Doubling the Detection of FRB's :

[beecee]

https://phys.org/news/2018-10-aussie-telescope-mysterious-fast-radio.html

Aussie telescope almost doubles known number of mysterious 'fast radio bursts'

October 10, 2018, International Centre for Radio Astronomy Research

Australian researchers using a CSIRO radio telescope in Western Australia have nearly doubled the known number of 'fast radio bursts'— powerful flashes of radio waves from deep space.

The team's discoveries include the closest and brightest fast radio bursts ever detected.

Their findings were reported today in the journal Nature. 

Fast radio bursts come from all over the sky and last for just milliseconds.

Scientists don't know what causes them but it must involve incredible energy—equivalent to the amount released by the Sun in 80 years.

"We've found 20 fast radio bursts in a year, almost doubling the number detected worldwide since they were discovered in 2007," said lead author Dr. Ryan Shannon, from Swinburne University of Technology and the OzGrav ARC Centre of Excellence.

"Using the new technology of the Australia Square Kilometre Array Pathfinder (ASKAP), we've also proved that fast radio bursts are coming from the other side of the Universe rather than from our own galactic neighbourhood."

Co-author Dr. Jean-Pierre Macquart, from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR), said bursts travel for billions of years and occasionally pass through clouds of gas.

Read more at: https://phys.org/news/2018-10-aussie-telescope-mysterious-fast-radio.html#jCp

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the paper:

https://www.nature.com/articles/s41586-018-0588-y

The dispersion–brightness relation for fast radio bursts from a wide-field survey:

 

Abstract:

Despite considerable efforts over the past decade, only 34 fast radio bursts—intense bursts of radio emission from beyond our Galaxy—have been reported1,2. Attempts to understand the population as a whole have been hindered by the highly heterogeneous nature of the searches, which have been conducted with telescopes of different sensitivities, at a range of radio frequencies, and in environments corrupted by different levels of radio-frequency interference from human activity. Searches have been further complicated by uncertain burst positions and brightnesses—a consequence of the transient nature of the sources and the poor angular resolution of the detecting instruments. The discovery of repeating bursts from one source3, and its subsequent localization4 to a dwarf galaxy at a distance of 3.7 billion light years, confirmed that the population of fast radio bursts is located at cosmological distances. However, the nature of the emission remains elusive. Here we report a well controlled, wide-field radio survey for these bursts. We found 20, none of which repeated during follow-up observations between 185–1,097 hours after the initial detections. The sample includes both the nearest and the most energetic bursts detected so far. The survey demonstrates that there is a relationship between burst dispersion and brightness and that the high-fluence bursts are the nearby analogues of the more distant events found in higher-sensitivity, narrower-field surveys5

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So, what is our best guess as to what these FRB's are......The instant a mass collapses to a BH? Neutron star/s collisions? and how are they related to GRB's? Any other suggestions?

 

[DrP]

1 hour ago, beecee said:

So, what is our best guess as to what these FRB's are......The instant a mass collapses to a BH? Neutron star/s collisions? and how are they related to GRB's? Any other suggestions?

What causes 2 stars to collide? Two galaxies passing through each other? I always wondered what happens when 2 galaxies pass through each other - presumably many of the stars just go right through due to the space between then, but some must collide with great velocity. Would this do it? Could the SMBH in the centre crash? - that must be so rare though I doubt they would detect 20 a year....  although the universe is a big place and has been around for quite a while.

 

Sorry to crash your great thread with my naïve questions - it isn't my field at all, but it is obviously fascinating.

[beecee]

13 minutes ago, DrP said:

What causes 2 stars to collide? Two galaxies passing through each other? I always wondered what happens when 2 galaxies pass through each other - presumably many of the stars just go right through due to the space between then, but some must collide with great velocity. Would this do it? Could the SMBH in the centre crash? - that must be so rare though I doubt they would detect 20 a year....  although the universe is a big place and has been around for quite a while.

