A Gamma ray burst associated with LIGO GW event

[Jeff Rosenbury]

Apparently we can expect this experimental Result to be repeated about Once every year ?

I'm curious why?

The rapidity of the first observation would indicate lots more to come, but with a sample size of one, even that's just a guess/hope.

Given how big space is, these might be going off all the time, but probably not as large/strong and perhaps most of them are undetectable with current detectors.

I'm guessing budget increases might give better equipment and more data.

 

[Drakkith]

Two highly confident observations of an event within microseconds of each other.

Well, within 400,000 microseconds of each other...

 

[looking4sophia]

I'm curious why?

The rapidity of the first observation would indicate lots more to come, but with a sample size of one, even that's just a guess/hope.

Given how big space is, these might be going off all the time, but probably not as large/strong and perhaps most of them are undetectable with current detectors.

...

I am pretty sure I read they expect maybe 1 BH Merger event Per Year, but can not find the article.
I'll keep looking
I was wrong about it being thousands of Light Years away. It was over 1 BILLion Light Years out there.

I did find this article that says the GWave carried away 3 Solar Masses of ENergy in less than 1 Second
making it 10 times more Powerful than all the stars in the observable Universe for that brief moment.

http://www.ligo.org/science/Publication-GW150914/index.php

This Article also answered a question I had concerning the Surface of the Hour Glass Shaped merger.

They said the Surface Oscillated before settling into a Sphere.
This Oscillation may be part of the Acceleration and Deceleration that induces a GWaves and Frequencies.

 

[looking4sophia]

I did find an Estimate, that the space based eLISA proposed for launch in 2034,
could detect as many as 35 GWave events over a 3 Year period from MASSIVE Bianary Black Hole Mergers
with another 55 less Massive mergers at too high frequencies to be observe by eLISA.

This higher Estimate of ~10 to 12 Events per Year may be due to eLISA having really long arms to detect changes in Length due to GWs.

https://en.wikipedia.org/wiki/Evolved_Laser_Interferometer_Space_Antenna

" The LISA concept has a constellation of three spacecraft , arranged in an equilateral triangle with million-kilometre arms (5 million km for classic LISA, 1 million km for eLISA) ... The distance between the satellites is precisely monitored to detect a passing gravitational wave. "

 

[looking4sophia]

Interesting Simulation of 2 Neutron Stars merging into a BH

 

[looking4sophia]

More dramatic Views of 2 Neutron Stars as they 'Ringdown' into a Singularity.

Seems some portion of the Fuel Rich remnants of these 2 stars
would reach Critical Mass conditions Inside the Event Horizon
so their released Energy in the form of Light photons etc..
would be Trapped by the BH ?

 

[Jeff Rosenbury]

More dramatic Views of 2 Neutron Stars as they 'Ringdown' into a Singularity.

Seems some portion of the Fuel Rich remnants of these 2 stars
would reach Critical Mass conditions Inside the Event Horizon
so their released Energy in the form of Light photons etc..
would be Trapped by the BH ?

As I understand it, there is no "inside" the event horizon. However infalling stuff tends to heat up and speed up flinging some mass/energy out of orbit. (Conservation of angular momentum causes some of this.)

 

[Jonathan Scott]

Note that for the LIGO GW event analysis of the wave indicated that the two masses involved were well over the theoretical maximum mass for a neutron star so they are assumed to be already black holes, not neutron stars.

 

[Ken G]

There is an "inside" the EH, it's all the stuff that could never avoid being pulled into the singularity. Also, neutron stars would not normally be regarded as fuel rich, though once inside the EH it wouldn't matter.

 

[nikkkom]

neutron stars would not normally be regarded as fuel rich

For conditions like those on neutron stars, even thermonuclear fuels have rather modest energy densities. When they burn, 1% of their mass converted to energy? Phew, when *any matter* (even completely inert as fuel - say, iron) falls onto a neutron star, ~20% of its rest mass gets converted to energy on impact. This potential well is *that deep*. Even just rearranging matter (and/or EM field) on a neutron star surface into a "slightly" less energetic configuration unleashes a mother of all solar flares.

A neutron star being shredded by a black hole ought to emit a torrent of gamma rays.

 

[looking4sophia]

Thanks for the clarifications above.
I also saw that an "accretion disc' acts like a 'traffic jam' or 'firewall' as some have described it ;
Before any gas or dust can even reach the EH.

Apparently 'spaggetification' also happens outside the EH due to the tremendous G gradient ??

 

[Nugatory]

Apparently 'spaggetification' also happens outside the EH due to the tremendous G gradient ??

You can strike the word "also" - spaghettification is the result of tidal forces (caused by the gradient) which increase without bound as you approach the event horizon - so any body, no matter how rigid, will spaghettify somewhere above the horizon on the way through. Conversely, a sufficiently non-rigid body can be spaghettified by even the weaker forces around an gravitating object that is not a black hole.

