Neutron Star Mergers as the Main Source of R-process: Natal Kicks And Inside-Out Evolution to The Rescue. (arXiv:2007.04442v1 [astro-ph.GA])

Neutron Star Mergers as the Main Source of R-process: Natal Kicks And Inside-Out Evolution to The Rescue. (arXiv:2007.04442v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Banerjee_P/0/1/0/all/0/1">Projjwal Banerjee</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wu_M/0/1/0/all/0/1">Meng-Ru Wu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yuan_Z/0/1/0/all/0/1">Zhen Yuan</a>

Binary neutron star mergers (BNSMs) is currently the most promising source of
textsl{r}-process thanks to the detection of GW170817. The estimated occurring
frequency and the amount of mass ejected per merger indicate that BNSMs by
itself can account for all the textsl{r}-process enrichment in the Galaxy.
However, the decreasing trend of [Eu/Fe] vs [Fe/H] of disk stars for
[Fe/H]$gtrsim -1$ in the solar neighborhood is inconsistent with the flat
trend expected from BNSMs with a standard delay time distribution (DTD)
$propto t^{-1}$. This has led to the suggestion that either additional sources
or modification to the DTD of BNSMs is required to match the observations. We
investigate the effects of natal kicks received during the birth of neutron
star binaries on the chemical evolution of textsl{r}-process element Eu in the
Milky Way by combining the results from the galactic dynamics code
textsc{galpy} with a one-zone Galactic chemical evolution model
textsc{omega}. We show that when key inputs from simulations of the inside-out
disk evolution are combined with natal kicks, BNSMs can naturally reproduce the
observed decreasing trend of [Eu/Fe] with [Fe/H] in the solar neighborhood
without the need for modification to the DTD or additional textsl{r}-process
sources.

Binary neutron star mergers (BNSMs) is currently the most promising source of
textsl{r}-process thanks to the detection of GW170817. The estimated occurring
frequency and the amount of mass ejected per merger indicate that BNSMs by
itself can account for all the textsl{r}-process enrichment in the Galaxy.
However, the decreasing trend of [Eu/Fe] vs [Fe/H] of disk stars for
[Fe/H]$gtrsim -1$ in the solar neighborhood is inconsistent with the flat
trend expected from BNSMs with a standard delay time distribution (DTD)
$propto t^{-1}$. This has led to the suggestion that either additional sources
or modification to the DTD of BNSMs is required to match the observations. We
investigate the effects of natal kicks received during the birth of neutron
star binaries on the chemical evolution of textsl{r}-process element Eu in the
Milky Way by combining the results from the galactic dynamics code
textsc{galpy} with a one-zone Galactic chemical evolution model
textsc{omega}. We show that when key inputs from simulations of the inside-out
disk evolution are combined with natal kicks, BNSMs can naturally reproduce the
observed decreasing trend of [Eu/Fe] with [Fe/H] in the solar neighborhood
without the need for modification to the DTD or additional textsl{r}-process
sources.

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