<p> Scientists have found that a radio emission believed to be an afterglow from a mysterious event called fast radio burst, actually originated from a supermassive black hole in the core of a distant galaxy.<br /><br /></p>.<p>Last year, researchers reported detecting the afterglow from a fast radio burst, which would pinpoint the precise position of the burst's origin, a longstanding goal in studies of these mysterious events.<br /><br />These findings were quickly called into question by follow-up observations.<br />"Part of the scientific process is investigating findings to see if they hold up. In this case, it looks like there's a more mundane explanation for the original radio observations," said Peter Williams, from Harvard University.<br /><br />As their name suggests, fast radio bursts (or FRBs) are brief yet powerful spurts of radio energy lasting only a few milliseconds. The first ones were only identified in 2007. Their source has remained a mystery.<br /><br />"We don't even know if they come from inside our galaxy or if they're extragalactic," said Edo Berger, from Harvard.<br /><br />Most FRBs have been identified in archival data, making immediate follow-up impossible. The new event, FRB 150418, is only the second one to be identified in real time.<br /><br />Radio observations reported in the journal Nature purportedly showed a fading radio afterglow associated with the FRB. That afterglow was used to link the FRB to a host galaxy located about 6 billion light-years from Earth.<br /><br />Williams and Berger studied the supposed host galaxy in detail using the US National Science Foundation's Jansky Very Large Array network of radio telescopes.<br /><br />If the initial observations had been an afterglow, it should have completely faded away. Instead researchers found a persistent radio source whose strength varied randomly by a factor of three, often reaching levels that matched the initial brightness of the claimed afterglow.<br /><br />The initial study also saw this source, but unluckily missed any rebrightenings.<br />"The radio emission from this source goes up and down, but it never goes away. That means it can't be associated with the fast radio burst," said Berger.<br /><br />The emission instead originates from an active galactic nucleus that is powered by a supermassive black hole. Dual jets blast outward from the black hole, and complex physical processes within those jets create a constant source of radio waves.<br /><br />The variations we see from Earth may be due to a process called "scintillation," where interstellar gases make an intrinsically steady radio beacon appear to flicker, just like Earth's atmosphere makes light from stars twinkle.<br /><br />The source itself might also be varying as the active galactic nucleus periodically gulps a little more matter and flares in brightness.<br />The study appears in the Astrophysical Journal Letters.</p>
<p> Scientists have found that a radio emission believed to be an afterglow from a mysterious event called fast radio burst, actually originated from a supermassive black hole in the core of a distant galaxy.<br /><br /></p>.<p>Last year, researchers reported detecting the afterglow from a fast radio burst, which would pinpoint the precise position of the burst's origin, a longstanding goal in studies of these mysterious events.<br /><br />These findings were quickly called into question by follow-up observations.<br />"Part of the scientific process is investigating findings to see if they hold up. In this case, it looks like there's a more mundane explanation for the original radio observations," said Peter Williams, from Harvard University.<br /><br />As their name suggests, fast radio bursts (or FRBs) are brief yet powerful spurts of radio energy lasting only a few milliseconds. The first ones were only identified in 2007. Their source has remained a mystery.<br /><br />"We don't even know if they come from inside our galaxy or if they're extragalactic," said Edo Berger, from Harvard.<br /><br />Most FRBs have been identified in archival data, making immediate follow-up impossible. The new event, FRB 150418, is only the second one to be identified in real time.<br /><br />Radio observations reported in the journal Nature purportedly showed a fading radio afterglow associated with the FRB. That afterglow was used to link the FRB to a host galaxy located about 6 billion light-years from Earth.<br /><br />Williams and Berger studied the supposed host galaxy in detail using the US National Science Foundation's Jansky Very Large Array network of radio telescopes.<br /><br />If the initial observations had been an afterglow, it should have completely faded away. Instead researchers found a persistent radio source whose strength varied randomly by a factor of three, often reaching levels that matched the initial brightness of the claimed afterglow.<br /><br />The initial study also saw this source, but unluckily missed any rebrightenings.<br />"The radio emission from this source goes up and down, but it never goes away. That means it can't be associated with the fast radio burst," said Berger.<br /><br />The emission instead originates from an active galactic nucleus that is powered by a supermassive black hole. Dual jets blast outward from the black hole, and complex physical processes within those jets create a constant source of radio waves.<br /><br />The variations we see from Earth may be due to a process called "scintillation," where interstellar gases make an intrinsically steady radio beacon appear to flicker, just like Earth's atmosphere makes light from stars twinkle.<br /><br />The source itself might also be varying as the active galactic nucleus periodically gulps a little more matter and flares in brightness.<br />The study appears in the Astrophysical Journal Letters.</p>