 

[Ken G]

Not quite-- the tidal forces increase without bound (theoretically) as you approach the singularity, not the event horizon. The EH has no local significance. Indeed, for very large black holes, like supermassive black holes in galaxy centers, there is no significant spaghettification at the EH. The significance of the EH is only a matter of global geometry, all forward timelike paths inside the EH connect globally to the singularity. But the local spacetime there is mundane, on scales small enough compared to the EH.

 

[Mantuano]

That FGrB may be the energy and info expelled by the reduction of apparent "surface" of both black holes when merging into one of less total "surface" than the sum of both individually considered. But we have no means to re-translate it into a significant info. Sure, g-waves do travel at light speed, but, once again, we do not know how is that the g-mediator, call it graviton or whatever, does exit the black hole. This is a problem that will laast a while to be solved.

 

[Mantuano]

Do a fast acceleration of any celestial bodies( black holes) produce gravitational waves?

Any periodic moving mass produces a g-wave. because the deformation of s-t is locally related to its mass. Only, the intensity of that wave is correspondingly infinitesimal as compared with a black hole or a neutron star or for that, a normal star. MO.

 

[Jonathan Scott]

That FGrB may be the energy and info expelled by the reduction of apparent "surface" of both black holes when merging into one of less total "surface" than the sum of both individually considered. But we have no means to re-translate it into a significant info. Sure, g-waves do travel at light speed, but, once again, we do not know how is that the g-mediator, call it graviton or whatever, does exit the black hole. This is a problem that will laast a while to be solved.

Firstly, what do you mean by the reduction of apparent "surface"? Black holes (rather counter-intuitively) scale linearly in size with mass, so any "surface" scales with the square of the mass, so the "surface" of a merged combination in that sense is greater than the surface of the separate black holes.

And secondly, nothing has to exit the black hole; the gravitational field of the black hole forms during its formation. Only changes need to propagate anywhere, and there are no changes occurring inside the event horizon.

 

[Jonathan Scott]

That FGrB may be the energy and info expelled by the reduction of apparent "surface" of both black holes when merging into one of less total "surface" than the sum of both individually considered...

And thirdly, although the apparent gamma ray burst was small compared with the total energy of the black holes, it would still require a very substantial amount of energy having to escape. This suggested mechanism doesn't seem to be anywhere near on the right scale.

 

[Mantuano]

I did use quoted "surface" to mean the equivalent of the event horizon surface. which is less than linearly summed,.after they merge The final surface of the event horizon is the surface corresponding to the quadratic sum of the masses, which is different than the square of the final mass, as clearly may be seen. Tthat difference has to be explained somwhow in terms of info and energy being expelled or annihilated otherwise. And this has to occur just at merging time

 

[Mantuano]

Firstly, what do you mean by the reduction of apparent "surface"? Black holes (rather counter-intuitively) scale linearly in size with mass, so any "surface" scales with the square of the mass, so the "surface" of a merged combination in that sense is greater than the surface of the separate black holes.

And secondly, nothing has to exit the black hole; the gravitational field of the black hole forms during its formation. Only changes need to propagate anywhere, and there are no changes occurring inside the event horizon.

 

[Mantuano]

With respect to g-field / s-t shrinkage occurring at the time of black hole collapsing from a mass suitable to it, the field / s-t shrinking already were around the body, so it looks as being a sudden discontinuity in value of that g-field / deformation, unless a different unknown effect is in operation.

 

[Jonathan Scott]

I did use quoted "surface" to mean the equivalent of the event horizon surface. which is less than linearly summed,.after they merge The final surface of the event horizon is the surface corresponding to the quadratic sum of the masses, which is different than the square of the final mass, as clearly may be seen. Tthat difference has to be explained somwhow in terms of info and energy being expelled or annihilated otherwise. And this has to occur just at merging time

I'm still puzzled as to what you mean here by "less than linearly summed". (a + b)^2 = a^2 + b^2 + 2ab which is always greater than a^2 + b^2. OK, there are complications relating to spinning and angular momentum, but the general rule is that the event horizon radius scale for the black hole is proportional to mass.

 

[Jonathan Scott]

With respect to g-field / s-t shrinkage occurring at the time of black hole collapsing from a mass suitable to it, the field / s-t shrinking already were around the body, so it looks as being a sudden discontinuity in value of that g-field / deformation, unless a different unknown effect is in operation.

Sorry, I don't understand what you're saying here. Gravitational waves are the most sudden thing that can happen to the field, and those propagate at c. Apart from those, the distant field is unaffected by collapse to a black hole.

 

[jhart]

I'm essentially a layman so I fully expect the answer to this to be "no", but since the energy that is supposed to have gone into the production of the GW in GW150914 has been estimated by LIGO as 3 solar masses is there no known mechanism for some of that energy to be converted back into mass locally and thus produce this GRB?

I'm thinking of the massive local distortions in space. Could vast Gravitational Waves separate virtual particles into pairs? Something similar to the "Schwinger effect"?

