A Very last pulse from a neutron star

[CGHW01]

TL;DR

Heating of neutron star matter during collapse leads to brief last pulse of light.

Considering that when you compress a gas, the gas will heat, then when a neutron star collapses to a black hole, I would expect the neutron matter to be heated to extreme values as the collapse proceeds. I would have thought this would lead to a last gasp pulse of em radiation before gravity would prevent any further emission. Perhaps the pulse would have a particular signature (pulse length and how the em radiation changes throughout the pulse) or maybe there would be no last pulse at all? I would imagine that during a neutron star merger, any such pulse would be dominated and hidden by all the other phenomena going on...

 

[DaveC426913]

Well, just like anything else just before it finally crosses the event horizon, it would be extremely red-shifted and getting more red-shifted with each passing nanosecond. In theory, you would have to wait virtually forever to be sure you've received the last ray of light, as each subsequent pulse gets longer and longer. If we're talking photons, you'll have to wait an arbitary length of time to be sure you've caught the very last time-dilated photon. You could wait billions of years.

It's a little like that adage: Q: How long does it take to perfectly tune a piano key? A: forever.

 

[Bosko]

Considering that when you compress a gas, the gas will heat, then when a neutron star collapses to a black hole..

Neutron star matter is quite different from gas.
Temperature is a measure of how much the molecules (atoms) of a material are jiggling ( Average kinetic energy )
To describe the collapse of a neutron star, one should rely more on quantum mechanics than on classical gas thermodynamics.