Light shed on mystery space radio pulses , II Fast radio bursts: A mystery unfolds , II Mysterious series of fast radio bursts may have been twisted by extreme environment

The Very Large Array (VLA) radio telescope, which was used to track and study the location of FRB 121102, a series of mysterious light flashes. Scientists now think the bursts originated from a neutron star in an extreme environment (Dave Finley, NRAO/AUI/NSF) 

Astronomers watching a fast-radio burst flashing from more than 3 billion light-years away say that its source lies in an extreme environment with a powerful magnetic field — perhaps a supermassive black hole, or the remains of a supernova.

The findings about the phenomenon known as FRB 121102, described in the journal Nature and at the American Astronomical Society meeting outside Washington, hint that this mysterious source of powerful radio waves whose origin has puzzled scientists for years may finally be revealing its secrets.

Since their discovery in 2007 from older archived data, fast-radio bursts have confounded astronomers. These bursts last only milliseconds, shorter than the blink of an eye, but in that tiny moment they are incredibly bright, a sign that whatever caused them was very powerful.

"It's some sort of extreme physics that causes this emission and so the goal is to understand that," study coauthor Betsey Adams of ASTRON, the Netherlands Institute for Radio Astronomy, said at a briefing Wednesday.

The problem is that these bursts each only happen once — leading scientists to suspect that these were cataclysmic, death-throe explosions. So even if a telescope is lucky enough to catch one in the act of going off, there no way to go back to the same source for more detailed measurements.

FRB 121102, sitting about 3 billion light-years away in a dwarf galaxy, was different. Since its discovery in 2012 it has repeatedly sent out flashes of radio waves, allowing researchers to train their telescopes on it to learn more about its origins.

"We know of thirty sources of fast radio bursts, and this is the only one we've ever seen that repeats," senior author Jason Hessels, an astrophysicist at the University of Amsterdam and ASTRON, said in an interview.

Having now observed more than 100 flashes from this single source over the last few years, researchers haven't picked up a pattern to the bursts yet — aside from the fact that they often seemed to be clustered in time, instead of evenly spaced apart.

Because of the extremely short, repeated bursts, the source was thought to be a kind of neutron star: either a pulsar (which spins very fast) or a magnetar (which spins but also has an extra strong magnetic field). Because it seems to sit in a star-forming region of its host galaxy, the scientists think FRB 121102 is linked to stellar birth or death.

For this paper, the scientists wanted to figure out more about the environment around this source. Using data from the Arecibo Observatory in Puerto Rico and the Green Bank Telescope in West Virginia, the scientists looked at the polarization of the light: how much it's been distorted in specific ways. They found that radio waves have been twisted by a magnetic field — an extremely powerful one, judging from the degree of contortion.

"We've seen this effect in other fast radio burst sources before, but in this case the effect is 500 times larger than what we've seen at other sources," Hessels said. "That was quite surprising."

These kinds of polarization effects, he added, can be seen around powerful phenomena such as the supermassive black holes at the center of galaxies. That makes some sense for FRB 121102, since the ionized gas, or plasma, around the black hole could be responsible for the magnetic field that's twisting the neutron star's signal.

The researchers think these repeated fast radio bursts are coming from a pulsar that happens to be sitting near a growing supermassive black hole that's surrounded by gas and dust. But there are other possibilities: Perhaps a pulsar is interacting with the nebula from a dead star to create the strange repeat signal.

There are problems with both of those ideas, Hessel pointed out. If the neutron star's radio signal is being twisted by the plasma around a nearby supermassive black hole, why would such a massive black hole exist in such a small dwarf galaxy? And if it's being affected by a surrounding nebula, how did it get to be so bright?

Even the idea that the source itself is some kind of pulsar doesn't explain why the bursts are so clumped. Spinning neutron stars have highly regular periods.

It could also be that plasma is acting as a sort of lens, focusing the radio light and allowing us to see it clearly. (In the black-hole scenario, the plasma could be both polarizing and lensing the radio waves, Hessel said.) That could mean that the other fast radio bursts are also repeats, and we just haven't had a proper space lens that would allow us to see more than one.

Whatever its source, whatever its environment, and whether or not it is similar to the other one-shot fast radio bursts, understanding FRB 121102 will help astronomers to better understand the universe we live in, Hessels said.

