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Thread: GRB 130427A - burst of the (quarter) century

  1. #31
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    Very likely just a coincidence. The first three months of this year were very sparse in terms of GRBs, and then April and now May are very good.

    I always joke that another round of funding talks must be coming up for Swift ...

    But here's at least a moderate reason for more GRBs and better detections, at least from Swift's side: One of the big issues right now in astrophysics is the approach of gas cloud G2 toward the supermassive black hole near the Galactic center. Swift has been doing a lot of GC coverage in recent months. This means it stares for a lot of time at the same spot. Even if it catches a GRB, it will be behind the Galactic bulge, and basically lost to optical astronomy.

    Starting especially with GRB 130418A, Swift has been spending more time following up the X-ray afterglows of GRBs. This means it slews more across the entire sky, enhancing the chances of catching a GRB, and especially catching one that is well-observable, far off the Galactic plane. For example, the sky position of the new bright GRB 130505A is really close (relative to the complete sky) to GRB 130427A, I'd quite sure Swift was observing the afterglow of 27A when this new one went off at the edge of the BAT FoV.

  2. #32
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    Quote Originally Posted by Don Alexander View Post
    ... here's at least a moderate reason for more GRBs and better detections, at least from Swift's side: One of the big issues right now in astrophysics is the approach of gas cloud G2 toward the supermassive black hole near the Galactic center. Swift has been doing a lot of GC coverage in recent months. This means it stares for a lot of time at the same spot. Even if it catches a GRB, it will be behind the Galactic bulge, and basically lost to optical astronomy. ...
    OK, that's a pretty cool reason. I've been paying attention to the G2 story, but didn't realize that Swift was on the job to this degree.
    Forming opinions as we speak

  3. #33
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    Quote Originally Posted by Don Alexander View Post
    Swift has been doing a lot of GC coverage in recent months. This means it stares for a lot of time at the same spot.
    Yeah, that sounds like our Swift!
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  4. #34
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    Oh, and we just now got a report of YET ANOTHER LAT detected GRB, GRB 130504C!!!

    http://www.isdc.unige.ch/integral/ib...02-39824-0.png

    While it has an 0.15 degree LAT localization, it's hardly observable from the ground, and additionally is behind quite a bit of extinction. So another one that will likely not amount to much.

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    .... and the Konus-Wind observations of GRB 130505A are out, and it is officially the most energetic GRB (isotropically!) known!!!

    As shown by a certain D. A. Kann and his colleague S. Schulze, don't know if they can be trusted, sounds shifty.

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    Quote Originally Posted by Don Alexander View Post
    .... and the Konus-Wind observations of GRB 130505A are out, and it is officially the most energetic GRB (isotropically!) known!!!

    As shown by a certain D. A. Kann and his colleague S. Schulze, don't know if they can be trusted, sounds shifty.
    Congratulations! So is it time to break out the bubbly or is this just another (Sun-)day at the office?

  7. #37
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    Quote Originally Posted by slang View Post
    Originally Posted by Don Alexander
    Swift has been doing a lot of GC coverage in recent months. This means it stares for a lot of time at the same spot.
    Yeah, that sounds like our Swift!
    Hey! I resemble that remark.

    On a different note, I wonder if the woowoos will latch onto this string of GRBs as a sign of something.
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  8. #38
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    Quote Originally Posted by glappkaeft View Post
    Congratulations! So is it time to break out the bubbly or is this just another (Sun-)day at the office?
    NO!

    It turns out the Konus-Wind team had a typo in their GCN (and the one for GRB 130427A)!! They gave values in the 20 - 10000 keV band, but stated "20 - 1200". We corrected for this "narrow" energy band, but obviously overcorrected.

    Retraction GCN will be issued shortly.

  9. #39
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    Quote Originally Posted by Swift View Post
    Hey! I resemble that remark.

    On a different note, I wonder if the woowoos will latch onto this string of GRBs as a sign of something.
    Alien civil war or Vacuum Metastability Event? Reminds me of a question I have... but I'll start a different thread for it.
    Et tu BAUT? Quantum mutatus ab illo.

