Cosmic Violence

By cjohnson | September 12, 2005 9:52 pm

The Swift space telescope (links here and here) (along with a collection of ground-based telescopes) has set a new record for the furthest seen Gamma Ray Burst event. There’s a BBC news story on it here*

These objects are among the most truly spectacular (and puzzling) events in astronomy.

Here are some quotes:

Gamma-ray bursts are intense flares of high-energy radiation that appear without warning from across the cosmos.

They can release as much energy in a few minutes as our Sun will emit in its expected 10-billion-year lifetime.

Here is a nice site about Gamma Ray Bursts, with some history and a bit more of the science.

GRBs are generated by violent events, expected to be processes such as stars collasping, perhaps forming a black hole. Another violent scenario involves to compact objects (neutron stars) merging into each other in tiny fractions of a second. Here is a site with some movies of simluations of such an event.

Here (from the BBC article) are the numbers for the new event:

The latest, record gamma-ray burst was detected on 4 September, 2005, and lasted about three minutes. It probably marked the death of a massive star as it collapsed into a black hole.

It has a so-called redshift of 6.29, which translates to a distance of about 13 billion light-years from Earth.

…and for real excitement, you can read the scientists’ chatter and some of the raw reporting of the data at the NASA site.


(*Thanks Fyodor!)

  • Moshe Rozali

    Clifford (or anyone else)

    Are those events important somewhere in cosmology (rather than just astrophysics), being bright and far one may think so…

  • Clifford

    Hi Moshe!

    I wondered about this too, but my understanding is that they’ll only tell you interesting stuff as far back as the era that the objects that give rise to them (massive stars) first arose. But I thought that was a bit late, compared to the “interesting” early cosmological eras, but there may well be interesting cosmology questions I know little about that do pertain to such later eras.

    There is some chatter about cosmology in the BBC article, but I’m not really convinced. I bet Risa knows a lot about this….. I know nothing and so will shut up now!


  • Risa

    Goodness gracious, Clifford — what tiny fraction of the history of the Universe do you consider “interesting”?!? ๐Ÿ˜‰

    From the little I’ve read, this event took place above redshift 6, which makes it one of the earliest observable things light sources in the universe (there are now just a handful of galaxies and quasars above z=6). I don’t know the specifics of these new data, or a ton about GRB physics, but even the existance of this event at this redshift tells us probably constrains the formation of the earliest stars in the Universe. Even if all you care about is the 5-10 magic cosmological parameters, and not the evolution of all of the light in the Universe, learning about early star formation can help constrain the reionization era — which is degenerate with a lot of those parameters.

  • Clifford

    Told you I know nothing!… ๐Ÿ˜€


  • Moshe Rozali

    Thanks Risa. I guess there could be a question what I meant by cosmology, just meant “large scale structure of the universe” (which is of course a book about something else), and by large I would include galaxies and above. There is also the sense of cosmology referring to scales in which the universe is homogeneous and isotropic, as in the cosmological standard model . Maybe there should be separate terms for both ( I vote for “5-10 magic numbers” for the latter).

    Anyhow, I seem to remember early reionization was also in the CMB cards, so I guess my two data points are consistent…



  • Risa

    Cosmology for the former and “5-10 magic numbers” for the later sounds good to me — I work mostly on large scale-structure and galaxy formation (and sometimes on figuring out said numbers), and I definitely consider myself to be a cosmologist! I just thought Clifford’s “interesting” was neglecting essentially everything after first light… always funny to hear 13.5 billion years ago referred to as “later times” ๐Ÿ˜‰ But I know even less about string theory, so I’ll give you a break now, Clifford.

    Re early reionization, the first WMAP results indicated z_reionization around 17 (with a *huge* errror bar, which will hopefully go way down with the release of the second third year data) or so, but SDSS quasars now are showing that it seems to be pretty patchy (varies between lines of sight to different quasars) and that it extends in some regions to about z~6 (perhaps later than these GRBs).

  • Clifford

    No… don’t give me a break. I sort of get into the bad habit of thinking of those 13.5 billion years as astrophysics (which is not to devalue it in any way), and push the term “cosmology” back earlier and earlier in the universe’s life… I shouldn’t. It’s wrong. Bad me.



  • Mark

    Cosmic acceleration is a cosmological phenomenon of central importance, tied to fundamental physics in a deep way and effective at (and discovered by looking at objects that are at) redshifts less than 2.

  • Adam

    I’d have thought that anything distant is useful because it helps fill in the gaps in structure evolution between decoupling (where the state of the universe is imprinted in the CMB) and the structure that we see today. Anything to help fill in those gaps is necessarily going to be bright, I’d have thought.

  • Adam

    I should add that I’m no cosmologist, although I do know one or two.

  • Arun

    Does the very fact of observability of gamma ray bursts from so far away put any interesting constraints on what might lie between the gamma ray burster and us?

  • Adam

    Would that not require a better understanding of what the GRB actually is, ie, you’d have to know what to expect from the emissions to judge how they’d been affected by the intervening space and its contents?

  • Tim D

    Hi all,

    There are tons of interesting cosmological applications of GRBs. Some of them aren’t quite ready for prime-time, but give us a few years (and a larger dataset) and I bet we can compete! Like Risa said, GRBs are great for studying “later times” cosmology (reionization, first stars, etc), but they also might have something to say about the “5-10 magic numbers”.