After all, even though only a few dozen individual sources in total have been found, researchers estimate that perhaps 10,000 fast radio bursts flash across the night sky every single day. And just as a flashlight on a dark night can illuminate all the dust and fog particles in its beam, each of these radio bursts can reveal a little more of the contents of the space between the source and us.

Artist’s concept of radio waves from a fast radio burst, being observed by the Green Bank Telescope in West Virginia.

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Astronomers reported today (January 10, 2018) at the winter meeting of the American Astronomical Society (AAS) in Washington, D.C. on their recent studies of a mysterious source of fast radio bursts – three billion light-years away – known as FRB 121102. They said the source of the bursts must be:

… in an astonishingly extreme and unusual environment. This discovery suggests that the strange source is in the close vicinity of a massive black hole, or within a nebula of unprecedented power.

Their study is featured on the cover of the January 11, 2018 edition of the peer-reviewed journal Nature.

Visible-light image of the host galaxy of the fast radio burst FRB 121102. Image via NRAO/ Gemini Observatory/AURA/NSF/NRC.

FRB 121102 emits unpredictable bright pulses of radio emission, of extremely short duration (on the order of milliseconds). About 30 other sources of fast radio bursts, in other parts of the sky, are also known. But FRB 121102 is the only one known so far to repeat. That’s why – a year ago, at last winter’s AAS meeting – astronomers excitedly reported results of a breakthrough study, which had pinpointed FRB 121102’s location in the sky. Identifying its home galaxy, they said, would improve their chances of understanding the cause of the bursts.
Now, indeed, they do appear closer to that undertanding.

The new study on fast radio bursts is featured on the cover of the January 11, 2018 issue of the journal Nature.

In 2017, an international team of astronomers used two of the world’s largest radio telescopes – at the Arecibo Observatory in Puerto Rico, and the Green Bank Observatory in West Virginia – to show that the radio bursts from the source FRB 121102 have a property known as polarization. One statement explained:

The behavior of this polarized light allows them to probe the source’s environment in a new way and to `peer into the lair’ of the mysterious burster.
Polarized light is likely familiar to anyone who has used polarized sunglasses to cut down on the glare of sunlight reflected off water. If polarized radio waves travel through a region with a magnetic field, the polarization gets ‘twisted’ by an effect known as Faraday rotation: the stronger the magnetic field, the greater the twisting.
The amount of twisting observed in FRB 121102’s radio bursts is among the largest ever measured in a radio source, and the researchers conclude that the bursts are passing through an exceptionally strong magnetic field in a dense plasma (a hot, ionized gas).

Artist’s concept of a fast radio burst arriving at the Arecibo telescope in Puerto Rico.

Astronomer Daniele Michilli, who participated in the study, said:

The only known sources in the Milky Way that are twisted as much as FRB 121102 are in the galactic center, which is a dynamic region near a massive black hole. Maybe FRB 121102 is in a similar environment in its host galaxy.
However, the twisting of the radio bursts could also be explained if the source is located in a powerful nebula or supernova remnant.

With a number of wide-field radio telescopes now coming online, more such sources are expected to be discovered in the coming year, these astronomers said. They’re excited! And they’re poised to answer more fundamental questions about fast radio bursts.

National Radio Astronomy Observatory VLA fast radio burst animation from NRAO Outreach on Vimeo.
Bottom line: Astronomers reported on January 10, 2018 on their recent studies of the mysterious source of fast radio bursts – three billion light-years away – known as FRB 121102. They now think the bursts were twisted by the extreme environment around a supernova or supermassive black hole.

Image copyrightDR SETH SHOSTAK/SCIENCE PHOTO LIBRARY

Image captionThe analysis used data from the Arecibo Observatory in Puerto Rico

Astronomers have fresh insight on a mysterious source of recurring radio pulses from space.

