How does a collapsing core become a black hole?

[durand]

Hi,

I'm trying to understand how exactly a black hole fits into the evolution of red supergiants, especially in terms of a timeline. I understand that when the core of the star collapses, it reaches a point where the neutron pressure overcomes it's gravitational force and this deceleration (and bounce back) of matter causes the shock wave that creates a type II supernova.
However, does this only apply to cores less than the chandrasekhar limit which form neutron stars or also to those above that limit which form black holes? I can't see how a supernova could be caused when there isn't enough neutron pressure to halt the core collapse and therefore cause the shock wave. So my question is basically, would there be a supernova when (just before) a black hole is created?

I'm pretty sure I'm missing something here but I can't seem to find what it is...

 

[mgb_phys]

You can still have an outgoing shock wave even if you don't form a neutron star surface.
The outer envelope of the star expands to form the supernova driven by the energy given off by the collapsing core - it doesn't really matter what the core ends up becoming.

 

[durand]

Oh, I read (on wikipedia and some books) that a shock wave causes the supernova, and that this shock wave is caused by the bounce back of matter. I guess you would get a lot of energy converted from gravitational potential as the core collapses?

 

[mgb_phys]

Yes it's not a shockwave bouncing off the neutron star surface, its an outgoing shockwave driven by the gravitational energy of the core collapse

 

[durand]

Yes it's not a shockwave bouncing off the neutron star surface, its an outgoing shockwave driven by the gravitational energy of the core collapse

Ok, that makes sense. Another simple question. Would a collapsing core become a neutron star first, or would it become a black hole in one fluid movement? Thanks for your help!