 

Sorry to crash your great thread with my naïve questions - it isn't my field at all, but it is obviously fascinating.

It's thought that with the actual great distances between stars, that stellar collisions are relatively rare galaxies do merge. But when speaking of the universe and the numbers of galaxies out there, "rare"takes on a whole new meaning. Consider also that so far aLIGO and VIRGO have detected 5 BH collisions and 1 Neutron star/s collisions. 

Your inquiries welcome by the way and no naivity detected at all....thanks.

Edited October 11, 2018 by beecee

[beecee]

So, what is our best guess as to what these FRB's are......The instant a mass collapses to a BH? Neutron star/s collisions? and how are they related to GRB's? Any other suggestions?

Any suggestions? Obviously these FRB's happened a long long time ago, in a galaxy/s far far away.

[mistermack]

Since the cause is unknown, I'll feel free to speculate. I don't think it's due to stars colliding. I remember reading somewhere that when galaxies collide, the space between the stars is so vast, compared to the size of the stars, that the whole galaxies just pass through each other with no collisions being likely. And anyway, surely the clue is in the briefness of the FRB ? Stars colliding might happen quick, but surely not milliseconds? 

My guess is that it's something to do with gravitational lensing. Just for an instant, the conditions might be just right to perfectly concentrate a lot of energy in our direction. Milliseconds later, it's pointing elsewhere. 

But I can't imagine why it's coming from other regions and not ours. Maybe it's due to conditions that prevailed in the past, which are rare now. 

[DrP]

On ‎13‎/‎10‎/‎2018 at 9:45 PM, beecee said:

Any suggestions? Obviously these FRB's happened a long long time ago, in a galaxy/s far far away.

Death Star explosions!? 

 

On ‎14‎/‎10‎/‎2018 at 1:08 PM, mistermack said:

I don't think it's due to stars colliding. I remember reading somewhere that when galaxies collide, the space between the stars is so vast, compared to the size of the stars, that the whole galaxies just pass through each other with no collisions being likely. And anyway, surely the clue is in the briefness of the FRB ? Stars colliding might happen quick, but surely not milliseconds? 

I don't know how long it takes...  but I was thinking along the lines of 2 stars from different galaxies passing through each other colliding head on at super velocity - the explosion would be immense and I would think some strange shit could happen on the nuclear level. Like an intergalactic collider.  

You are probably right though that it is something else.  Do we know what to expect to detect from 2 stars striking head on from different galaxies passing through each other at speed in the range of some fraction of C?

 

[mistermack]

I'm guessing as much as anyone on this. There as so many variables when you think of two stars colliding. The odds are hugely against it, given the distances involved, and if it did happen, it could be a near miss with transference of material, or a glancing blow, or a direct hit. But the odds against a direct hit would be huge, so it's the least likely of all the instances. I've never read what would happen. There are binary stars, I don't know if they resulted from a collision, or not. 

[DrP]

9 minutes ago, mistermack said:

But the odds against a direct hit would be huge, so it's the least likely of all the instances. I've never read what would happen.

I guess it would be speculation as to what happens. It is certainly not 'impossible' for 2 stars travelling at relative speeds that are some fraction of C to hit head on.   Regarding the odds though - as beecee mentioned, there are SO many galaxies in such a vast amount of space that have been spinning about for over 14 billion years... 'rare' becomes quite probable in this expanse. It just 'has' to have happened at some point...  and if that was far enough away we would only just see it happening....  or it could have happened and we will not even see it for another 10 million years or more.

 

On ‎11‎/‎10‎/‎2018 at 11:18 AM, beecee said:

.... But when speaking of the universe and the numbers of galaxies out there, "rare"takes on a whole new meaning. Consider also that so far aLIGO and VIRGO have detected 5 BH collisions and 1 Neutron star/s collisions. 