Fast radio bursts (FRB) are one of the most persistent puzzles in astronomy. While usually short-lived, one source in the sky was sending out repeated flashes.
Now, a team says the strange emission could be caused by a dead star with an exceptionally powerful magnetic field.
Details were reported here at the 231st American Astronomical Society meeting.
The first FRB was discovered in 2007, in archived data from the Parkes Radio Telescope in Australia. Astronomers were searching for new examples of magnetised neutron stars called pulsars, but found a new phenomenon - a radio burst from 2001.
Since then, 18 FRBs - also referred to as "flashes" or "sizzles" - have been found in total.
The mystery surrounding their nature has spawned a variety of different possible explanations, from black holes to extra-terrestrial intelligence.
Only one of these sources of radio energy has erupted more than once - a so-called burster catalogued as FRB 121102. This FRB has sent out around 150 flashes since its discovery in 2012.
Now, in the journal Nature, a team of scientists explains how the emission might come from a neutron star, perhaps one near a black hole or one embedded in a nebula.

Twisted waves

The researchers found something interesting about the polarisation of the radio waves - which describes the direction in which they vibrate. When polarised radio waves pass through a region with a magnetic field, the polarisation gets "twisted" by an effect known as Faraday rotation. And the stronger the magnetic field, the greater the twisting.
"The only sources in the Milky Way that are twisted as much as FRB121102 are in the galactic centre, which is a dynamic region near a massive black hole. Maybe FRB121102 is in a similar environment in its host galaxy," said Daniele Michilli, a co-author from the University of Amsterdam.
"However, the twisting of the radio bursts could also be explained if the source is located in a powerful nebula or supernova remnant," he added.
Vishal Gajjar, from the Breakthrough Listen project and the Berkeley SETI Research Center, commented: "At this point, we don't really know the mechanism. There are many questions, such as, how can a rotating neutron star produce the high amount of energy typical of an FRB?"
The team used the Arecibo radio observatory in Puerto Rico and the Green Bank telescope in West Virginia to probe the source at higher frequencies than ever before.
Andrew Seymour, a staff astronomer at the Arecibo Observatory, said: "The polarisation properties and shapes of these bursts are similar to radio emission from young, energetic neutron stars in our galaxy. This provides support to the models that the radio bursts are produced by a neutron star."
A year ago, the research team pinpointed the location of FRB121102 and reported that it lies in a star-forming region of a dwarf galaxy at a distance of more than three billion light-years from Earth.
The enormous distance to the source implies that it releases a monstrous amount of energy in each burst - roughly as much energy in a single burst of one millisecond as the Sun releases in an entire day.

Astronomers watching a fast-radio burst flashing from more than 3 billion light-years away say that its source lies in an extreme environment with a powerful magnetic field — perhaps a supermassive black hole, or the remains of a supernova.

The findings about the phenomenon known as FRB 121102, described in the journal Nature and at the American Astronomical Society meeting outside Washington, hint that this mysterious source of powerful radio waves whose origin has puzzled scientists for years may finally be revealing its secrets.

Since their discovery in 2007 from older archived data, fast-radio bursts have confounded astronomers. These bursts last only milliseconds, shorter than the blink of an eye, but in that tiny moment they are incredibly bright, a sign that whatever caused them was very powerful.

"It's some sort of extreme physics that causes this emission and so the goal is to understand that," study coauthor Betsey Adams of ASTRON, the Netherlands Institute for Radio Astronomy, said at a briefing Wednesday.

The problem is that these bursts each only happen once — leading scientists to suspect that these were cataclysmic, death-throe explosions. So even if a telescope is lucky enough to catch one in the act of going off, there no way to go back to the same source for more detailed measurements.

FRB 121102, sitting about 3 billion light-years away in a dwarf galaxy, was different. Since its discovery in 2012 it has repeatedly sent out flashes of radio waves, allowing researchers to train their telescopes on it to learn more about its origins.

"We know of thirty sources of fast radio bursts, and this is the only one we've ever seen that repeats," senior author Jason Hessels, an astrophysicist at the University of Amsterdam and ASTRON, said in an interview.

Having now observed more than 100 flashes from this single source over the last few years, researchers haven't picked up a pattern to the bursts yet — aside from the fact that they often seemed to be clustered in time, instead of evenly spaced apart.

Because of the extremely short, repeated bursts, the source was thought to be a kind of neutron star: either a pulsar (which spins very fast) or a magnetar (which spins but also has an extra strong magnetic field). Because it seems to sit in a star-forming region of its host galaxy, the scientists think FRB 121102 is linked to stellar birth or death.

