Question About Collapsing Supernova

[GIASAL]

The inner part of the core, about 0.4 to 0.6 M⊙, is in sonic contact and collapses homologously, while the outer core collapses supersonically.

Hi
Could you explain the meaning of this sentence to me as simply as possible?

 

[renormalize]

The inner part of the core, about 0.4 to 0.6 M⊙, is in sonic contact and collapses homologously, while the outer core collapses supersonically.

Please cite the specific source of this statement.

 

[GIASAL]

https://royalsocietypublishing.org/...e-mechanism-s-of-core-collapse-supernovaeCCSN
In the section "Modern view of stellar core collapse"

 

[Matterwave]

The inner part of the core, about 0.4 to 0.6 M⊙, is in sonic contact and collapses homologously, while the outer core collapses supersonically.

There are 2 "sections" of the core, the inner and outer cores. The inner core, which has a mass around 0.4 to 0.6 solar masses (meaning it has about the same mass as 40% to 60% of our Sun's mass), collapses slower than the speed of sound of the material ("sonic contact") and thereby "homologously" (in pressure, density, temperature) throughout (which I will explain below). The outer core collapses faster than the speed of sound of the material.

What does "homologous" mean here? Homologous collapse means the collapse velocity is proportional to the radius ($v\propto r$) so that the shape (not the values, but the shape!) of the pressure/density/temperature profiles $P(r),\,\rho(r),\,T(r)$ doesn't change during collapse -- they just shrink radially. There's no over steepening or under steepening. The profiles just steepen in proportion to the shrinking.

We can discuss "homologous collapse" more if there are follow up questions. That's the main technical point in the sentence.