An international team of astronomers has discovered a permanently active second fast radio burst, raising questions about the nature of the mysterious phenomenon.
Fast radio bursts (FRB) are intense, brief flashes of radio frequency emissions, lasting on the order of milliseconds. The phenomenon was discovered in 2007 by graduate student David Narkevic and his supervisor Duncan Lorimer. The source of these highly energetic events is a mystery, but clues to their nature are slowly being collected.
The new source, fast radio burst 20190520B, was detected with the Five Hundred Meter Aperture Spherical Radio Telescope (FAST) in Guizhou, China on May 20, 2019 and found in data in November of the same year, a new study (opens in a new tab)reports.
Follow-up observations by the Very large painting by Jansky (VLA) led by Caltech found weaker and constant radio emissions associated with the FRB, also allowing the Subaru Telescope in Hawaii to locate the source within the confines of a dwarf galaxy about 3 billion light-years from Earth.
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This is notably the second repetitive FRB discovered associated with a persistent radio source (PRS), after the location of FRB 121102 in 2012.
“The big surprise for me was realizing that the new FRB appears to be a perfect ‘twin’ to an earlier discovery,” Casey Law, a Caltech astronomer and co-author who led the VLA program, told Space.com .
“Perhaps some would have preferred to say that the first association of this kind [between an FRB and radio source] was a coincidence, because it was hard to explain. Now, the second example shows that this is a real and essential part of an FRB’s life.”
This finding raises new questions about the nature of FRBs, such as whether FRB sources change over time, or whether different types of sources are capable of emitting FRBs.
“One of the key questions in the field of FRBs is whether all FRB sources repeat themselves,” said Di Li, of the National Astronomical Observatories of China (NAOC) and head of the Commensal Radio Astronomy FAST Survey (CRAFTS) which detected FRB 190520B. Space.com via email. “I personally favor an evolving picture as all sources repeat, but the level of activity drops precipitously as the source ages. Since FRB 20190520B is only the second of approximately 500 known FRBs to have a so-called PRS counterpart and both are extremely active, they could, in this hypothetical evolutionary picture, represent the youth of FRBs, which does not last very long.”
Another unique feature of FRB 190520B is its dispersion measurement, which indicates that its emissions passed through the highest electron density of any FRB before being observed on Earth. This suggests that the FRB is active in a local plasma environment, such as that created by a supernovaand is a newly created source.
While providing insight into FRB 190520B’s surroundings, the wide disparity in dispersion measurements with other FRBs calls into question their use as “cosmic measurements” for measuring distances.
Franz Kirsten, a postdoctoral researcher at the Netherlands Institute for Radio Astronomy (ASTRON) and Chalmers University in Sweden who was not involved in the research, told Space.com that an evolutionary path for FRBs is possible, but with just these two sources, it’s hard to tell.
“We need to find more and constrain this evolutionary stage model. We really need more at different ages to say okay, this thing is fading all the time,” Kirsten said. “So what would be really nice to see is if these persistent sources did indeed fade over time, say on time scales of 10 to 20 years. If we can say, okay, they are fading, so that’s definitely an indication that it’s a possibility.”
Following up on this research, co-author Yu Wenfei of the Shanghai Astronomical Observatory told Space.com that “the mechanisms responsible for the additional scatter measurement and near-source environment of these repetitive FRBs with a PRS association are the outstanding issues to follow”. and to solve.”
“I’m optimistic that the FRB puzzle will be solved by investigating such extreme FRBs,” Yu said.
Di also sees great value in discovering more repeating FRB sources, while trying to get a much better picture of the environments in which they occur, for example using the The Hubble Space Telescope for follow-up observations.
Cooperation between astronomers and facilities around the world will be crucial in finding, locating and characterizing these mysterious phenomena, as was the case with FRB 190520B.
“This discovery is impossible without international cooperation. FAST made the discovery and only VLA is able to locate it so effectively. Every instrument has its strength and we all have a sky,” says Di.
The study (opens in a new tab) was published online in the journal Nature Today (June 8).
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