The true nature of the mysterious fast radio bursts (PRB) may not have been finally revealed.
These energetic flashes seem to appear in random places in space, and they appear and disappear within a few milliseconds, which makes them extremely difficult to identify. Until February, only a few confirmed by the FBI signals were recorded in archival radio astronomy data. Since these signals were recorded several months or years ago, subsequent follow-up observations were impossible, with the result that the source of these flashes was steeped in mystery.
But that was until the Australian 64-meter telescope Parkes Radio was not lucky to notice the outbreak of the FRB. Immediately, the international collaboration of astronomers was notified of this, and the other observatories turned in the direction of the flash, to study its radio afterglow. The Japanese Subaru telescope on Mauna Kea in Hawaii could aim at the flash point and determine the source galaxy.
Very quickly, the collaboration drew some conclusions based on the information they gathered from the source. The galaxy was old and lies about 6 billion light-years from Earth. This galaxy has few signs of star formation, so it was clear that the FBI (at least in this isolated case) was probably not associated with star formation processes. The FRB signal, known as the FRB 150418, was even used to test some of our space models — by analyzing the signal and, knowing where it happened, some of the astrophysicists were able to measure the cosmic expansion and the amount of dark matter through which the radio emission passed.
Although great hopes were pinned on the events of February, which were evidence of a new cosmic phenomenon, problems quickly surfaced for the astronomical community: Was the FBI 150,418 really the FBI? Or is this famous phenomenon under the guise of a mysterious impulse?
In a new study, accepted for publication in the Astrophysical Journal Letters, Harvard astronomers Peter Williams and Edo Berger suggest that this particular signal was in fact a randomly erroneous identification and the real source of the FRB remains a mystery.
Using the installation of the American Science Foundation Jansky Very Large Array in New Mexico, Williams and Berger collected radio data from a suspicious galaxy, which produced the FBI 150418, and found even large radio pulses. FBIs are believed to be single flashes; they blink, producing a huge output of energy within a few milliseconds, and then disappear. This galaxy, however, still generates bursts of radio emission, some as powerful as the measured afterglow of the FBI 150418.
“There’s nothing unusual in what the other team saw,” said Berger in a statement. "The radio emission from this source goes up and down, but it never goes away. This means that it cannot be associated with a fast radio burst." So what could be causing this signal? Well, supermassive black holes in the centers of active galactic nuclei constantly pulsate with the emission of radio emission. Matter inside the galaxy bulge, such as stars, dust and gas, falls into the trap of the gravitational well of a black hole, forming an accretionary hot disk. In addition, huge black holes constantly flash with the emission of powerful jets of relativistic matter ejected from the poles of a black hole. Thus, a lot of radio waves are created.
Over the vast distance between this galaxy and the Earth, interstellar gases cause the glow of radio waves - in other words, a steady radio signal from afar will seem to flicker. And this is probably what was discovered in February: a flickering radio signal from a supermassive black hole, and not the FRB.
So it seems that the mystery of the origin of the FBI remains as mysterious as it was in 2007, when the first FBI signals were found in the archival data. “We don’t even know if they originate from our galaxy or they are extragalactic,” said Berger, pointing out that we are currently attacking a puzzle track as strange as gamma-ray bursts 30 years ago.