When the two neutron stars merged in the latest event, large amounts of gamma rays were emitted. Given that their deorbitting is a result of gravitational wave production, where does the energy for the gamma rays come from?

The only sources I can think of are the rotational kinetic energies of the merging stars or the potential energy released by the final collapse into a single spherical mass.


Not Nuclear fusion;
There is also a huge amount of nuclear fusion that creates heavy elements from all the iron there is in neutron star: they in fact are not only made of neutrons. But as said in comment, building of heavier elements rather consumes energy than it generates some.

Not sure scientists has a clear agreement on how this works.

Gravitational collapse

For example I found this (rather old) abstract which states it could be a result of gravitational collapse, without singularity (since here the result of the merger might not be a black-hole, or the lightest ever: around 2.7 solar masses!)

theoretical developments (string theory, quantum gravity, critical collapse), which suggest that complete gravitational collapse can occur without singularities or event horizons

Thermonuclear event again: fission

From Space.com, they say Kilonova energy could be explained by rapid atomic decay of heavy elements

The mergers of dense cosmic bodies that are thought to cause short gamma-ray bursts can also blast out neutron-rich gas that rapidly generates heavy elements such as gold and platinum, scientists say. These "r-process" elements can undergo radioactive decay and release an enormous amount of energy — 1,000 times or so that given off by stellar explosions such as novas. These powerful events are thus known as "kilonovas"

| improve this answer | |
  • 2
    $\begingroup$ My understanding is that fusion of elements heavier than iron absorbs energy rather than emitting it? I would think there would be another mechanism for turning the potential and kinetic energy of the colliding neutron stars into gamma ray emission (really, really hot accretion disk?) $\endgroup$ – antlersoft Oct 17 '17 at 15:10
  • $\begingroup$ I read the article on gravitational collapse you mentioned. It would have been nice to see a mathematical treatment that justifies the posited "red hole" the author describes or at least a citation to such. Without that, it's difficult to see that as a likely scenario. I do like the idea that some of the matter from one or both stars is ejected as that address with the spectral analysis that shows heavier elements in the mix. $\endgroup$ – C Teegarden Oct 18 '17 at 21:49

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.