If something like that was a big enough effect to produce a GRB that we could detect then the energy lost to the GWB would presumably have to be taken into account in the model for the event itself?

 

[Jonathan Scott]

I'm essentially a layman so I fully expect the answer to this to be "no", but since the energy that is supposed to have gone into the production of the GW in GW150914 has been estimated by LIGO as 3 solar masses is there no known mechanism for some of that energy to be converted back into mass locally and thus produce this GRB?

The fact that the apparent GRB was only about half a second after the GW event places some strong constraints on possible mechanisms. Unless there are further unlikely coincidences involved, this suggests that the source of the GRB was only at most a fraction of a light second away from the merger event (noting for comparison that the radius of the sun is about 2.3 light seconds).

 

[jhart]

The fact that the apparent GRB was only about half a second after the GW event places some strong constraints on possible mechanisms. Unless there are further unlikely coincidences involved, this suggests that the source of the GRB was only at most a fraction of a light second away from the merger event (noting for comparison that the radius of the sun is about 2.3 light seconds).

Yes, that's why I was thinking of some interaction with virtual particles. As I understand it the problem people have with both these events being connected is that there should not be enough normal matter within 0.4 light seconds of the merger (I got this from Nature Vol 531 page 431 "But most observers now consider it to be a coincidence...our astrophysical expectation has been that the gas from stars that formed the binary black hole has long dispersed".)

But what I am thinking is that 3 Solar Masses is a very large amount of energy, if there is any mechanism to convert some of it back into matter, or directly into photons, within the first 0.4 seconds that could account for the GRB.

Then I thought: There are ways to exchange energy with "the vacuum",could that be it?

If spacetime in the region of the merger is being stretched and compressed at 250 Hz and presumably the local wave strain is very high, would that be enough for pair production by the separation of virtual particles?

I then had a quick, and probably naive look at virtual particles on wikipedia and found this: "Another example is pair production in very strong electric fields, sometimes called vacuum decay. If, for example, a pair of atomic nuclei are merged to very briefly form a nucleus with a charge greater than about 140, (that is, larger than about the inverse of the fine structure constant, which is a dimensionless quantity), the strength of the electric field will be such that it will be energetically favorable to create positron-electron pairs out of the vacuum or Dirac sea, with the electron attracted to the nucleus to annihilate the positive charge. This pair-creation amplitude was first calculated by Julian Schwinger in 1951." (https://en.wikipedia.org/wiki/Virtual_particle#Pair_production).

Which is why I added the Schwinger effect to my original post, if a strong electric field can produce that effect then presumably it's possible for a large GW strain to do the same thing? I.e. create conditions where pair production is energetically favorable.

If this happened then I would expect the GW to lose energy separating the virtual particles into pairs. That energy would then be converted into photons when then particles annihilated with whatever partner they could find.

That might not be the mechanism, it's just a wild guess on my part. But maybe there is some other mechanism that could take energy back out of the GWs and dump it into the local space.

 

[Jonathan Scott]

The local energy density in a gravitational wave, even close to the source, is many orders of magnitude smaller than the energy density typically involved in gamma ray production.

I personally find it very implausible that there could be any mechanism by which gravitational wave energy could be converted to gamma rays. My own conclusion would have to be that if the GRB is real, then whatever events were involved in creating the GW also separately resulted in creating the GRB.

 

[jhart]

The local energy density in a gravitational wave, even close to the source, is many orders of magnitude smaller than the energy density typically involved in gamma ray production.

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?

Am I missing something?

 

[Jonathan Scott]

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?

Am I missing something?

I haven't checked your figures, but that seems plausible. Although that's an extremely high energy density compared with everyday experience, the key point is that for a gravitational wave the energy is evenly distributed with a density of something like that order of magnitude. To produce gamma rays, you have to have interactions involving particles with energies in MeV (or temperatures of bulk matter with corresponding kinetic energy), but I don't believe that gravitational waves could impart local energies anywhere near on that scale.

A well-known process which generates gamma ray flashes is when an accumulation of material on the surface of a neutron star undergoes chain reaction fusion, and in general the temperature of a neutron star where there is a lot of infalling material can reach gamma-ray levels, although the luminosity of such events wouldn't be enough to explain the visibility at such a distance.

As far as I know, the apparent GRB would be be similar to that expected from a neutron star collision at that distance, but of course that is not consistent with the theoretical model which expects objects of the observed masses to be black holes.

 

[jhart]

... but I don't believe that gravitational waves could impart local energies anywhere near on that scale.

Fair enough! Thanks for your answers!

 

[newjerseyrunner]

I have a sort of out there hypothesis: What if one of the two objects that collided wasn't a black hole, there are other theoretical objects out there with the mass way beyond neutron stars. Cosmic strings are theoretically capable of producing both a gravitational wave and gamma ray bursts: http://news.nationalgeographic.com/...erse-cosmic-strings-gamma-ray-bursts-physics/