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    I think grb 130505A has no existence in any Swift/Fermi database. And GRB 130327A has only 7*10^53 ergs of total and few 10^53 ergs of luminosity..No where near to 110918a. The thing that is confusing is that these are Isitropic calculations which all scientists say are exaggerations,coz the real energy/power output of the GRBs are measure after correcting them for collimation and doppler boosting of beamings. So when we take that into account are GRBs like 110918A and GRB 080916C still the most luminous and enegrtetic ones respectively? For 110918a no such correction has been performed like what has been done for 080319b . For 19b the true luminosity got lowered from 10^52 ergs to around 10^50 ergs. So the most LUMINOUS grbs seem to have powers al clustering around 10^43 watts..but only grb which seemed to have crossed the canonical 10^44 watts was GRB 090926A(as far as I can remeber). Grb 130427a was not a very exceptionally energetic one then..only bright because of its relatively low redshif like those grbs of '88. And can any non-lensed quasars intrinsically reach upto 10^42 watts which I read was the ballpark estimate for normal long grbs' power output?

  11. 2013-May-06, 07:01 AM
    Reason
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  12. 2013-May-06, 07:02 AM

    Reason
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  13. 2013-May-06, 07:04 AM
    Reason
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  14. #41
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    And one more question has any non-lensed quasar ever reached upto 10^42 watts of luminosity comparable to the corrected GRB power?

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    Only1Indrajit,

    I removed your duplicate posts. As a "newbie" your posts sit in a "moderation queue" to be approved before they become visible - it is part of our anti-spam measures. Please be patient, we'll get to them. A couple of more posts and this won't happen any more.
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  16. #43
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    Quote Originally Posted by Ara Pacis View Post
    Alien civil war or Vacuum Metastability Event? Reminds me of a question I have... but I'll start a different thread for it.
    The Q and the Grey.

  17. #44
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    Quote Originally Posted by Only1Indrajit View Post
    I think grb 130505A has no existence in any Swift/Fermi database.
    Excuse me? What are you talking about?
    BAT refined analysis page on GRB 130505A: http://gcn.gsfc.nasa.gov/gcn/notices_s/555163/BA/
    Jochen Greiner's page on GRB 130505A, collecting Swift data and GCNs: http://www.mpe.mpg.de/~jcg/grb130505A.html
    I wrote last page already that it was not detected by Fermi, likely due to simple Earth occultation.
    Quote Originally Posted by Only1Indrajit View Post
    And GRB 130327A has only 7*10^53 ergs of total and few 10^53 ergs of luminosity..No where near to 110918a.
    You say that like it's a bad thing... Not to mention I never claimed any such thing.
    Quote Originally Posted by Only1Indrajit View Post
    The thing that is confusing is that these are Isitropic calculations which all scientists say are exaggerations,coz the real energy/power output of the GRBs are measure after correcting them for collimation and doppler boosting of beamings.
    No one corrects for Doppler beaming. Also, correcting for collimation needs precise late-time afterglow data. Using and comparing isotropic energy releases is perfectly valid.
    Quote Originally Posted by Only1Indrajit View Post
    So when we take that into account are GRBs like 110918A and GRB 080916C still the most luminous and enegrtetic ones respectively? For 110918a no such correction has been performed like what has been done for 080319b . For 19b the true luminosity got lowered from 10^52 ergs to around 10^50 ergs. So the most LUMINOUS grbs seem to have powers al clustering around 10^43 watts..but only grb which seemed to have crossed the canonical 10^44 watts was GRB 090926A(as far as I can remeber).
    I assume you are referring to Brad Cenko's paper: http://iopscience.iop.org/0004-637X/732/1/29/
    All of these newer GRBs have not yet been studied in detail when it come to collimation correction. The X-ray afterglow of 130427A remains extremely bright, though, and has shown no signs of breaking into a steep decay.
    Quote Originally Posted by Only1Indrajit View Post
    Grb 130427a was not a very exceptionally energetic one then..
    Which I also never claimed. It's quite far up there, though. And far more energetic than any other GRB at a similar redshift.
    Quote Originally Posted by Only1Indrajit View Post
    only bright because of its relatively low redshif like those grbs of '88.
    Well, we don't know the redshifts of the three GRBs from the '80s, and likelsy never will. As I stated, there are indications of 830801B being extremely close (think z < 0.1). I have never seen the light curve of 840304. And 881024 was a very spipky GRB similar to 130427A, it could easily have been at z = 0.5 without breaking the mold.
    Quote Originally Posted by Only1Indrajit View Post
    And can any non-lensed quasars intrinsically reach upto 10^42 watts which I read was the ballpark estimate for normal long grbs' power output?
    This comparison begs a definition of spectral range in which to compare outputs. So far we have been talking hard X-rays/soft gamma-rays, and there, bright GRBs exceed the output of the entire universe for time periods of seconds. In terms of optical luminosity. GRB afterglows and typical quasars are comparable when the afterglow is roughly 12 hours old in the res-frame (of course, both luminosities span wide ranges). Generally, I'd say, no, not at all. Of course, quasars over long time spans emit way more energies than GRBs.

