TY - JOUR
T1 - On Neutron Star Mergers as the Source of r-process-enhanced Metal-poor Stars in the Milky Way
AU - Safarzadeh, Mohammadtaher
AU - Sarmento, Richard
AU - Scannapieco, Evan
N1 - Publisher Copyright:
© 2019. The American Astronomical Society. All rights reserved.
PY - 2019/5/1
Y1 - 2019/5/1
N2 - We model the history of Galactic r-process enrichment using high-redshift, high-resolution zoom cosmological simulations of a Milky Way-type halo. We assume that all r-process sources are neutron star mergers (NSMs) with a power-law delay time distribution. We model the time to mix pollutants at subgrid scales, which allows us to better compute the properties of metal-poor (MP) and carbon-enhanced metal-poor (CEMP) stars, along with statistics of their r-process-enhanced subclasses. Our simulations underpredict the cumulative ratios of r-process-enhanced MP and CEMP stars (MP-r, CEMP-r) over MP and CEMP stars by about one order of magnitude, even when the minimum coalescence time of the double neutron stars (DNSs), t min, is set to 1 Myr. No r-process-enhanced stars form if t min = 100 Myr. Our results show that even when we adopt the r-process yield estimates observed in GW170817, NSMs by themselves can only explain the observed frequency of r-process-enhanced stars if the birth rate of DNSs per unit mass of stars is boosted to .
AB - We model the history of Galactic r-process enrichment using high-redshift, high-resolution zoom cosmological simulations of a Milky Way-type halo. We assume that all r-process sources are neutron star mergers (NSMs) with a power-law delay time distribution. We model the time to mix pollutants at subgrid scales, which allows us to better compute the properties of metal-poor (MP) and carbon-enhanced metal-poor (CEMP) stars, along with statistics of their r-process-enhanced subclasses. Our simulations underpredict the cumulative ratios of r-process-enhanced MP and CEMP stars (MP-r, CEMP-r) over MP and CEMP stars by about one order of magnitude, even when the minimum coalescence time of the double neutron stars (DNSs), t min, is set to 1 Myr. No r-process-enhanced stars form if t min = 100 Myr. Our results show that even when we adopt the r-process yield estimates observed in GW170817, NSMs by themselves can only explain the observed frequency of r-process-enhanced stars if the birth rate of DNSs per unit mass of stars is boosted to .
KW - Galaxy: abundances
KW - stars: neutron
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U2 - 10.3847/1538-4357/ab1341
DO - 10.3847/1538-4357/ab1341
M3 - Article
AN - SCOPUS:85067181096
SN - 0004-637X
VL - 876
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 28
ER -