2National Astronomical Observatory of Japan, Japan

3Soongsil University, Korea

4Beihang University, China

5The University of Tokyo, Japan

6Tokyo Institute of Technology, Japan

7Fukuoka University, Japan

8Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo, Japan

9Department of Physics, Kyushu University

10RIKEN, Japan

11Theoretical Division, Los Alamos National Laboratory, USA

12University of Notre Dame, USA


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