Phil has a nice post discussing the recent press release on a binary system of supermassive holes identified by Todd Boroson and (CV commenter) Tod Lauer.
Go check it out!
This is a rather nice finding, but it is not the first example of two close orbiting supermassive black holes. The pair in OJ 287 have a period of about 12 years and the orbital elements have been modeled from a light curve that goes back roughly a century. See
I just read about this and it occurred to me that no one, apparently, has observed any binary stellar-mass black holes. There seem to be quite a few X-ray binary systems (presumably a star orbiting a black hole, which is accreting matter from the star) harboring near-certain black hole candidates, so it seems conceivable that more massive binary partners could exist on the stellar scale. Then again, I’ve not heard of any neutron star-BH binaries being discovered, either. Are such systems thought to be out there in some number, but maybe not easily detectable (e.g. a binary BH may have little matter available for accretion, making them difficult to see)?
“Tod” is , of course, the German word for ‘Death'; just fyi
I guess I could phrase my question even more specifically: Are gravity wave detectors the only means by which one might expect to observe stellar-mass black hole binaries?
In answer to the point about OJ 287: There are a number of other candidates for “binary” supermassive black holes. There are objects like 3C75 and NGC 6240 that may have two black holes but the separation is kiloparsecs. We’ll have to wait a long time before we know whether they will become bound systems and merge, so you might question whether they should be called binaries. The other class are things like OJ 287, in which the evidence that there are two black holes is much less direct and less certain. In OJ 287, semi-periodic variations in brightness are interpreted as being due to one black hole passing near (or through) the accretion disk of the other, causing bursts of radiation. However, in my opinion, this model has become somewhat contrived without any good way to test it. The nice thing about this new one is (a) the presence of two sets of broad lines is pretty conclusive evidence that two supermassive black holes are involved, and (b) changes that would confirm the binary nature of the object and allow us to refine the orbit should be visible within a few years.
Another interesting candidate is 4C37.11, for which a beautiful double 21cm HI absorption profile is detected, see http://arxiv.org/abs/0902.0863
“Tod” is , of course, the German word for ‘Death’; just fyi.
Oh, okay, I see. I thought the second ‘d’ in Tod Lauer’s name had been pulled into Todd Boroson’s accretion disc.
Todd and I were able to work together on this, despite a fundamental disagreement about the d-count… Tod is especially nasty with my last name, which is German, in its German meaning. However, I depend on the true old-english source of Tod, the word for fox, as is evident in the last name Todhunter or Tadhunter. Fortunately, I turned down Ted William’s and Tad Pryor’s invitation to apply to the Rutger’s astronomy faculty…
Todd, just to be fair to OJ287, the authors had made a prediction of when the
next set bursts would happen, if this model was a binary black hole they did happen around Sept. 2008 as predicted.
LMMI, I think you are right about gravitational wave detectors being about the only way (baring low probability events) to detect stellar mass black hole binaries. They certainly should exist, as we have a few well known examples of binary pulsars. Thus we know both observationally and theoretically that binary star systems can (sometimes) survive double supernova. The masses aren’t that different so the timescales for spiraling into each other should be long enough. But the hot-***** astrophysics types should probably weigh in on this also.
The final black hole decay produces either two (np=2) or four (np=4) quanta. The fundamental Planck mass is 1 TeV.
It may be interesting to the readers of this blog that there’s pretty solid evidence emerging
that this source is not a binary black hole at all, see ATEL 1955:
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