Neutron Star Mergers Might Not Be the Only Source of r -process Elements in the Milky Way
Name
Côté_2019_ApJ_875_106.pdf
Description
Published version
Size
4.64 MB
Format
Adobe PDF
Checksum (MD5)
a63ee2808a52a125178f5474484e5afd
Author(s)
Frebel, Anna L.
Date Issued
April 2019
Journal
Astrophysical Journal
Publisher
American Astronomical Society
Citation
Côté, Benoit et al. “Neutron Star Mergers Might Not Be the Only Source of r -process Elements in the Milky Way.” Astrophysical Journal, 875, 2 (April 2019): 106 © 2019 The Author(s)
Version
Final published version
Abstract
We review the observational evidence that probes the properties of r-process sites, and address them using galactic chemical evolution simulations, binary population synthesis models, and nucleosynthesis calculations. Our motivation is to define which astrophysical sites have significantly contributed to the total mass of r-process elements present in our Galaxy. We found discrepancies with the neutron star (NS-NS) merger scenario. When we assume that they are the only site, the decreasing trend of [Eu/Fe] at [Fe/H] > -1 in the disk of the Milky Way cannot be reproduced while accounting for the delay-time distribution (DTD) of coalescence times (∝t -1) derived from short gamma-ray bursts (GRBs) and population synthesis models. Steeper DTD functions (∝t -1.5) or power laws combined with a strong burst of mergers before the onset of supernovae (SNe) Ia can reproduce the [Eu/Fe] trend, but this scenario is inconsistent with the similar fraction of short GRBs and SNe Ia occurring in early-type galaxies, and it reduces the probability of detecting GW170817 in an early-type galaxy. One solution is to assume an additional production site of Eu that would be active in the early universe, but would fade away with increasing metallicity. If this is correct, this additional site could be responsible for roughly 50% of the Eu production in the early universe before the onset of SNe Ia. Rare classes of supernovae could be this additional r-process source, but hydrodynamic simulations still need to ensure the conditions for a robust r-process pattern.
MIT Department
Massachusetts Institute of Technology. Department of Physics
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DOI of Published Version
https://doi.org/10.3847/1538-4357/AB10DB
