“Even if the Fermi detection is a false alarm, future LIGO events should be monitored for accompanying light irrespective of whether they originate from black hole mergers. Nature can always surprise us.” -Avi Loeb

Ever since LIGO first announced the direct detection of gravitational waves from two merging black holes, the physics and astronomy community has been struggling to understand an unexpected phenomenon that appears to have come along with it: a short-period gamma ray burst.

An artist’s impression of two stars orbiting each other and progressing (from left to right) to merger with resulting gravitational waves. This is the suspected origin of short-period gamma ray bursts. Image credit: NASA/CXC/GSFC/T.Strohmayer.

An artist’s impression of two stars orbiting each other and progressing (from left to right) to merger with resulting gravitational waves. This is the suspected origin of short-period gamma ray bursts. Image credit: NASA/CXC/GSFC/T.Strohmayer.

Arriving just 0.4 seconds after the gravitational waves did, the Fermi satellite’s detection doesn’t line up with models of black hole mergers. It’s thought that short-period GRBs originate from neutron star-neutron star mergers, and so seeing this has led to speculation of new physics, including from Avi Loeb at Harvard that perhaps LIGO’s twin black holes came from inside the same star. However, this explanation is exceedingly unlikely, and there are a number of astrophysical explanations that don’t require the new physics that Loeb’s explanation would.

Image credit: Image credit: NASA, ESA and G. Bacon (STScI), of a binary black hole. Loeb’s idea is that these binary black holes could exist inside a single star.

Image credit: Image credit: NASA, ESA and G. Bacon (STScI), of a binary black hole. Loeb’s idea is that these binary black holes could exist inside a single star.

Go get the whole — mostly critical — story of why LIGO’s black holes probably didn’t come from the same star!

Comments

  1. #1 Sinisa Lazarek
    February 25, 2016

    Forbes’ crap wall is back again, so can’t read the article and there is no link to the paper in overview. My question is.. how can 2 black holes come from a single mass source and be separated?

  2. #2 SelfAwarePatterns
    selfawarepatterns.com
    February 25, 2016

    My assumption with the two-black-holes-in-one-star theory was that the star was in the process of complete collapse, causing the GRB, but that, due to its extremely high rotation speed, it had an intermediate stage where two black holes formed in a dumbell configuration, which then proceeded to merge causing the gravitational waves.

  3. #3 EpiPete
    February 25, 2016

    Sinisa:

    arxiv.org/abs/1602.04735

  4. #4 Omega Centauri
    February 25, 2016

    SelfAware: That was the impression I got from reading the dumbed-down for the public version I saw. So if I understood it right, this dualBH would have a very short lifetime, as its almost already in the merger phase when formed. And there would still be several solar masses worth of dense stuff around it. Sounded like a really cool idea, if it makes physical sense.

    I think the idea was enough rotation of the stellar core that collapses into a hole that bifurcates at formation due to too much angular momentum. But between GR radiation and interaction with the rest of the star, the angular momentum is quickly lost, so the dual BH phase is very transitory.

    I’ll let the experts battle it out, as to whether thats a reasonable scenario.

  5. #5 Sinisa Lazarek
    February 26, 2016

    Thanx EpiPete

  6. #6 Sinisa Lazarek
    February 26, 2016

    after quickly going over the paper, am not really convinced. It seems that 4-5 very unusual things had to happen in very coincidental manner in order for this to be even plausible.

    A huge star, more than 100Mo.. very low metalicity, yet surviving 5 billion years of stellar evolution.. spinning almost out of bounds.. yet just right.. and then several other things need to be just right.. not really observed or much theorized before.. and then.. yes.. this is more likely than 2 BH mergers.. because of a single gamma ray burst.

    I’m much more inclined to think our understanding of black hole mergers is so-so.. and gamma ray burst happen during mergers despite our model, then a single star with so many “almost-impossible-to-find-in-same-place” properties as to be a contender. Time will tell…

  7. #7 Wow
    February 26, 2016

    We DO have 100 billion suns in 100 billion galaxies.

    I think we have plenty of room for a long shot to occur.

  8. #8 PJ
    Perth, west Oz
    February 26, 2016

    If there were 2 BHs, would there have been signs of a ‘ring up’ prior to the merger showing the ‘ring down’ in the plots ?

  9. #9 Sinisa Lazarek
    February 26, 2016

    @ Wow

    that’s true as well.

  10. #10 Sinisa Lazarek
    February 26, 2016

    Why IMO this is unlikely is that while I can imagine such a star existing.. i.e. Eta Carinae is similar.. with such a mass and volitility of the star.. as described in the paper.. one would expect GRB’s coming from that region long before the Ligo event. Yet no events were.. A huge star, spinning extremely rapidly should be “buzzing” like crazy.

  11. #11 Wow
    February 26, 2016

    There are several options as to what is going on, and given no better handle on their probabilities, you can only claim each are equally as unlikely, therefore any one of them is probably not the actual situation (given that we observe this, there must be something explaining the observation).

    So I agree it’s probably not this, but we’re not really at the moment at the stage of saying what is going on, nor even what is likely going on. We’re at what is POSSIBLY going on.

    And it could possibly be this.

    (heck, just off the top of my head, a scenario of a huge star that contains a large black hole that merged with it billions of years ago would make the star last longer than it “ought”. Working out if it’s feasible would require some work to figure out the likely masses, working through the model to see the results and seeing if there’s a way of making it fit the observation.

    And it would still be, even if it passed that, a possible answer.

    To find out what’s liable to be right, you need to find out what other feature would distinguish them all, and you need to work out the possible models to test for first.

    I’m at the stage of “that’s interesting”. A long way from making a claim of supportable assertion. As are these scientists, though to get media copy you need to be more assertive,because academia is too wishy-washy for media consumption.

  12. #12 Omega Centauri
    February 26, 2016

    What I was thinking when I read it, was a more or less an ordinary core collapse supernova, only with too much
    angular momentum to directly create a single BH. If that is the case than the dual BH formation and merge is part of the SN cum gamma-ray-burst process for high angular momenta stars. I can’t imagine a star containing a BH to last for anything longer than a few seconds.

  13. #13 Wow
    February 26, 2016

    If our sun had a solar mass black hole in its centre, it would burn for at least 5 billion years longer than it would otherwise have lasted.

    Remember, there’s only so fast things can lose energy to fall into the black hole’s event horizon, and that limits the rate of infall of matter, whilst the doubled mass means it would retain cohesion and not reach nova instability because the nuclear fusion would have to overcome a bigger force to eject material in a nova event.

    Black holes don’t suck things in. It doesn’t work like it does in futurama. That’s a cartoon.

  14. #14 ray
    usa
    April 14, 2016

    Gravitational waves is not reality same as black holes .Yes,I am aware this is a strong statement and needs a world of backing in this case there`s universal support from each and every single object within our universe of which is powered by sunlight. There`s visible proof of a universe powered by sunlight and not gravity.The claim is gravity keeps the planets around the sun,this discovery shows it is done by sunlight.check it out at –youtube– sunlight electro rays

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