Virgo-originating cosmic rays bend around in the galaxy’s twisting field lines so that they strike us from the direction of Canis Major, where Auger sees the center of its excess. The researchers analyzed how the resulting pattern would change for cosmic rays of different energies. They consistently found a close match with different subsets of Auger’s data.
The researchers’ “continuous model” of the origins of ultrahigh-energy cosmic rays is a simplification — every piece of matter does not emit ultrahigh-energy cosmic rays. But its striking success reveals that the actual sources of the rays are abundant and spread evenly throughout all matter, tracing the large-scale structure. The study, which will appear in The Astrophysical Journal Letters, has garnered widespread praise. “This is really a fantastic step,” Watson said.
Immediately, certain stocks have risen: in particular, three types of candidate objects that thread the needle of being relatively common in the cosmos yet potentially special enough to yield Oh-My-God particles.
In 2008, Farrar and a co-author proposed that cataclysms called tidal disruption events (TDEs) might be the source of ultrahigh-energy cosmic rays.
A TDE occurs when a star pulls an Icarus and gets too close to a supermassive black hole. The star’s front feels so much more gravity than its back that the star gets ripped to smithereens and swirls into the abyss. The swirling lasts about a year. While it lasts, two jets of material — the subatomic shreds of the disrupted star — shoot out from the black hole in opposite directions. Shock waves and magnetic fields in these beams might then conspire to accelerate nuclei to ultrahigh energies before slingshotting them into space.
Tidal disruption events occur roughly once every 100,000 years in every galaxy, which is the cosmological equivalent of happening everywhere all the time. Since galaxies trace the matter distribution, TDEs could explain the success of Ding, Globus and Farrar’s continuous model.
Moreover, the relatively brief flash of a TDE solves other puzzles. By the time a TDE’s cosmic ray reaches us, the TDE will have been dark for thousands of years. Other cosmic rays from the same TDE might take separate bent paths; some might not arrive for centuries. The transient nature of a TDE could explain why there seems to be so little pattern to cosmic rays’ arrival directions, with no strong correlations with the positions of known objects. “I’m inclined now to believe they are transients, mostly,” Farrar said of the rays’ origins.
The TDE hypothesis got another boost recently, from an observation reported in Nature Astronomy in February.
Robert Stein, one of the paper’s authors, was operating a telescope in California called the Zwicky Transient Factory in October 2019 when an alert came in from the IceCube neutrino observatory in Antarctica. IceCube had spotted a particularly energetic neutrino….
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