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Photons - most energetic ever detected

  1. Dec 21, 2008 #1
    Does anyone know how energetic the most energetic photons ever detected from a natural source were and what their source was?
  2. jcsd
  3. Dec 21, 2008 #2
  4. Dec 21, 2008 #3
    Check out this link to a paper that discusses the Pierre Auger Observatory searching for UHE photons. They discuss detecting photon events at about 2.2 EeV. (1 EeV = 10^18 eV).

    Here is the link: http://www.auger.org/technical_info/pdfs/icrc2007/icrc602.pdf

    I do not know if these are the most energetic photons detected or not.
  5. Dec 21, 2008 #4
    I would have to question your interpretation of this very interesting article you cited. In citing the figure 2.2 EeV, I think you must be referring to Figure 3 therein, but the scale there is Log(Energy/EeV) - not Energy/EeV and the anti-Log of 2.2 would give an energy of about 158 EeV for the most energetic photons that this work detected. This is same order of magnitude as the energy of the 300 EeV Oh-My-God particle detected on October 15, 1991, over Dugway Proving Grounds, Utah - and 15 similar events detected since. So, considering that the text of the paper paper is focused on photons with energies above 10, 20 and 40 EeV, I think they obviously detected photons much more energetic than 2.2 EeV.
  6. Dec 21, 2008 #5
    Ah, yes. Rightfully so. Sorry was a quick glance after searching the Auger site for photon articles. I had a recent discussion with one of the Auger scientists, so I checked their site first.

    And correct me if I am wrong, but wasn't the 1991 event thought to be a charged particle? I understand particle identification at these energies is very difficult, but I seem to remember that at the time (and as recently as a few years ago when I heard some talks from the Fly's Eye collab.) that they were thinking it was a positively charged particle.
  7. Dec 21, 2008 #6
    Yes, that is my understanding. See the link given by Dimitry67 in the first reply to this thread. That was the source of my information about the Oh-My-God particle. I didn't mean to imply that it was a photon - merely that the energy of the most energetic photons observed in your citation was comparable.
  8. Oct 29, 2010 #7
    I think the results of Pierre Auger are misinterpreted here. If you look at Figure 4 of the cited paper, the result of search is only an upper limit on the photon flux. The conslusion of the paper is strong limit on the photon flux with 0 photon candidate events (as stated in conclusion). Presently no photons with energies >~1 EeV are observed in any of the experiments (all detected particles of these energies are assummed to be protons or nuclei). Therefore the highest energetic photons come from gamma-astronomy and have energy of the order of hundreds TeV.
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