Colliding black holes: when will linear acceleration end?

[gneill]

I was musing about black hole mergers and what an observer might see for a particularly simple (i.e. blatantly contrived) scenario.

Suppose that there are two (non rotating, un-charged, bog standard) black holes of dissimilar masses heading for a head-on collision. They will accelerate towards each other. The larger one will accelerate at a lesser rate than the smaller one, but the acceleration of both towards each other can be observed.

As they merge, will a distant observer see a change in the acceleration of the bodies, and when the smaller black hole just disappears beneath the the event horizon of the larger black hole (admittedly creating a much larger event horizon for the combined masses), will there still be a perceived acceleration of the combination for some interval? If so, for how long might this observable acceleration persist?

Just curious.

 

[Drakkith]

Wouldn't this manifest as a 'wobble' of the new event horizon, or a 'ringdown'?

 

[gneill]

Wouldn't this manifest as a 'wobble' of the new event horizon, or a 'ringdown'?

Could be. I admit that I'm not up to scratch on the details of black hole interactions. The question arose from an idle curiosity. I was wondering how long after the BH's encountered each other that the perceived accelerations of their centers of mass could be detected.

I wonder how long would a "ringdown" persist? It's kind of a sneaky way of asking how long it takes for events below the event horizon to sort themselves out if that''s even a reasonable question. Probably not.

 

[Drakkith]

I wonder how long would a "ringdown" persist?

According to LIGO, less than 0.05 seconds passed from peak amplitude until the ringdown was no longer detectable in the first detected black hole merger. Perhaps it lasts a bit longer but just isn't detectable from this distance.

 

[gneill]

Very interesting. Thanks for that!