More mysterious extragalactic signals detected



Just in time for the holiday shopping season, astronomers snagged a two-for-one deal on mysterious blasts of radio waves from other galaxies. An unprecedented double burst recently showed up along with four more of these flashes, researchers report online November 25 at arXiv.org.
Fast radio bursts, first detected in 2007, are bright blasts of radio energy that last for just a few milliseconds and are never seen again (SN: 8/9/14, p. 22). Until now, astronomers had cataloged nine bursts that appeared to originate well outside the Milky Way. Yet, follow-up searches with nonradio telescopes for anything that might be pulsing or exploding keep coming up empty (SN Online: 12/8/14).
The five newcomers, detected at the Parkes radio telescope in Australia, follow the same pattern as all previous detected bursts with one exception — one flashed twice. Twin blasts separated by just 2.4 milliseconds came out of some sort of eruption that happened roughly 9 billion years ago in the constellation Octans, David Champion, an astronomer at the Max Planck Institute for Radio Astronomy in Bonn, Germany, and colleagues report.
A double flash rules out some ideas about what causes fast radio bursts. For instance, two neutron stars, dense cores left behind by dead massive stars, can collide only once. Rare vigorous blasts from pulsars might fit the bill, as would hyperflares from haphazard sources of gamma rays and X-rays known as “soft gamma repeaters,” possibly triggered by starquakes on highly magnetic neutron stars. 
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