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Antennas of CSIRO's Australian SKA Pathfinder (ASKAP) radio telescope first picked up the Fast Radio Burst. Credit: CSIRO / Alex Cherney, Author provided
Fast radio bursts (FRBs) are just that – enormous blasts of radio waves from space that only last for a fraction of a second. This makes pinpointing their source a huge challenge.
Our team recently discovered 20 new FRBs using CSIRO's Australian Square Kilometer Array Pathfinder in the Western Australian outback, almost doubling the known number of FRBs.
In follow-up research, published today in The Astrophysical Journal Letters, we have taken one of these new detections – known as FRB 171020 (the day of the radio waves arrived at Earth: October 20, 2017) – and narrowed down the location to a galaxy close to our own.
This is the closest FRB detected (so far) but we still do not know what causes these mysterious radio bursts that can contain more energy than our Sun produces in decades.
Waves in space
As they travel through the galaxy and our own Milky Way before arriving at our telescopes.
The longer radio wavelengths are slower than the short wavelengths, meaning that there is a slight delay in the arrival of wavelengths.
This difference is the dispersion measure and indicates the amount of radio emission has traveled through.
FRB 171020 has the lowest dispersion of any FRBs detected so far. That means it is from astronomical standards.
By using models of the distribution of matter in the universe we can put a hard limit on how far the radio signal has traveled. For this particular FRB, we estimate that it could not be more than a billion light years away. (Our Milky Way Galaxy is about 100,000 light years across.)
This distance limit, combined with the sky area, we know the FRB came from (an area half a square degree or roughly two full Moons across) enormously narrows down to the galaxy.
Closing in
This region typically contains hundreds of galaxies. We used giant optical telescopes in Chile – including the appropriately named Very Large Telescope and Gemini South – to derive distances to these galaxies by measuring their distance directly from us.
This is a possible limitation of the possible galaxies within the distance limit to just 16.
By far the closest, most likely to host the FRB, is a spiral galaxy called ESO 601-G036. This is 120 million light years away – making this one.
Optical image of the search area from the Digitized Sky Survey (DSS). The circles mark possible host galaxies for FRB 171020, but these are all much more than the most probable galaxy ESO 601-G036, shown in the lower left as a three-color image from the VLT Survey Telescope (VST) ATLAS survey. Credit: ESO, Digitized Sky Survey and VST-ATLAS, Author provided
FRBs: FRB 121102. FRBs. FRBs: FRB 121102.
This FRB is also known as the repeating FRB due to its – so far unique – property of producing multiple bursts. This helped astronomers locate it to more than 3 billion light years away.
ESO 601-G036 is similar in size, and forming new stars at the same rate, as the host of FRB repeating.
But there is one intriguing feature of the repeating that we do not see in ESO 601-G036.
Other emissions
In addition to repeat bursts of radio emission, the repeating FRB emits lower energy radio.
Using CSIRO's Australia Compact Array Telescope (ATCA) in Narrabri, NSW, we have searched for this persistent radio emission in ESO 601-G036. If it was anything like the repeater's galaxy, it should have a boomingly bright radio source in it. We saw nothing.
Not only did we find that ESO 601-G036 does not have any persistent radio emissions, but there are no other galaxies in our search volume that show similar properties to that seen in the repeating FRB.
This points to the possibility that there are different types of fast radio bursts that may have different origins.
Finding the galaxies that FRBs originates from a big step towards solving the mystery of these extreme bursts. Most FRBs travel much further distances so you find yourself in the world of FRBs in unprecedented detail.
The hunt for more
Unfortunately, we can not say with absolute certainty that ESO 601-G036 is the galaxy that FRB 171020 came from.
The next big hurdle in understanding what causes is to pinpoint more of them. If we can do that we will not be able to do that
If FRBs occur within the central nuclei of galaxies Or do they prefer the outskirts of galaxies? Gold regions where do you have new stars? There are still so many unknowns about FRBs.
Several radio telescopes around the world are commissioning systems to pinpoint bursts. Our study has shown that it is possible to combine these two phenomena with galaxies, and that it is possible to determine these causes FRBs.
Explore further:
Aussie telescope almost doubles famous number of mysterious 'fast radio bursts'
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