    In a lot of ways, GRBs are the ideal probe of the reionization epoch in that they are easy to find and some percentage are likely occur and are detectable out to redshifts of 10-20. Check out Lamb & Reichart for a review of the cosmological applications. GRBs are nicer than quasars for measuring the Gunn-Petersen trough because they have a simple intrinsic spectrum and, being transient events, they haven’t completely disrupted the local environment before they explode (no proximity effect). People do want to use them analogously to quasar absorption systems to put constraints on what lies between the burst and us (like Arun suggested). The challenge is ensuring that the afterglow be detected and that high-resolution spectra of the afterglow can be obtained fairly quickly using the new generation of NIR spectrometers. Hopefully, this latest Swift burst is just the tip of the iceberg in this regard.

    Probably the cosmology result that’s generating the most excitement right now is the use of GRBs as “standardizable candles” much in the same way that Type Ia supernovae have been used. The breakthrough came last year in a paper by Ghirlanda, Ghisselini & Lazzati, where they discovered a very tight correlation between the total energy emitted in gamma-rays and the peak of the prompt spectrum. Using this correlation they can place GRBs on Hubble diagrams, and they claim that a future large sample of Swift bursts will be competitive with the supernovae results in constraining OmegaM, Omega_Lambda and w.

  • Clifford

    “Probably the cosmology result that’s generating the most excitement right now is the use of GRBs as “standardizable candles” ”

    Tim D: That is a really exciting prospect! Has there been followup work on that?


  • Brad Holden

    There are a number of projects going on right now to use GRBs as standard candles. All of the big telescopes have programs to interrupt regular observations to take spectra of GRBs, to measure their redshifts, and there are dedicated telescopes for getting their light curves. Hopefully in a year or so, these results will pan out, though probably not at the redshifts Tim D is interested in, if he wants to use NIR spectrographs.

    To me, the most exciting near term results will be using GRBs to study the intergalactic medium. There is already a great spectrum out there in astro-ph/0508270 from a GRB. The really cool thing is it shows stuff that no one has ever seen before. Frankly, the authors cannot make heads or tails of some of the features, that is just awesome.

  • Moshe Rozali

    Wonderful, this is the kind of thing I was fishing for…what can I say, the blog as an educational tool…

  • Tim D

    Hi Clifford,

    Yep, it is quite exciting. The results in the Ghirlanda et al. paper I referenced are pretty much the state-of-the-art right now. There are several other groups working along the same lines, but since everyone is using the same catalog of 40 or so bursts they’re getting similar answers. If we could increase the size of the sample of usable bursts then we could (1) test that the correlation is indeed correct, and (2) shrink the confidence regions for the cosmological parameters.

    For a burst to be useful in this project we need 3 quantities:

    (1) Burst redshift.
    (2) A well-measured afterglow light-curve, which gives us information about the opening-angle of the relativistic jet that causes the GRB, and hence information about its total energy budget.
    (3) A measurement of the peak energy of its spectrum.

    The Swift satellite is ideally suited to get (1) and (2) and should discover hundreds of bursts over the next few years. But Swift has a narrow spectral bandpass and has a hard time measuring (3). The HETE-2 satellite has a much broader spectral bandpass and can easily measure (3) for a wide range of bursts. So a collaboration between Swift and HETE-2 would greatly expand this dataset. Hopefully these arguments will convince NASA to fund HETE-2 in the coming years (full disclosure: I currently work on the HETE team :-)

    In particular, HETE-2 is particularly adept at detecting the low-energy cousins of GRBs — X-Ray Flashes. XRFs seem to follow this same correlation as GRBs, but are usually seen at lower redshifts. And as Mark pointed out above, having probes of the z

  • Tim D

    (oops, looks like the end of my last comment got munched. Here’s the rest…)

    In particular, HETE-2 is particularly adept at detecting the low-energy cousins of GRBs รขโ‚ฌ” X-Ray Flashes. XRFs seem to follow this same correlation as GRBs, but are usually seen at lower redshifts. And as Mark pointed out above, having probes of the z less than 2 universe is key to understanding Dark Energy. GRBs are special because they may be standardizable candles that are visible over a redshift range of 0.1 to 6.3 (and possibly higher).

    The correlation uncovered by Ghirlanda et al. is also a challenge for theorists to explain. A better understanding of the underlying physics of the GRBs will hopefully allow us to understand and better use these correlations, and thereby improve the cosmological results as well.

  • Plato

    We would like to stress that in order to use GRBs to find the cosmological parameters, we need a set of well measured data, and especially a well measured jet break time tbreak, necessary to find the collimation angle , and a good spectral determination of the prompt emission.

    Would “Glast” determinations fit into this category?

  • Tim D

    “Would “Glast” determinations fit into this category?”

    I’m not too familiar with the proposed GLAST instrument so someone correct me if I’m wrong, but from what I can tell from their public website they are looking at much higher energies (0.01-100 GeV) than Swift or HETE-2 (2-400 keV). In which case, they would also have a hard time getting spectra for all but the highest energy bursts. Of course, that range of parameter space may also be really interesting for other things.

  • Plato

    Of course, that range of parameter space may also be really interesting for other things

    Please excuse my layman views:)

    When I saw the issue of meauring the time valuation of events in our early cosmological history, how could it not be considered in high energy applications?

    I think this is the point about our depth of perception.

    The “calorimetric views” provide the consistancy and penetration of the cosmological events as tangible realities, in relation too, the expansion of our universe.

    Such depths require a consistant view. From the “planck epoch” to now?

    Such views are not understood if one did not have some comprehension of “the views” of that early universe. Andrey Kravtsov is very helpful here.:)

  • Plato

    Part of this image url can be broken down to “prospective site” for education. Atlas comes to mind.

    I hope this is correct?


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