Gamma ray burst associated with LIGO GW event

[Jonathan Scott]

The wave profile from the GW observation showed two compact objects. Even if cosmic strings exist (which I doubt), I don't think they would behave as compact objects, and their gravitational effect is not at all like that of a conventional object.

 

[newjerseyrunner]

I have another set of questions, is there any data on how old the two objects that collided were? And how would a massive, double lobed star like Eta Carinae die? I could imagine an instability in a star like that causing one lobe to collapse or explode, which would catastrophically destabilize the other lobe. I could easily imagine a star that big with a shape such as that quickly turning into a double-black hole pair that would very quickly merge. The black holes would exist for only a short period of time, but still produce a gravitational wave. During this time, there would still be a massive amount of material that has not fallen into the hole yet, that could easily produce a gamma ray burst, which would come after the gravity event due to having to get through all of that material.

EDIT: Bah! I thought about it for a bit, the events I described would explain the gravity wave and gamma ray, but would also require a burst of neutrinos a little before the gravity wave event during the actual collapse. Was there any detection of neutrino blasts?

 

[Jonathan Scott]

From the shape of the GW, we can determine the masses of the objects (basically by simulating various theoretical models and seeing which ones fit best). From the point at which the "ring down" phase started (where the objects started to merge), we can place limits on their sizes. From the amplitude of the wave, we can determine the approximate distance of the event. From the time difference between the two detectors and other phase information we can identify areas of the sky from which the signal probably originated. Everything up to that point was beautifully consistent with two black holes spiralling together and merging.

I don't think we have any other information about the GW event itself.

We then have the unexpected apparent GRB.

As mentioned at the start of this thread, one of the speculative theories to explain the GRB is that the pair of black holes merged inside a star, so you might find that paper interesting.

However, I think the answer to your specific question about double-lobed stars is outside the scope of this thread, and quite possibly too speculative for discussion within these forums unless you can find any suitable references.

 

[Jonathan Scott]

Was there any detection of neutrino blasts?

There was no detection of any neutrino emissions above normal background levels.

For general information about the event, try the Wikipedia page: https://en.wikipedia.org/wiki/First_observation_of_gravitational_waves

 

[jhart]

I have another set of questions, is there any data on how old the two objects that collided were? And how would a massive, double lobed star like Eta Carinae die? I could imagine an instability in a star like that causing one lobe to collapse or explode, which would catastrophically destabilize the other lobe. I could easily imagine a star that big with a shape such as that quickly turning into a double-black hole pair that would very quickly merge. The black holes would exist for only a short period of time, but still produce a gravitational wave. During this time, there would still be a massive amount of material that has not fallen into the hole yet, that could easily produce a gamma ray burst, which would come after the gravity event due to having to get through all of that material.

EDIT: Bah! I thought about it for a bit, the events I described would explain the gravity wave and gamma ray, but would also require a burst of neutrinos a little before the gravity wave event during the actual collapse. Was there any detection of neutrino blasts?

The Eta Carinae system has a semi-major axis of 15.4 AU, why would they "very quickly merge"? Black Hole pairs will orbit teach other just like any other pair of objects with the same mass. There are factors, such as the Gravitational Waves themselves, that mean the time to merger will be different from that of two stars orbiting each other, but from what I have read there is no reason to suppose these two Black Holes could not have existed for 100s of millions of years before the merger.

The issue with the GRB comes from the proposal that a Black Hole pair of this size would normally be expected to form either as the result of a binary system of very large, low-metallicity stars which, independently, underwent supernova, or from two independently formed black holes which migrated together in a dense star cluster. See my earlier reference to Nature vol 531, according to that feature it is expected that, in the dense star cluster scenario, the Black Hole binary would be ejected from the cluster at high speed. Later in the same feature it says that any gas around at the formation of the Black Holes should have dispersed before they merge.

More data should help and hopefully we won't have to wait long. Once a 3rd observatory is up and running the area of the sky they need to search for GRBs will be reduced and if they see Black Hole mergers are normally not accompanied by GRBs then this one can presumably be put down to coincidence or some freak accident of formation like the merger inside a star concept.

On the other hand if every Black Hole merger is accompanied by a GRB then presumably they have to come up with new hypotheses.

 

[nikkkom]

Isn't that energy density in this case 3 x the mass of the Sun x c² / ((4/3) x π x (0.4xc)³)?

Which is approx 5.4 x 10⁴⁷ J / 7.2 x 10²⁴ m³

I.e. about 7.4 x 10²² J/m³ right?

