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Old 13-01-2018, 12:40 AM
gary
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Highly polarized electromagnetic radiation from FRB 121102 might betray its source

In a 12 Jan 2018 article in the Sydney Morning Herald, Liam Mannix
reports on how the highly polarized electromagnetic radiation from
a Fast Radiation Burst source, FRB 121102, might provide a clue as to
its origin.

Quote:
Originally Posted by Liam Mannix, Sydney Morning Herald
The team that made the discovery have been studying FRB 121102, an FRB source unique because its signal keeps repeating over and over.

They called in Dr Sobey, an expert in the rotation of light, when they noticed the signal had a unique attribute: extreme polarisation.

...

More unusually, the light had been "twisted", she says, hitting the Earth like a corkscrew. This is usually caused by light moving through an extremely strong magnetic field generated by a field of dense ionised gas, known as plasma.

The FRB's polarisation points to one of two sources.

Most likely, the bursts are being generated by a tiny but energetic star that has become trapped within the dense plasma cloud of a powerful nebula. The star's polarised light is being twisted by the surrounding plasma before it reaches us.

That, or the star is trapped near a super-massive black hole, which could produce similar effects.
Article here :-
http://www.smh.com.au/technology/sci...11-h0gx8d.html

Article also at Nature :-
https://www.nature.com/news/mysterio...source-1.21235

Quote:
Originally Posted by Alexandra Witze, Nature
Astronomers have pinpointed the location of an enigmatic celestial object that spits out brief, but powerful, blasts of radio waves. Surprisingly, the source of these intermittent signals lies not in a bright galaxy but in a small, dim one, some 2.5 billion light-years from Earth.

The discovery begins to lift the curtain on the mystery of fast radio bursts, which have puzzled astronomers since they first described the signals in 20071. “This detection has really broken open the gates of a new realm of science and discovery,” says Sarah Burke-Spolaor, an astronomer at the National Radio Astronomy Observatory in Socorro, New Mexico, and West Virginia University in Morgantown. She spoke in Grapevine, Texas, at a meeting of the American Astronomical Society.
Quote:
Originally Posted by Alexandra Witze, Nature
The latest work, published on 4 January in Nature, is the sharpest look yet at the home of a fast radio burst known as FRB 121102. Located in the constellation Auriga, the intermittent signal was first detected on 2 November 2012. Since then, it has flared up several times, making it the only fast radio burst known to repeat.

A team led by Shami Chatterjee, an astronomer at Cornell University in Ithaca, New York, began with the 305-metre-wide Arecibo radio telescope in Puerto Rico. Its sensitivity allowed the scientists to detect multiple bursts from FRB 121102. The team then used two sets of radio telescopes — the Karl G. Jansky Very Large Array in New Mexico, and the European VLBI Network across Europe — to narrow down the location of FRB 121102 even further.

The bursts originate from a dwarf galaxy that emits faint radiation in both radio and visual wavelengths. Follow-up observations with the Gemini North telescope, on Mauna Kea, Hawaii, showed that it is less than one-tenth the size and has less than one-thousandth the mass of the Milky Way.

”The host galaxy is puny,” says team member Shriharsh Tendulkar, an astronomer at McGill University in Montreal, Canada. “That's weird.” With fewer stars than many galaxies, dwarf galaxies would seem to have less of a chance of hosting whatever creates fast radio bursts. That would include neutron stars, one of the leading candidates for the source of fast radio bursts.

But much more work is needed to pin down the physical mechanism of what causes these mysterious bursts, says Chatterjee. For now, FRB 121102 is just one example.

That need could be filled later this year when a new radio telescope comes online in British Columbia, Canada, dedicated to hunting fast radio bursts.
The discovery has also been reported in papers in Nature (subscription required) :-
https://www.nature.com/articles/nature25149

http://www.nature.com/articles/nature20797
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Old 13-01-2018, 02:55 PM
xelasnave's Avatar
xelasnave
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Thank you Gary very interesting stuff.
Alex
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