Fast Radio Bursts

[John Clark]

Today in the Journal Science it was announced that for only the second time the pinpoint location of a Fast Radio Burst (FRB) has been found, one of the most mysterious things in astronomy that probably require new physics to explain. This FRB came from the outskirts of a old massive galaxy with little new star formation which was very unlike the first the FRB which came from the center of a young dwarf galaxy with lots of stellar formation, and that  indicates FRB's are a general phenomena not requiring unusual astronomical conditions. 

Only about 60 FRB's have ever been observed, mostly in the last 5 years, but the location of only 2 have been found. They only last about a millisecond but produce as much energy as the sun does in 80 years and most never repeat so they're hard to detect much less precisely locate, but it's estimated that about 10,000 must happen every day in the observable universe. Theories have been proposed for their cause but all the ones I've heard involve very weird stuff of one sort or another.  

A single fast radio burst localized to a massive galaxy

John K Clark

[Lawrence Crowell]

It sort of makes sense this might involve magnetars. If a neutron star with a huge magnetic field, ~ 10^{10}T, collides with another neutron star or black hole the sudden reconfiguration of the magnetic field might send a huge electromagnetic pulse. Of course hypothetical statements could at this time easily be wrong.

LC 

[John Clark]

On Sat, Jun 29, 2019 at 1:59 PM Lawrence Crowell <goldenfield...@gmail.com> wrote:

> It sort of makes sense this might involve magnetars. If a neutron star with a huge magnetic field, ~ 10^{10}T, collides with another neutron star or black hole the sudden reconfiguration of the magnetic field might send a huge electromagnetic pulse.

Maybe, but to me that seems like a explanation of Gamma Bay Bursts, FRB's are something different, a single immensely powerful millisecond radio pulse with no accompanying gamma, X-ray or optical emissions. Of the 60 known FRB's most never repeat but 2 of them have which would rule out any sort of catastrophic collision, at lest for those two, but we may be dealing with two different phenomenon with two different underlying mechanisms.  

One idea involves a very rapidly rotating neutron star of more than 2.2 solar mass but less than 2.7,  normally such a thing would collapse into a Black Hole but not if its spinning fast enough; however its its powerful magnetic field would gradually slow it down and when it reached a critical point it would collapse and form a Black Hole and maybe produce a radio pulse. But of course something like that couldn't repeat and at least 2 FRB's do. 

Another idea for the cause involved the decay of  Axion Miniclusters, but of course they couldn't repeat either:

Fast Radio Bursts and Axion Miniclusters

Yet another weird idea involve superconducting cosmic strings, maybe that could repeat.

Superconducting cosmic strings as sources of cosmological fast radio bursts         

John K Clark

 

 

 

[smitra]

On 29-06-2019 22:44, John Clark wrote:
> On Sat, Jun 29, 2019 at 1:59 PM Lawrence Crowell
> <goldenfield...@gmail.com> wrote:
>

>> _> It sort of makes sense this might involve magnetars. If a neutron

>> star with a huge magnetic field, ~ 10^{10}T, collides with another
>> neutron star or black hole the sudden reconfiguration of the

>> magnetic field might send a huge electromagnetic pulse._

>
> Maybe, but to me that seems like a explanation of Gamma Bay Bursts,
> FRB's are something different, a single immensely powerful millisecond
> radio pulse with no accompanying gamma, X-ray or optical emissions. Of
> the 60 known FRB's most never repeat but 2 of them have which would
> rule out any sort of catastrophic collision, at lest for those two,
> but we may be dealing with two different phenomenon with two different
> underlying mechanisms.
>
> One idea involves a very rapidly rotating neutron star of more than
> 2.2 solar mass but less than 2.7, normally such a thing would
> collapse into a Black Hole but not if its spinning fast enough;
> however its its powerful magnetic field would gradually slow it down
> and when it reached a critical point it would collapse and form a
> Black Hole and maybe produce a radio pulse. But of course something
> like that couldn't repeat and at least 2 FRB's do.
>
> Another idea for the cause involved the decay of Axion Miniclusters,
> but of course they couldn't repeat either:
>

> Fast Radio Bursts and Axion Miniclusters [1]

>
> Yet another weird idea involve superconducting cosmic strings, maybe
> that could repeat.
>
> Superconducting cosmic strings as sources of cosmological fast radio

> bursts [2]
>

Or perhaps a process that leads to emission along a narrow beam. The
power of the source can then be much less and you can then occasionally
get repeat events from the same source.

Saibal

[Lawrence Crowell]

The first paper in the section on electrodynamics proposes how this would happen. The first section involves a lot of phenomenology I am not familiar with. Equations 6 throught 8 give the modified Maxwell equations. There is in addition a wave equation for the axion. The axion obeys a Klein-Gordon equation with an EM inhomogenous term such as

(□ + m^2) φ = -gE·B

Which has the solution for a stationary phase Ã(x,t) = Ã(x)e^{-iωt} has an approximate solution

φ(x,t) ≈ φ_0exp(-i√{k^2 - m^2}x)e^{-iωt} + e^{-i√(gE·B/φ_0)t}

I think that is ok as a back of envelope calculation. One would really need to work this out coupled with the Maxwell equations. For axions in a large magnetic field they will be converted into EM radiation.

Axions are a fair prospect for dark matter. They are thought to have been slowed in a sort of “quantum molasses” that caused these very light particles, maybe as little as 10^{-11} times the mass of the electron, to “freeze” into clumps. They are a candidate for dark matter which composes a galactic halo. So far tests have eliminated a number of axion mass ranges. Why these would suddenly burst seems odd.

For the second paper it is interesting that people are still thinking about cosmic strings. They started to fade from attention 10 to 15 years ago. There does not appear to be a lot of astrophysical evidence for them. However, maybe some form of them does exist.

LC