GW170817–the first observed neutron star merger and its kilonova: implications for the astrophysical site of the r-process. (arXiv:1901.09044v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Siegel_D/0/1/0/all/0/1">Daniel M. Siegel</a>
The first neutron star (NS) merger observed by advanced LIGO and Virgo,
GW170817, and its fireworks of electromagnetic counterparts across the entire
electromagnetic spectrum marked the beginning of multi-messenger astronomy and
astrophysics with gravitational waves. The ultraviolet, optical, and
near-infrared emission was consistent with being powered by the radioactive
decay of nuclei synthesized in the merger ejecta by the rapid neutron capture
process (r-process). Starting from an outline of the inferred properties of
this ‘kilonova’ emission, I discuss possible astrophysical sites for r-process
nucleosynthesis in NS mergers, arguing that the heaviest r-process elements
synthesized in this event most likely originated in outflows from a post-merger
accretion disk. I compare the inferred properties of r-process element
production in GW170817 to current observational constraints on galactic heavy
r-process nucleosynthesis and discuss challenges merger-only models face in
explaining the r-process content of our galaxy. Based on the observational
properties of GW170817 and recent theoretical progress on r-process
nucleosynthesis in collapsars, I then show how GW170817 points to collapsars as
the dominant source of r-process enrichment in the Milky Way, which arguably
better satisfy existing constraints and overcome the problems NS mergers face.
Finally, I comment on the universality of the r-process and on how variations
in light r-process elements can be obtained both in NS mergers and collapsars.
The first neutron star (NS) merger observed by advanced LIGO and Virgo,
GW170817, and its fireworks of electromagnetic counterparts across the entire
electromagnetic spectrum marked the beginning of multi-messenger astronomy and
astrophysics with gravitational waves. The ultraviolet, optical, and
near-infrared emission was consistent with being powered by the radioactive
decay of nuclei synthesized in the merger ejecta by the rapid neutron capture
process (r-process). Starting from an outline of the inferred properties of
this ‘kilonova’ emission, I discuss possible astrophysical sites for r-process
nucleosynthesis in NS mergers, arguing that the heaviest r-process elements
synthesized in this event most likely originated in outflows from a post-merger
accretion disk. I compare the inferred properties of r-process element
production in GW170817 to current observational constraints on galactic heavy
r-process nucleosynthesis and discuss challenges merger-only models face in
explaining the r-process content of our galaxy. Based on the observational
properties of GW170817 and recent theoretical progress on r-process
nucleosynthesis in collapsars, I then show how GW170817 points to collapsars as
the dominant source of r-process enrichment in the Milky Way, which arguably
better satisfy existing constraints and overcome the problems NS mergers face.
Finally, I comment on the universality of the r-process and on how variations
in light r-process elements can be obtained both in NS mergers and collapsars.
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