  18. #45
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    GRB 130427A has made it to the popular media.

    CNN.com
    On April 27, NASA's Fermi and Swift satellites detected a strong signal from the brightest gamma-ray burst in decades. Because this was relatively close, it was thousands of times brighter than the typical gamma-ray bursts that are seen by Swift every few days. Scientists are now scrambling to learn more.
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  19. #46
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    Here at Cosmoquest, you learn about these things the day they happen. :P

    EDIT: Huh. This was written by a professional, a professor in astronomy. And it still contains mistakes and untidy expressions...

    "If there is a supernova associated with this gamma-ray burst, a big optical flash should be seen any day now by ground-based telescopes, preceded by a flood of neutrinos. (The neutrinos are emitted at the time of collapse, while the optical light is the consequence of explosive debris hitting material surrounding the star a bit later.) [...] Now there is a real chance IceCube will make the first detection of astrophysical neutrinos, from the supernova associated with GRB130427A."
    The GRB is triggered by the core collapse, just as the SN. Neutrino emission is expected to be detected contemporaneous with the GRB, maybe preceeding it by some seconds. IceCube HAS reported observations of 130427A, and they found NOTHING. The Neutrino flare at core collapse is expected to be many magnitudes stronger than any late Neutroni flux from the afterglow or SN shock wave. They did not see anything during the burst, they will definitely not see anything now. Furthermore, the description of the SN is misleading (big optical flash) - we already hat that one, the SN will be about 14 magnitudes (!) fainter and evolve much more gradually over weeks.

    "Just nine days later, the bright nearby burst happened, leading to the Fermi detection of the highest energy gamma-ray ever."
    The highest energy from a GRB, yes. Atmospheric Cherenkov telescopes regularly probe gamma-rays at TeV energies.

    "When nuclear fusion uses up a star's fuel, in the central high-pressure stellar core where fusion occurs, the star will collapse fairly violently. Depending on its initial mass, it might collapse to a compact hot star known as a white dwarf (when the star's mass is less than 1.4 times the mass of our sun) or to a neutron star (for stars 1.4 to about three times the mass of our sun) or to a black hole (for stars more massive than three times the mass of our sun)."
    This is incorrect. What she means is the mass of the stellar core, not "the mass of the star", which anyone would read to be, say, the mass of the whole star at time of explosion, or, if your an astrophysicist, the Zero-Age Main Sequence mass.

    The Vela satellites were actually built to detect nuclear tests behind the MOON. It's when rough trigonometry showed GRBs to come from neither Earth, Sun, NOR Moon the conclusion had to be that they are natural cosmic events.

    Also, she writes GRB130427A, general nomenclature puts a space between GRB and the number.

    Finally, most of the article is not even really about the GRB itself.
    Last edited by Don Alexander; 2013-May-06 at 07:04 PM.

  20. #47
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    Quote Originally Posted by Don Alexander View Post
    IceCube HAS reported observations of 130427A, and they found NOTHING.
    Does this contradict theory or are we possibly going to find out how fast neutrinos (with mass) travel?

  21. #48
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    Well, the CNN article mentions the following: "Interestingly, an April 18 paper in the journal Nature reported that upper limits for neutrinos measured from IceCube are low enough that gamma-ray bursts are unlikely to be the sole source of ultra-high energy cosmic rays. Just nine days later, the bright nearby burst happened, leading to the Fermi detection of the highest energy gamma-ray ever."

