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A comment on What Is a Blazar? It’s Like Staring Down the Barrel of a Black Hole. Parent comment

Re:What Is a Blazar? It’s Like Staring Down the Barrel of a ... by SiempreViernes on Friday July 13, 2018 @06:09PM (#17527267)
Supposing it was astrophysical, the chance coincidence is low yes, but:

> The muon-neutrino astrophysical spectrum, together with simulated data, was used to calculate the probability that a neutrino at the observed track energy and zenith angle in IceCube is of astrophysical origin. This probability, the so-called signalness of the event (14), was reported to be 56.5% (17).

Meaning there is about even odds this was not from outer space, but from a cosmic ray hitting the atmosphere, and we know cosmic rays point back at nothing in particular.

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Re:What Is a Blazar? It’s Like Staring Down the Barrel of a ... by perl4ever on Friday July 13, 2018 @06:11PM (#17527293)
But does that probability take into account the coincidence of the putative source being lined up, or not?
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Re:What Is a Blazar? It’s Like Staring Down the Barrel of a ... by SiempreViernes on Friday July 13, 2018 @06:29PM (#17527422)
No, that is purely the chance that they correctly identified the event as being signal, it doesn't take into account known sources.

Given that the background is basically isotropic, I doubt adding in a source catalogue will move the probability much.

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Re:What Is a Blazar? It’s Like Staring Down the Barrel of a ... by perl4ever on Friday July 13, 2018 @09:23PM (#17528213)
You're saying there are blazars everywhere, such that no matter the trajectory, it would match to something? That doesn't sound right.
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Re:What Is a Blazar? It’s Like Staring Down the Barrel of a ... by SiempreViernes on Saturday July 14, 2018 @02:43PM (#17531691)
No, I'm saying cosmic rays come from anywhere (as the get deflected by magnetic fields) and when hitting the atmosphere they can create high energy neutrinos that can look like they are from space despite actually being from the atmosphere.
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