A research team led by California Institute of Technology astronomer Vikram Ravi and Curtin University research fellow Ryan Shannon has detected the brightest fast radio burst (FRB) to date, called FRB 150807.
The location of the FRB 150807. The yellow circle shows the typical location of an FRB. There are thousands of stars and galaxies in this direction. Because FRB 150807 was very bright the astronomers were able to locate it to a small region near the edge of that circle, shown as the pink banana-shaped region in the inset. In this region there are only six detected galaxies. The position of the most likely host galaxy, VHS7, is highlighted on the plot. Image credit: Vikram Ravi, California Institute of Technology / Ryan Shannon, ICRAR-Curtin & CSIRO.
FRBs are powerful radio flashes lasting just milliseconds, with mysterious origins that continue to be a matter of debate.
Only 18 FRBs have been detected to date. Most give off only a single burst and do not flash repeatedly.
Additionally, most FRBs have been detected with telescopes that observe large swaths of the sky but with poor resolution, making it difficult to pinpoint the exact location of a given burst.
The unprecedented brightness of FRB 150807 allowed the astronomers to localize it much more accurately, making it the best-localized FRB to date.
“We estimate that there are between 2,000 and 10,000 FRBs occurring in the sky every day. One in 10 of these are as bright as FRB 150807,” said Dr. Ravi, first author of a paper published recently in the journal Science.
“FRBs are extremely short but intense pulses of radio waves, each only lasting about a millisecond. Some are discovered by accident and no two bursts look the same,” Dr. Shannon added.
“FRB 150807 is the first detected to date to contain detailed information about the cosmic web — regarded as the fabric of the Universe — but it is also unique because its travel path can be reconstructed to a precise line of sight and back to an area of space about a billion light years away that contains only a small number of possible home galaxies.”
The astronomers observed FRB 150807 while monitoring a nearby pulsar in our Galaxy using the Parkes radio telescope in Australia.
They leveraged the brightness of the flash, and the fact that it was observed by two of their detectors simultaneously, to more accurately pinpoint where it may have occurred.
These measurements narrowed down the flash to several possible sites, with the most likely one being a galaxy called VHS7.
FRB 150807 appears to only be weakly distorted by material within its host galaxy, which shows that the intergalactic medium in this direction is no more turbulent than theorists originally predicted. This is the first direct insight into turbulence in intergalactic medium.
“Because FRBs like the one we discovered occur billions of light-years away, they help us study the Universe between us and them,” Dr. Ravi said.
“Nearly half of all visible matter is thought to be thinly spread throughout intergalactic space. Although this matter is not normally visible to telescopes, it can be studied using FRBs.”
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V. Ravi et al. The magnetic field and turbulence of the cosmic web measured using a brilliant fast radio burst. Science, published online November 17, 2016; doi: 10.1126/science.aaf6807