Is that really smaller than the energy density typically involved in gamma ray production?

That's equivalent to almost a thousand tons of mass/energy equivalent crammed into that poor, tortured cubic meter of space. I find it not at all implausible there is an "insignificant" effect we miss or underestimate today which turns "small fraction" of that energy to EM radiation.

 

[jhart]

That's equivalent to almost a thousand tons of mass/energy equivalent crammed into that poor, tortured cubic meter of space. I find it not at all implausible there is an "insignificant" effect we miss or underestimate today which turns "small fraction" of that energy to EM radiation.

If it turns out that there is I'm going to say "called it" :) Especially if the mechanism is some kind of interaction with virtual particles.

 

[Jonathan Scott]

That's equivalent to almost a thousand tons of mass/energy equivalent crammed into that poor, tortured cubic meter of space. I find it not at all implausible there is an "insignificant" effect we miss or underestimate today which turns "small fraction" of that energy to EM radiation.

For comparison, I think that's something like 10^11 times smaller than the mass of the corresponding volume of neutron star material, which is definitely able to emit gamma rays.

 

[nikkkom]

Gamma rays in magnetar flares are emitted by "empty" space filled by magnetic fields, when those fields shift into a slightly less energetic configuration. However, those fields are 10-100 times denser than this too.

 

[jhart]

Gamma rays in magnetar flares are emitted by "empty" space filled by magnetic fields, when those fields shift into a slightly less energetic configuration. However, those fields are 10-100 times denser than this too.

Of course I'm estimating the "density" based on the 0.4 second time difference between the GW event and the GRB, so I'm thinking that this is a minimum energy density. To heap further unjustifiable speculation on: it could be that there was a delay between the GW energy being converted into mass and the mass being converted into photons which would make the volume in which that happened smaller.

 

[Jonathan Scott]

As far as I know, there is no known mechanism by which gravitational waves could give rise to electromagnetic waves in empty space. There is of course no definitive theory which covers both gravity and quantum effects, but one would not expect to get anywhere near quantum effects in this situation, as the energy density is many orders of magnitude lower than that involved for example in neutron stars.

It would be difficult to extract much energy from a gravitational wave into a solid object. As I said before, if the GRB is real, it seems it must have been created separately as part of some aspect of the merger event, not driven by the gravitational wave.

Black holes are not supposed to be able to maintain any significant magnetic fields (unlike neutron stars in general, and certainly unlike magnetars), so magnetic field effects are not expected to be relevant.

 

[newjerseyrunner]

I wonder if there is some way to pin down which event actually happened first. The gravity wave getting to us before the GRB doesn't necessarily mean that that's the order it happened in.

Black holes are not supposed to be able to maintain any significant magnetic fields (unlike neutron stars in general, and certainly unlike magnetars), so magnetic field effects are not expected to be relevant.

Don't spinning black holes produce some of the very powerful magnetic fields?

A large amount of plasma being held by a magnetic field of one of them, suddenly being released by the reconfiguration of the fields by the merger?

 

[Jonathan Scott]

I wonder if there is some way to pin down which event actually happened first. The gravity wave getting to us before the GRB doesn't necessarily mean that that's the order it happened in.

I don't know what you have in mind, but I can't think of any plausible scenario which could be associated with any other order, although as I've already said, it is more likely that both had a common cause rather than the GW in some way giving rise to the GRB.

Don't spinning black holes produce some of the very powerful magnetic fields?

No, that's neutron stars (especially magnetars).

There are ideas that a black hole could somehow retain a "frozen" magnetic field from a precursor body, but I don't think that's considered mainstream at present.

 

[newjerseyrunner]

I don't know what you have in mind, but I can't think of any plausible scenario which could be associated with any other order, although as I've already said, it is more likely that both had a common cause rather than the GW in some way giving rise to the GRB.

I was suggesting that they actually happen at or near the same time, but the light took longer to reach us that the gravity wave. Light is slowed by matter and gravity waves are not. A black hole forming would actually produce a gravity wave, then a very short time later, a neutrino blast, then several hours later a gamma ray blast, even though all three events happened at the same time. Obviously not the case here, just explaining why I don't think we should take the time delta to mean much right now.

No, that's neutron stars (especially magnetars).

There are ideas that a black hole could somehow retain a "frozen" magnetic field from a precursor body, but I don't think that's considered mainstream at present.

Interesting.

