Did a Kilonova Set Off in Our Galactic Backyard 3.5 Myr ago?

Abstract

The recent detection of the live isotopes ${}^{60}\mathrm{Fe}$ and ${}^{244}\mathrm{Pu}$ in deep ocean sediments dating back to the past 3-4 Myr poses a serious challenge to the identification of their production site(s). While ${}^{60}\mathrm{Fe}$ is usually attributed to standard core-collapse supernovae, actinides are r-process nucleosynthesis yields, which are believed to be synthesized in rare events, such as special classes of supernovae or binary mergers involving at least one neutron star. Previous works concluded that a single binary neutron star merger cannot explain the observed isotopic ratio. In this work, we consider a set of numerical simulations of binary neutron star mergers producing long-lived massive remnants expelling both dynamical and spiral-wave wind ejecta. The latter, due to a stronger neutrino irradiation, also produce iron-group elements. Assuming that large-scale mixing is inefficient before the fading of the kilonova remnant and that the spiral-wave wind is sustained over a 100-200 ms timescale, the ejecta emitted at mid-high latitudes provide a ${}^{244}\mathrm{Pu}$ over ${}^{60}\mathrm{Fe}$ ratio compatible with observations. The merger could have happened 80-150 pc away from the Earth and between 3.5 and 4.5 Myr ago. We also compute expected isotopic ratios for eight other live radioactive nuclides showing that the proposed binary neutron star merger scenario is distinguishable from other scenarios proposed in the literature.

8 pages, 4 figures, accepted for publication in ApJL

References in corpus (22)

• Origin of the heavy elements in binary neutron-star mergers from a gravitational wave event
• Spectroscopic identification of r-process nucleosynthesis in a double neutron star merger
• A kilonova as the electromagnetic counterpart to a gravitational-wave source
• PSR J0952-0607: The Fastest and Heaviest Known Galactic Neutron Star
• Magnetorotationally driven Supernovae as the origin of early galaxy $r$-process elements?
• The dynamical mass ejection from binary neutron star mergers: Radiation-hydrodynamics study in general relativity
• AT2017gfo: an anisotropic and three-component kilonova counterpart of GW170817
• Star formation near the Sun is driven by expansion of the Local Bubble
• THC: a new high-order finite-difference high-resolution shock-capturing code for special-relativistic hydrodynamics
• SkyNet: A modular nuclear reaction network library
• General-Relativistic Large-Eddy Simulations of Binary Neutron Star Mergers
• A New Open-Source Nuclear Equation of State Framework based on the Liquid-Drop Model with Skyrme Interaction
• Binary neutron star merger simulations with neutrino transport and turbulent viscosity: impact of different schemes and grid resolution
• Astrophysical Shrapnel: Discriminating Among Near-Earth Stellar Explosion Sources of Live Radioactive Isotopes
• Second release of the CoRe database of binary neutron star merger waveforms
• Microscopic equation of state of hot nuclear matter for numerical relativity simulations
• Binary Neutron Star Merger Simulations with a Calibrated Turbulence Model
• Constraining Collapsar r-Process Models through Stellar Abundances
• Numerical studies on the link between radioisotopic signatures on Earth and the formation of the Local Bubble. II. Advanced modeling of interstellar 26Al, 53Mn, 60Fe, and 244Pu influxes as traces of past supernovae in the solar neighborhood
• Inhomogeneous enrichment of radioactive nuclei in the Galaxy: Deposition of live Mn-53, Fe-60, Hf-182, and Pu-244 into deep-sea archives. Surfing the wave?
• Proposed Lunar Measurements of $r$-Process Radioisotopes to Distinguish Origin of Deep-sea 244Pu
• Constraints on the frequency and mass content of r-process events derived from turbulent mixing in galactic disks

Cited by in corpus (5)

• Long-lived neutron-star remnants from asymmetric binary neutron star mergers: element formation, kilonova signals and gravitational waves
• Element formation in radiation-hydrodynamics simulations of kilonovae
• Open-source library for performance-portable neutrino reaction rates: Application to neutron star mergers
• Impact of in situ nuclear networks and atomic opacities on neutron star merger ejecta dynamics, nucleosynthesis, and kilonovae
• Exploring Composition Mixing in Kilonova Ejecta with Ray-by-ray Simulations