60Fe and 244Pu deposited on Earth constrain the r-process yields of recent nearby supernovae

A Wallner; M B Froehlich; M A C Hotchkis; N Kinoshita; M Paul; M Martschini; S Pavetich; S G Tims; N Kivel; D Schumann; M Honda; H Matsuzaki; T Yamagata

doi:10.1126/science.aax3972

⁶⁰Fe and ²⁴⁴Pu deposited on Earth constrain the r-process yields of recent nearby supernovae

Science. 2021 May 14;372(6543):742-745. doi: 10.1126/science.aax3972.

Authors

A Wallner^{1

2}, M B Froehlich³, M A C Hotchkis⁴, N Kinoshita⁵, M Paul⁶, M Martschini³, S Pavetich³, S G Tims³, N Kivel⁷, D Schumann⁷, M Honda⁸, H Matsuzaki⁹, T Yamagata⁹

Affiliations

¹ Department of Nuclear Physics, Research School of Physics, Australian National University, Canberra, ACT 2601, Australia. [email protected] [email protected].
² Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, 01328 Dresden, Germany.
³ Department of Nuclear Physics, Research School of Physics, Australian National University, Canberra, ACT 2601, Australia.
⁴ Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia.
⁵ Institute of Technology, Shimizu Corporation, Tokyo 135-8530, Japan.
⁶ Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
⁷ Laboratory of Radiochemistry, Department for Nuclear Energy and Safety, Paul Scherrer Institute, 5232 Villigen, Switzerland.
⁸ Graduate School of Pure and Applied Sciences, University of Tsukuba, Ibaraki 305-8577, Japan.
⁹ Micro Analysis Laboratory, Tandem Accelerator, The University Museum, The University of Tokyo, Tokyo 113-0032, Japan.

PMID: 33986180
DOI: 10.1126/science.aax3972

Abstract

Half of the chemical elements heavier than iron are produced by the rapid neutron capture process (r-process). The sites and yields of this process are disputed, with candidates including some types of supernovae (SNe) and mergers of neutron stars. We search for two isotopic signatures in a sample of Pacific Ocean crust-iron-60 (⁶⁰Fe) (half-life, 2.6 million years), which is predominantly produced in massive stars and ejected in supernova explosions, and plutonium-244 (²⁴⁴Pu) (half-life, 80.6 million years), which is produced solely in r-process events. We detect two distinct influxes of ⁶⁰Fe to Earth in the last 10 million years and accompanying lower quantities of ²⁴⁴Pu. The ²⁴⁴Pu/⁶⁰Fe influx ratios are similar for both events. The ²⁴⁴Pu influx is lower than expected if SNe dominate r-process nucleosynthesis, which implies some contribution from other sources.

Publication types

Research Support, Non-U.S. Gov't