 

[jhart]

I was suggesting that they actually happen at or near the same time, but the light took longer to reach us that the gravity wave. Light is slowed by matter and gravity waves are not. A black hole forming would actually produce a gravity wave, then a very short time later, a neutrino blast, then several hours later a gamma ray blast, even though all three events happened at the same time. Obviously not the case here, just explaining why I don't think we should take the time delta to mean much right now.

Intergalactic space is so nearly devoid of matter that the gamma rays would probably arrive before the neutrinos. Neutrinos have mass (see https://en.wikipedia.org/wiki/Neutrino#Mass) current estimate is 0.32 eV. Photons are expected to be massless and the current upper bound set by experiments is 10^-18eV.

Over 750 million light years a Neutrino with a kinetic energy of 7 MeV should, if the 0.32 eV figure is correct, be slowed down by about 40 minutes.

In 1987 there was a famous supernova, SN 1987A, in the LMC about 168,000 Light Years away. A burst of neutrinos was observed, but they arrived essentially at the same time as the photons. It did allow physicists to set an upper limit to the neutrinos mass of 16eV.

I can't find anything useful on the refractive index of inter galactic space, but based on the number density of Hydrogen atoms, which is less than 1 per cubic meter, a photon could travel about 10,000 light years before interacting with a single Hydrogen Atom even assuming it interacts with every Hydrogen Atom it passes. Let's say that slows it down by an average of a millisecond, that works out at 75 seconds over 750 million light years. I think that is probably way too high, but it's enough for me to think that the photons should arrive before the neutrinos.

 

[nikkkom]

As far as I know, there is no known mechanism by which gravitational waves could give rise to electromagnetic waves in empty space.

What would happen if that space is not exactly empty? BHs sometimes have accretion disks. Inspiraling BH pair may have an accretion disk which encompass both BHs at once. The inner portion of the disk is quite hot, it's a plasma. Plasmas exhibit various complex EM properties.

 

[newjerseyrunner]

In 1987 there was a famous supernova, SN 1987A, in the LMC about 168,000 Light Years away. A burst of neutrinos was observed, but they arrived essentially at the same time as the photons. It did allow physicists to set an upper limit to the neutrinos mass of 16eV.

This is incorrect, there was a three hour difference in the neutrino blast from the photon blast from SN 1987A, the neutrinos got here first.

When a star explodes, the explosion creates both neutrinos and photons at the same time. Neutrinos do not interact with matter (much) so they go straight through the star at nearly the speed of light. Photons, however, once they're created, they immediately get absorbed by the rest of the matter in the star. It has to propagate thousands of miles of plasma in order to get out, so it trails far behind the neutrinos.

That's why I think the GRB and the gravitational wave may have been created at the same time inside of a lot of matter. The X-ray would fall behind the gravity wave due to interaction.

 

[Jonathan Scott]

What would happen if that space is not exactly empty? BHs sometimes have accretion disks. Inspiraling BH pair may have an accretion disk which encompass both BHs at once. The inner portion of the disk is quite hot, it's a plasma. Plasmas exhibit various complex EM properties.

Yes, accretion disk materials could emit gamma rays during a BH collision. However, the maximum amount of energy that could be emitted from such diffuse materials is thought to be orders of magnitude too small to account for a GRB visible at that distance (if it is real).

 

[Eimacman]

I was reading this thread and I just thought of something just off the top of my head, so this may not fit the observations. Could the data be caused by a asymmetric core collapse supernova with neutron star of black hole kick out, with the blast toward the observer. The black hole or neutron star core would be traveling away from the observer. Several variables would have to be taken into account, such as; the degree of asymmetry of the blast and angle, the speed and angle of the receding core, and if the core is a black hole or a neutron star.

Eimacman

 

[rootone]

...just thought of something ,,,

Maybe

 

[Eimacman]

Upon further reflection, I believe that if this the case that with an asymmetrical blast towards the observer that the neutrinos and gamma rays might arrive simultaneously. There would be an associated gravitational distortion from the mass associated with the blast and core receding from each other, this might also arrive at the observer at the same time.

Eimacman

 

[Ken G]

It isn't a supernova. A supernova puts most of its energy into kinetic energy of the explosion, a little into light, and very very little into gravitational waves.

 

[Eimacman]

Greetings Ken G:

Are you speaking of a symmetrical supernova or asymmetrical? A symmetrical supernova will do as you stated most of its energy will kinetic some of which will be converted into elements heaver than iron and thus will not produce the data observed. However an asymmetrical supernova does not occur like a symmetrical supernova. In a symmetrical supernova the plasma layers collapse onto the core of iron, and is heated to billions of degrees, the core collapses into a ball of neutrons or a black hole and the resulting shock wave blasts the rest of the star outward in all directions, if the core collapses into a black hole the accretion disk in the center of the star and rotation would cause jets of gamma rays to blast out of the poles. If this was the case the observations would detect neutrinos first then gamma rays next and no severe gravitational distortions that could be detected by the observer.

