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What is frequency of a gamma ray emitted from a supernova

  1. Jun 10, 2009 #1
    From what i have read the gamma ray frequency cap ranges from 3×10^19 to 3×10^24. I wanna know what you guys have heard it is. Are the highest measured gamma ray from a supernova calculated with any time dialated effects? Also what is the thoertical cap of something higher than a gamma ray, what i mean are there any theories saying the limit to the energy a photon can have will be greater if something smaller than a photon is emitted (or thought to possibly exist with an explosion of that size)?

    P.S. I know of wikipedia so citing it isnt very helpful, please try to refrain.
     
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  3. Jun 10, 2009 #2

    Chronos

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    Time dilation effects are strictly a function of distance - i.e., the hubble flow. There is no intrinsic gravitational time dilation from the star itself.
     
  4. Jun 12, 2009 #3
    Are you positive, I thought the slowing of time within a gravitatinal field would also cause redshift, possibly only nanoseconds from a star. Gravitational time dialation I think is proven by GR. Now i was given an equation to calculate gravitational time dialation by another PF member. Are you referring to merely with stars theselves? Or are you saying all gravitational time dialation is non-existant.
     
  5. Jun 19, 2009 #4
    I hadn't heard of a frequency ceiling for gamma-rays. Where did you hear of it?
     
  6. Jun 19, 2009 #5

    Wallace

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    Hi downlow. There is no fundamental limit to the frequency a photon can have, so as qraal suggested if you give us your source it might help you get a better answer.

    I'm speculating, but what you could be referring to is the Greisen–Zatsepin–Kuzmin limit (commonly just the GZK limit) that postulates a limit to the cosmic ray energy, as seen in particles striking the Earth's atmosphere. Note that cosmic rays are not photons (and hence not gamma rays) but are in fact very fast moving particles such as protons or other small nuclei. The origin of this limit is due to the cosmic microwave background. Cosmic rays above the limiting energy would interact with CMB photons producing multiple lower energy particles ( I can't remember the exact mechanism at play). This continues until the cosmic ray is below the threshold for this type of interaction.

    Strictly speaking, this limit applies only to cosmic rays travelling distances much greater than the size of our galaxy, meaning that we could see cosmic rays over this limit if there was a source strong enough within our own galaxy. We think that the very highest energy cosmic rays are produced in Active Galactic Nuclei (which our galaxy does not currently have) and so if we did see cosmic rays above this limit it would be interesting; either there is some stellar sized source capable of making such high energy particles, or for some reason high energy particles can travel long distances. To date not conclusive observations of particles above this limit have been made, although there has been some controversy around the question.

    Note that
    is not very helpful. Time dilation can occur for any number of reasons, including in intrinsic effect due to photons climbing out of the gravitational potential of the star or whatever else is emmitting a photon. When trying to work out the energies that particles have when emmitted from various astrophysical events in principle this instrinsic effect needs to be taken into account. In practice how important that is in comparison to cosmological effects will depend on the nature of the event and the distance from us that it occured. I'm not sure in practice how important this is for Supernovae, but certainly the gravitationl time dilation is observed in the observations of AGN.
     
  7. Jun 20, 2009 #6

    Chronos

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    I am not aware of any compelling evidence suggesting intrinsic time dilation in supernova studies, Wallace. Please provide references.
     
    Last edited: Jun 20, 2009
  8. Jun 20, 2009 #7

    Wallace

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    Chronos, I as said, there will always be time dilation due to the gravitational potential of the object itself. How important that is in understanding a particular event depends on the object and the size of any other effects (such as cosmological). Again, to repeat myself, I'm not sure in practice how important that is for different SN types, and whether they are in our galaxy or at cosmological distances. But no, your right, we shouldn't worry about actually explaining anything to people. We should just make one sentence posts out of context of the thread and demand anyone giving a fuller explanation 'provide references'.:rolleyes:
     
  9. Jun 24, 2009 #8

    Chronos

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    We should explain everything, in clear terms, Wallace, that is the only thing I insist upon. We are not disagreeing upon anything in principle.
     
  10. Jun 25, 2009 #9

    Chronos

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  11. Jul 3, 2009 #10
    d0wnl0w : I must apologize, for not keeping the information I recieved about this subject, so I can only tell you it is out there. One observation made by the University of Texas sited an unusual observation of receiving two distinct frequencies of gamma radiation from a super nova, I think the time span would put it close to July 2008. However I would say the period of a photon in wave length can not be less than Planck Length, this I derive from logic. This is a very important detail in both quantum physics and relativity. However this does not limit the relativistic mass of the quanta, only the disturbance by the relativistic mass known as an electromagnetic wave.
     
    Last edited: Jul 3, 2009
  12. Jul 3, 2009 #11

    marcus

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    I assume you mean Hz
    and the frequency "cap" you say you read about corresponds to 12 GeV.

    That's fairly commonly observed, I believe. One hears often of 10 GeV photons observed in GRB (gammaray bursts).

