Neutron star collisions as a heavy element source

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Discussion Overview

The discussion centers on the role of neutron star collisions in the production of heavy elements, particularly in light of recent observations and analyses. Participants explore the mechanisms behind element distribution in the galaxy, the speeds at which these elements are ejected, and the comparative contributions of neutron star mergers and supernovae to the observed elemental abundances.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants suggest that neutron star-neutron star (NS-NS) mergers are a significant source of heavy elements, citing a recent paper that aligns with observed abundances on Earth.
  • Others question the rarity of NS-NS mergers, arguing that supernovae are likely the primary source of heavy elements, supported by historical data and literature.
  • Participants discuss the rapid neutron-capture process (r-process) and its importance in creating heavy elements, with some expressing curiosity about the mechanisms that distribute these elements throughout the galaxy.
  • There are inquiries about the speeds at which heavy elements are ejected during neutron star collisions, with some estimates provided from the referenced paper.
  • Some participants express skepticism about the ability of NS-NS mergers to account for all heavy elements, suggesting that models indicate supernovae alone do not produce enough neutron-rich elements.
  • Discussions include the complexities of nucleosynthesis during supernova events, particularly regarding core collapse and the conditions necessary for heavy element formation.
  • There are references to specific models and papers that propose alternative explanations for the observed elemental abundances, including homologous core collapse scenarios.
  • Some participants challenge the claims made about the rarity of NS-NS mergers, requesting calculations and references to support these assertions.

Areas of Agreement / Disagreement

Participants express a range of views, with significant disagreement on the contributions of neutron star collisions versus supernovae in producing heavy elements. Some participants assert that NS-NS mergers are too rare to account for the observed abundances, while others argue that recent studies suggest otherwise. The discussion remains unresolved, with multiple competing perspectives present.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the rates of NS-NS mergers and their yields, as well as the dependence on specific models of nucleosynthesis. The uncertainty in the rates of these events and the complexities of supernova mechanisms are acknowledged but not fully resolved.

  • #31
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  • #32
This is why we keep coming back. I never seem quite able to manage leaving here dumber than I was upon arrival.
 
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  • #33
I think there's a lot of that going on. ;-)
 
  • #34
JMz said:
Yeah. But X-rays are another way to find NSs, which might give a handle on the ratio: imprecise, but even factor-of-2 accuracy would be plenty at this point.

BTW:

Presumably neutrons would not participate in this flow, as they are electrically neutral. At the NS surfaces, they will decay into protons & electrons, which can.
Neutrons don't have an electric charge, it's true, but they do have a magnetic moment on the same order of magnitude as the proton and so would be affected significantly by the neutron stars' powerful magnetic fields. In fact, it was the neutron's magnetic moment that gave the first hint that the neutron had some sort of internal structure.
But let me clarify another point - there's no reason to think that as the neutron stars get closer that their magnetic fields would force them to flip upside down. The magnetic force is very short range, and even though very powerful still overshadowed by gravitational attraction, although interaction of their magnetic fields might alter the neutron stars dynamics appreciably.
One more thing, from this thread it appears that you seem to think that there are pulsars and then there are neutron stars with no appreciable magnetic fields. All neutron stars have magnetic fields and are pulsars. The only reason we can't observe them all is that not all of them are aligned with our line of sight.
 
  • #35
alantheastronomer said:
Neutrons don't have an electric charge, it's true, but they do have a magnetic moment on the same order of magnitude as the proton and so would be affected significantly by the neutron stars' powerful magnetic fields. In fact, it was the neutron's magnetic moment that gave the first hint that the neutron had some sort of internal structure.
True. I took the previous post to be focused on the currents, only.
...One more thing, from this thread it appears that you seem to think that there are pulsars and then there are neutron stars with no appreciable magnetic fields. All neutron stars have magnetic fields and are pulsars. The only reason we can't observe them all is that not all of them are aligned with our line of sight.
[If you are still addressing my post at this point, rather than @Chronos's, to which I was replying:]
Agreed, though my comment was only about X-rays as an alternative mode of discovery: The pulsar behavior might be unobservable because of alignment or otherwise, whereas looking for X-rays would also be unsuccessful for some (perhaps most) NSs but would be subject to a different set of selection effects than pulsar behavior.
 

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