Can a star with a black hole core be stable?

[magic9mushroo]

If a small black hole were to fall into a star or brown dwarf, presumably it would initiate accretion and fusion in a shell around it.

Can such an object be stable over any decent timescale, or would it undergo variability/significant mass loss/supernova?

[Vagn]

There's a hypothesised object called a quasistar (http://en.wikipedia.org/wiki/Quasistar), which is thought to be a large black hole surrounded by a cloud of gas, which sounds somewhat similar to what you are looking for. They are a candidate for supermassive black hole formations. I suspect an object identical to the one you describe would be unstable, and probably wouldn't last very long, before all the gas was accreted.

[Nabeshin]

Since the gas composing a star is not in orbit around the center of mass, but rather held there by pressure, once you remove that pressure at the middle of the star there is no method to halt all the gas from simply falling into the gravitational potential. So, unless there was some method of acquiring enough angular momentum in the outer gas shells to actually achieve an orbit, such an object would inevitably collapse into a simple black hole.

[magic9mushroo]

So you're saying that the key distinction between this and a Thorne-Zytkow object is the lack of a solid surface on a black hole?

[russ_watters]

What? None of what is being discussed involves a solid surface on anything.

[Nabeshin]

What? None of what is being discussed involves a solid surface on anything.

Well, I do see where he got that from what I said. In essence, a solid surface corresponds to some kind of pressure holding the object together and preventing gravitational collapse (the word solid is used loosely). I don't like the wording there though, the real key thing is there is no opposing pressure to balance gravitation.

[Nik_2213]

Uh, given rotation, I must wonder if the 'star' would collapse into an accretion disk...