Hoped-for clue to FRB origin may have been signs of a snacking black hole instead, study claims
MIXED SIGNALS Radio telescopes at the Very Large Array (shown) picked up more emissions from the alleged host galaxy of a cosmic radio burst, calling into question claims of the signal’s origin.
A recently claimed home for an elusive cosmic radio burst might not be the host galaxy after all. What appeared to be an afterglow from the eruption might instead have been a run-of-the-mill radio emission from an unrelated galaxy, researchers claim online February 28 at arXiv.org.
Fast radio bursts, ephemeral blasts of radio waves that appear to originate in other galaxies, have been stumping astronomers since 2007 (SN: 8/9/14, p. 22). Identifying a host galaxy for an FRB could provide a clue to its cause. A recent FRB seemed to finally leave a return address (SN Online: 2/24/16). Two hours after the initial detection, astronomers caught a fading radio signal coming from the same direction. That signal led a team headed by Evan Keane, an astronomer with the Square Kilometer Array Organization in Macclesfield, England, to a galaxy about 6 billion light-years away.
But the claimed afterglow might have nothing to do with the FRB, Harvard University astronomers Peter Williams and Edo Berger suggest. A supermassive black hole appears to live in that galaxy, and it is actively feeding off a swirling disk of interstellar detritus. Such cosmic snacks routinely belch out radio waves. Observations of the galaxy obtained on February 26 and 27 at the Very Large Array in New Mexico show that not only has the “afterglow” returned, but it is brighter than what researchers saw in the hours after the FRB detection.
Williams and Berger argue that the galaxy is not the home of the FRB. But Duncan Lorimer, an astrophysicist at West Virginia University in Morgantown, says “I would be cautious about dismissing the result.” Astronomers don’t know what causes FRBs and many mysteries remain. One burst detected in 2012, for example, recently became the first FRB known to repeat itself after erupting 10 more times last year (SN Online: 3/2/16). It’s possible that this one repeats as well, Lorimer says. “It tells us how little we still know.”
Keane and colleagues are performing additional studies to better understand what’s going on. “When we've completed and fully considered those, we will certainly report our findings,” he says. “I know that FRBs are exciting, and appreciate that there is a lot interest, but we really can't rush the scientific process.”
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