.

For this paper, the scientists wanted to figure out more about the environment around this source. Using data from the Arecibo Observatory in Puerto Rico and the Green Bank Telescope in West Virginia, the scientists looked at the polarization of the light: how much it's been distorted in specific ways. They found that radio waves have been twisted by a magnetic field — an extremely powerful one, judging from the degree of contortion.

"We've seen this effect in other fast radio burst sources before, but in this case the effect is 500 times larger than what we've seen at other sources," Hessels said. "That was quite surprising."

These kinds of polarization effects, he added, can be seen around powerful phenomena such as the supermassive black holes at the center of galaxies. That makes some sense for FRB 121102, since the ionized gas, or plasma, around the black hole could be responsible for the magnetic field that's twisting the neutron star's signal.

The researchers think these repeated fast radio bursts are coming from a pulsar that happens to be sitting near a growing supermassive black hole that's surrounded by gas and dust. But there are other possibilities: Perhaps a pulsar is interacting with the nebula from a dead star to create the strange repeat signal.

There are problems with both of those ideas, Hessel pointed out. If the neutron star's radio signal is being twisted by the plasma around a nearby supermassive black hole, why would such a massive black hole exist in such a small dwarf galaxy? And if it's being affected by a surrounding nebula, how did it get to be so bright?

Even the idea that the source itself is some kind of pulsar doesn't explain why the bursts are so clumped. Spinning neutron stars have highly regular periods.

It could also be that plasma is acting as a sort of lens, focusing the radio light and allowing us to see it clearly. (In the black-hole scenario, the plasma could be both polarizing and lensing the radio waves, Hessel said.) That could mean that the other fast radio bursts are also repeats, and we just haven't had a proper space lens that would allow us to see more than one.

Whatever its source, whatever its environment, and whether or not it is similar to the other one-shot fast radio bursts, understanding FRB 121102 will help astronomers to better understand the universe we live in, Hessels said.

After all, even though only a few dozen individual sources in total have been found, researchers estimate that perhaps 10,000 fast radio bursts flash across the night sky every single day. And just as a flashlight on a dark night can illuminate all the dust and fog particles in its beam, each of these radio bursts can reveal a little more of the contents of the space between the source and us.

Artist’s concept of radio waves from a fast radio burst, being observed by the Green Bank Telescope in West Virginia.

Astronomers reported today (January 10, 2018) at the winter meeting of the American Astronomical Society (AAS) in Washington, D.C. on their recent studies of a mysterious source of fast radio bursts – three billion light-years away – known as FRB 121102. They said the source of the bursts must be:

… in an astonishingly extreme and unusual environment. This discovery suggests that the strange source is in the close vicinity of a massive black hole, or within a nebula of unprecedented power.

Their study is featured on the cover of the January 11, 2018 edition of the peer-reviewed journal Nature.

 Visible-light image of the host galaxy of the fast radio burst FRB 121102. Image via NRAO/ Gemini Observatory/AURA/NSF/NRC.

FRB 121102 emits unpredictable bright pulses of radio emission, of extremely short duration (on the order of milliseconds). About 30 other sources of fast radio bursts, in other parts of the sky, are also known. But FRB 121102 is the only one known so far to repeat. That’s why – a year ago, at last winter’s AAS meeting – astronomers excitedly reported results of a breakthrough study, which had pinpointed FRB 121102’s location in the sky. Identifying its home galaxy, they said, would improve their chances of understanding the cause of the bursts.
Now, indeed, they do appear closer to that undertanding.

The new study on fast radio bursts is featured on the cover of the January 11, 2018 issue of the journal Nature.

 
In 2017, an international team of astronomers used two of the world’s largest radio telescopes – at the Arecibo Observatory in Puerto Rico, and the Green Bank Observatory in West Virginia – to show that the radio bursts from the source FRB 121102 have a property known as polarization. One statement explained:

The behavior of this polarized light allows them to probe the source’s environment in a new way and to `peer into the lair’ of the mysterious burster.
Polarized light is likely familiar to anyone who has used polarized sunglasses to cut down on the glare of sunlight reflected off water. If polarized radio waves travel through a region with a magnetic field, the polarization gets ‘twisted’ by an effect known as Faraday rotation: the stronger the magnetic field, the greater the twisting.
The amount of twisting observed in FRB 121102’s radio bursts is among the largest ever measured in a radio source, and the researchers conclude that the bursts are passing through an exceptionally strong magnetic field in a dense plasma (a hot, ionized gas).