With this being said I stated that an Asymmetrical supernova could possibly cause such effects as was observed because when the iron core is formed, in this type, the inrush of plasma can start severe oscillations, oscillations that can literally blow the core out and away from the star wile the blast travels in the opposite direction. almost all of the energy possibly as much as 70% of the explosion could be directed towards the observer. Also the blast mass would carry away with it gamma rays, neutrinos and so on as well as causing gravitational distortions. This being that most of the mass of the blast heading towards the observer, and not in all directions, which could contain multiple solar masses, and the core being of multiple solar masses traveling in the opposite direction. If this is the case the observed blast would have the neutrinos and gamma rays arriving at about the same time. And being that the outer shell of the star would be traveling in the observer's direction and the core is traveling away in the opposite direction, like a bullet from a gun, there might be sufficient gravitational distortions that could be detected at the same time as well.

Now with that said, if the blast was directed away from the observer it is unlikely that any thing could be seen at all, with the possibility of any gravitational waves that might have resulted might be detected as it would be to two massive objects rapidly moving away from each other and not colliding.

Eimacman

 

[Jonathan Scott]

The gravitational wave pattern requires a quadrupole source, not just "oscillations", and it closely matches predictions for two extremely dense objects orbiting in free space with energy and angular momentum being lost primarily through gravitational radiation. And there were no excess neutrinos detected.

 

[Eimacman]

Greetings Jonathan Scott:

You make an interesting point. But before I consider myself in error (which I most likely am) I must give this more thought and study. I am partly in error in that this may not have been, and is most likely not, an asymmetrical supernova event. I had not considered the oscillation of the core as a the main source of gravitational distortion even though at the end the core reaches escape velocity and displacement being as high as approximately π/2 stellar radii before the core is ejected. Is it possible that this could be quadrupole with a completely different four dimensional geometry? Has anyone considered this point and worked out the mathematics that would prove or disprove this? Is it possible that large displacements through the 4D that are caused by super-dense massive objects in an in spiraling orbit, have necessary geometry to be detected by the LIGO instrumentation?

Eimacman

 

[Drakkith]

Has anyone considered this point and worked out the mathematics that would prove or disprove this?

No one here. I doubt such calculations would be easy and there's little reason to believe that the extremely good fit the model has with the data is incorrect. Not if the folks at LIGO, along with others who investigated all of this before them, knew what they were doing.

Is it possible that large displacements through the 4D that are caused by super-dense massive objects in an in spiraling orbit, have necessary geometry to be detected by the LIGO instrumentation?

I'm sorry, I don't know what this means. What are "displacements through the 4d?"

 

[Eimacman]

Greetings Drakkith:

Displacements of gravitational distortion through the axis x, y, z, and t of four dimensional space time. I apologize that I did not make that clear.

Unfortunately without the mathematics I can not explain further to clear up this point one way or the other.

Eimacman

 

[Drakkith]

Displacements of gravitational distortion through the axis x, y, z, and t of four dimensional space time. I apologize that I did not make that clear.

What are "displacements of gravitational distortion"?

 

[Eimacman]

What are "displacements of gravitational distortion"?

Greetings:

Perhaps displacement is too nautical a term to use here, therefore I will give the mathematical equivalent: Δx, Δy, Δz, Δt; caused by a gravitational field.

I prefer to use the term 'gravitational distortion' in that bending, stretching, or pulling space-time is not an accurate description of gravitational effects on space-time.

I hope that clears up that point.

Eimacman

P.S. I am still studying the LIGO data, it is an interesting 'read' haven't quite 'got a handle' on the mathematics yet.

 

[Drakkith]

Perhaps displacement is too nautical a term to use here, therefore I will give the mathematical equivalent: Δx, Δy, Δz, Δt; caused by a gravitational field.

I prefer to use the term 'gravitational distortion' in that bending, stretching, or pulling space-time is not an accurate description of gravitational effects on space-time.

I hope that clears up that point.

So you're asking about gravitational waves? Looking at your earlier post:

Is it possible that large displacements through the 4D that are caused by super-dense massive objects in an in spiraling orbit, have necessary geometry to be detected by the LIGO instrumentation?

It appears you're asking whether or not LIGO can detect the gravitational waves generated by in-spiraling massive objects. Is that correct?