Graduate School of Science, Tohoku University

Institute for Fusion Science

Graduate School of Science, The University of Tokyo

National Astronomical Observatory of Japan

Abstract of Presentation

The origin of gold, platinum, and rare earths in the universe has been a long-standing unsolved problem in astronomy and astrophysics. Neutron star mergers have been considered the most likely source, but it has not been clear what elements were actually synthesized in such events.

In order to decipher the light spectrum from neutron star mergers, a research group led by Nanae Tsuchimoto, a graduate student (JSPS Research Fellow, Academic Support Staff) at Graduate School of Science, Tohoku University, has comprehensively studied the properties of all heavy elements and ^performed detailed numerical As a result of the simulation, it was revealed that some rare earths, lanthanum and cerium, can explain the features of the infrared spectra actually observed in neutron star mergers. This is the first direct evidence that individual rare earths were created in neutron star mergers, and will greatly advance our understanding of the origin of elements in the universe.

The results of this research were published in the electronic edition of The Astrophysical Journal on October 26, 2022.

Figure: Spectra of "kilonova" observed by GW170817 (gray ) and obtained in this study (blue ) . The numbers on the left indicate the number of days since the neutron star merger occurred. The dashed lines indicate absorption line features, and the same colors indicate the names of the elements that make up those features. The spectra are shifted along the vertical axis for easy viewing. The observed spectra around 1400 nm and 1800-1900 nm are affected by the Earth's atmosphere. ©️Domoto et al.

Associate Professor Kenta Furusaka of the Research Center for the Early Universe is participating in this research.

For more information, please visit the website of Graduate School of Science, Tohoku University.