    And GRB are commonly assumed to be produced by supernovae.

    The gamma photons would not necessarily be produced near the collapsing star so the star's gravity might not factor into it in a very clean crisp way. They might be produced far out along the polar jet of relativistic charge particles.

    But you are asking a worthwhile question. Better put it in GeV terms, not frequency, since GeV is a more common way to talk about gamma photons.

    You are asking about the "cap" on GeV of GRB photons. What is a good rough estimate of the "cap"?

    We know that AGN blazar flare photons are observed at TeV. They can arrive to earth atmosphere with several TeV energy. But that is not a supernova GRB.
    We know that 10 GeV and stuff on the order of 10 GeV is common enough. So where in this huge range say between 10-100 GeV would we find this elusive "cap"?

    I'm trying to clarify the question because I think it is a good one and I'd like to know the answer. I didn't know of any sharp physical limit. Maybe someone will illuminate this for us.
     
  13. Jul 3, 2009 #12
    A side question: what's the highest energy gamma-rays observed?
     
  14. Jul 3, 2009 #13

    marcus

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    At least one or two TeV, for example by the IACT telescope in the Canary Islands (imaging air cherenkov telescope)
    This site has some pictures. I cant tell you the top limit, only a smattering of what they reported so far.
    http://wwwmagic.mppmu.mpg.de/
    If you look here at a summary of results
    http://magic.mpp.mpg.de/physics/recent/recent_results.html [Broken]
    you will see figures of a few TeV, and they also give links to the technical journal papers where they published the results.
    At one place on that page they mention 9 TeV but I didn't check to make sure. You have to evaluate.

    I don't know if other instruments have seen anything significantly higher energy. I only have sketchy knowledge in this area and am merely telling you what I happen to know about.

    There is a review article by Floyd Stecker but it's old. If someone has a lead on some recent review paper please share.
     
    Last edited by a moderator: May 4, 2017
  15. Jul 3, 2009 #14
    Highest secure claim I am aware of is 20 Tev, detected by HESS from LS5039 reported in Astro-ph/0607192. LS5039 is a High Mass X-Ray Binary.

    Best,
    Jim Graber
     
  16. Jul 4, 2009 #15

    marcus

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    Bravo Jim! thank you. I believe HESS is also a IACT (imaging atmospheric cherenkov telescope) like the Canary Island one called "Magic" that I was talking about. It's a neat technology. You have an optical telescope that looks up into the atmosphere some 20 kilometers high and looks for blue/UV tracks. A photon comes in and socks it to a shower of particles and some are going faster than the speed of light in air, so they radiate Cherenkov light. And from the size of the trail you can tell the energy of the incoming photon. From the image of the trail you can tell where in the sky it came from. So a 10 km thick layer of atmosphere is your particle detector. Correct me please on any detail I've got wrong.

    As I recall the Magic dish is some 17 meters diam. What about Hess?
    http://en.wikipedia.org/wiki/MAGIC_(telescope)
     
    Last edited: Jul 4, 2009
  17. Jul 4, 2009 #16
    To my understanding the absolute maximum relativistic mass of an electromagnetic quanta is 2.73x10^-8 kg or 1.39x10^16Tev if this is any help.
     
  18. Jul 4, 2009 #17

    Vanadium 50

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    This is not correct.

    The energy of a photon is a frame dependent quantity, so there is no "absolute maximum". For any energy, one could describe the event using a coordinate system where that energy is larger.
     
  19. Jul 4, 2009 #18
    Vanadium 50 : Thank you for your information. Yes I agree from that stand point.
     
    Last edited: Jul 5, 2009
  20. Jul 5, 2009 #19
    http://www.mpi-hd.mpg.de/hfm/HESS/pages/about/telescopes/
    Here is a link to their home page. Hess has four telescopes about the same size as MAGIC.
    HESS is in southern Africa in Namibia.
    Jim Graber
     
  21. Jul 5, 2009 #20
    More on extreme energy gamma rays

    If you look at log plots of spectra from HESS, there are points at 30 TeV for the Crab and for MGRO J1908+6. This implies they’ve seen more than one photon at or near that energy. As gamma rays get more and more energetic, it gets harder and harder to tell them from cosmic rays, which are believed to be massive particles (probably mostly protons, but possibly also iron nuclei etc.). The most powerful cosmic ray detected was of order 3X 10^20 eV ie 300EeV, about seven orders of magnitude greater than the 20 or 30 TeV 3X 10^13 eV photons with a known source mentioned above.
    The Pierre Auger Cosmic Ray telescope sees eight suspicious events above an EeV that look like photons. However, the experts consider that these eight events are probably not extreme gamma rays, but rather that they are unusual cosmic rays. You can read all about it at this link.
    http://arxiv.org/abs/0903.1127

    Still it is true that the upper energy limit of observed gamma rays is very uncertain by many orders of magnitude.
    Best,
    Jim Graber
     
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