5 BH collisions in just a few years.... Does this point to it being more common that we might have thought?

OK - C is around 671 Million mph according to google.  The speed of our galaxy is about 0.5 Million mph. So lets say the average relative head on velocity of a galaxy collision is aprox 1 million mph.    That's 1/671 of C.   Do we know from colliders what happens to nuclei that collide head on at 1/671 of C - what types of radiation would that give off?  Radio? With 2 stars passing directly though each other, with so much mass and substance I would assume some head on collisions  -  not sure how many would be needed to produce the type of FRBs detected but could it be speculated at?

With regard to milli seconds for the event - well - it would be over pretty quickly at 1/671 of C. Assuming a spherical propagation of the radiation from the impact site across such a vast distance would we expect it to last more than a few milli seconds?

 

[mistermack]

2 hours ago, DrP said:

I guess it would be speculation as to what happens. It is certainly not 'impossible' for 2 stars travelling at relative speeds that are some fraction of C to hit head on.   Regarding the odds though - as beecee mentioned, there are SO many galaxies in such a vast amount of space that have been spinning about for over 14 billion years... 'rare' becomes quite probable in this expanse. It just 'has' to have happened at some point...  and if that was far enough away we would only just see it happening....  or it could have happened and we will not even see it for another 10 million years or more.

It's not impossible as you say. But another reason I would doubt it is that if that was the cause, you would expect FRBs to be generated at a similar rate in our own region, but they say that they are all coming from far away. We have galaxies colliding locally so why not any local FRBs?

In fact the Milky Way and Andromeda are due to collide in about four billion years time, and there are various visible galaxies that are colliding right now.   https://en.wikipedia.org/wiki/NGC_2207_and_IC_2163    

Wiki says that when the Milky Way and Andromeda do "collide" it's unlikely that any individual stars will collide.

[beecee]

On 10/14/2018 at 11:08 PM, mistermack said:

 And anyway, surely the clue is in the briefness of the FRB ? Stars colliding might happen quick, but surely not milliseconds? 

I'm still with the instant any massive object collapses to and beyond its Schwarzchild limit. Sort of like a last gasp before the BH is formed.

[mistermack]

When a black hole evaporates, you get a massive release of energy. I don't think it's ever been witnessed. They have to be below a certain size because the rate of evaporation slows down with increasing mass. I think the prediction is of a gigantic gamma ray burst, but maybe an FRB could be triggered as well or instead. It's theorised to happen in a tiny sliver of time.

[beecee]

36 minutes ago, mistermack said:

When a black hole evaporates, you get a massive release of energy. I don't think it's ever been witnessed. They have to be below a certain size because the rate of evaporation slows down with increasing mass. I think the prediction is of a gigantic gamma ray burst, but maybe an FRB could be triggered as well or instead. It's theorised to happen in a tiny sliver of time.

The smallest BH's possible from stellar/Neutron star collapse is from memory about 3 solar masses and they would take some incredible unbelievable length of time to evaporate....around 10 to the 100 power years or similar. I'm ignoring the possible existence of micro/quantum size BH's that may have been created at or a short time after the BB.

Done some checking at https://www.quora.com/What-is-the-explosion-power-of-a-micro-black-hole-when-they-evaporate-and-how-did-you-find-the-answer

So according to the generally trusted answers from that site, micro BH's would have already evaporated, and so FRB's could certainly be evaporating micro/quantum BH's due to their place of origin being many billions of year away and which we are just witnessing.

Edited October 17, 2018 by beecee

[Strange]

It is hypothesised that "primordial" black holes could have been formed in the early universe and be small enough to be evaporating now. However, searches have yet to find any, and they don't appear to be similar to FRBs.

http://www.astronomy.com/news/2018/02/the-search-for-primordial-black-holes-continues

[mistermack]

That's how I remember it, gamma rays being predicted. Could it be though, that gamma rays from tens of billions of light years away might now be radio waves due to red shift? ( I'm just musing, I haven't searched for the answer )