Artist’s concept of a fast radio burst arriving at the Arecibo telescope in Puerto Rico.

Astronomer Daniele Michilli, who participated in the study, said:

The only known sources in the Milky Way that are twisted as much as FRB 121102 are in the galactic center, which is a dynamic region near a massive black hole. Maybe FRB 121102 is in a similar environment in its host galaxy.
However, the twisting of the radio bursts could also be explained if the source is located in a powerful nebula or supernova remnant.

With a number of wide-field radio telescopes now coming online, more such sources are expected to be discovered in the coming year, these astronomers said. They’re excited! And they’re poised to answer more fundamental questions about fast radio bursts.

National Radio Astronomy Observatory VLA fast radio burst animation from NRAO Outreach on Vimeo.
Bottom line: Astronomers reported on January 10, 2018 on their recent studies of the mysterious source of fast radio bursts – three billion light-years away – known as FRB 121102. They now think the bursts were twisted by the extreme environment around a supernova or supermassive black hole.

Image copyrightDR SETH SHOSTAK/SCIENCE PHOTO LIBRARY

Image captionThe analysis used data from the Arecibo Observatory in Puerto Rico

Astronomers have fresh insight on a mysterious source of recurring radio pulses from space.

Fast radio bursts (FRB) are one of the most persistent puzzles in astronomy. While usually short-lived, one source in the sky was sending out repeated flashes.
Now, a team says the strange emission could be caused by a dead star with an exceptionally powerful magnetic field.
Details were reported here at the 231st American Astronomical Society meeting.
The first FRB was discovered in 2007, in archived data from the Parkes Radio Telescope in Australia. Astronomers were searching for new examples of magnetised neutron stars called pulsars, but found a new phenomenon - a radio burst from 2001.
Since then, 18 FRBs - also referred to as "flashes" or "sizzles" - have been found in total.
The mystery surrounding their nature has spawned a variety of different possible explanations, from black holes to extra-terrestrial intelligence.
Only one of these sources of radio energy has erupted more than once - a so-called burster catalogued as FRB 121102. This FRB has sent out around 150 flashes since its discovery in 2012.
Now, in the journal Nature, a team of scientists explains how the emission might come from a neutron star, perhaps one near a black hole or one embedded in a nebula.

Twisted waves

The researchers found something interesting about the polarisation of the radio waves - which describes the direction in which they vibrate. When polarised radio waves pass through a region with a magnetic field, the polarisation gets "twisted" by an effect known as Faraday rotation. And the stronger the magnetic field, the greater the twisting.
"The only sources in the Milky Way that are twisted as much as FRB121102 are in the galactic centre, which is a dynamic region near a massive black hole. Maybe FRB121102 is in a similar environment in its host galaxy," said Daniele Michilli, a co-author from the University of Amsterdam.
"However, the twisting of the radio bursts could also be explained if the source is located in a powerful nebula or supernova remnant," he added.
Vishal Gajjar, from the Breakthrough Listen project and the Berkeley SETI Research Center, commented: "At this point, we don't really know the mechanism. There are many questions, such as, how can a rotating neutron star produce the high amount of energy typical of an FRB?"
The team used the Arecibo radio observatory in Puerto Rico and the Green Bank telescope in West Virginia to probe the source at higher frequencies than ever before.
Andrew Seymour, a staff astronomer at the Arecibo Observatory, said: "The polarisation properties and shapes of these bursts are similar to radio emission from young, energetic neutron stars in our galaxy. This provides support to the models that the radio bursts are produced by a neutron star."
A year ago, the research team pinpointed the location of FRB121102 and reported that it lies in a star-forming region of a dwarf galaxy at a distance of more than three billion light-years from Earth.
The enormous distance to the source implies that it releases a monstrous amount of energy in each burst - roughly as much energy in a single burst of one millisecond as the Sun releases in an entire day.