    I just looked up the paper and saw it appeared on the 19th of April 2012. Not 2013...

    I think it is hard to state "this contradicts theory" since Theory in this case seems to be very vague and highle dependent on initial assumptions which are just plain guesses. The IceCube paper already wipes out a lot of models with simple assumptions that predicted high neutrino fluxes from GRBs. I expect the 130427A non-detection will remain one, and wipe out yet more large swathes of models. I kind of pity the Neutrino people, similar to gravitational waves, all they are doing is producing upper limits which rule out stuff...

    Furthermore, the first paper on 130427A has appeared:

    http://arxiv.org/abs/1305.1261

    I have of course not read it yet, but it presents analysis of (public) Swift and Fermi data.

  22. #49
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    Quote Originally Posted by Don Alexander View Post
    IceCube HAS reported observations of 130427A, and they found NOTHING.
    And very proud they are of getting the analysis time fast enough to release a GCN within 3 days of the event. One of their senior people is in the next office - when she mentioned that they'd gotten this analysis done, I figured it was a null result or she'd surely have kept mum for a big announcement.

    (Thematically related autocorrect error - Younger Son sent me a copy of the study guide for a final exam on Soviet history, which listed the two followers of Brezhnev as General Secretary: Andropov and Cherenkov. Fastest political leader in history!)

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    Sorry if my post was causing confusion..actually internet connection wasnt working properly ..that's why I had to close my browser frequently..One more question- GRB peak flux is the peak energy of the emitted photons in a second and the fluence is what has been emitted overthe entire duration of the burst,right? if tht's tru then fluence should always include the flux as well..like total isptropic energy always includes the peak lumnosity..But in the konus wind observations on GRB 110918A they calculated the isotropic equivalent energy release of 18A to be E_iso ~1.9x10^54 erg ,but the peak luminosity L_iso_max ~ 4.4x10^54 erg/s..How can the peak luminosity be bigger than the total energy itself? was it a huge typing mistake?

  24. #51
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    No, they simply measured peak luminosity over a small time window.

    "As observed by Konus-Wind the burst had a fluence of 7.5(-0.2,+0.2)x10-4 erg/cm2, and a 16-ms peak flux, measured from T0+0.368 s, of 8.7(-0.4,+0.4)x10-4 erg/cm2/s (both in the 20 keV - 10 MeV energy range)."

    There you have it, is measured over just 16 ms when the GRB was exhibiting the highest peak flux.

    In large samples, people sometimes measure peak flux as something like fluence/T_90, but if you have a the spectral and temporal resolution to do it, you should always measure peak flux (and luminosity) at the true peak.

    Short GRBs usually have much higher luminosity (per entire second) than they have actual E_iso.

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    ms means millisecond right? or is it used for microsecond also? So that means in reality GRBs don't emit in one second that much of energy unlike some Active galaxies/blazars whch at their peak emits really 10^39 watts in a second. For GRBs the millisecond flux is simply multiplied by a factor of 10^6 to calculate the Peak Flux it would have had it lasted for 1 second and then the peak luminosity(peak flux*4 pi*luminosity distance^2)?

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    Microsecond is Ás. ms is millisecond, so the factor is not 1E6, but in this case 0.016... Anyway, for a short timescale, the luminosity of GRBs far exceeds those of any quasar or other AGN.

    Also, since you complained that GRB luminoities were "exagerrated" because of the lack of beaming correction... Have you thought about the fact that quasar luminosities are also affected by beaming? Especially in the case of Blazars, which are actually very similar to GRBs in many ways.

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    I wasn't complaining or anything like that..I know isotropic calculations though exaggerated are standard ways of expression. Yep,blazars have always true power of 10^39 watts and they are magnified often by a factor of 1000(e.g. Famous 3C 454.3,PKS 1528+304,1622+297 etc . But quasars are not highly magnified(unless they are lensed),generally intrinsic powers are 0.87 times lesser than that of their iso emission. Whatever, in case of long GRBs like 130427a it's said their most energies are emitted within the first few seconds. And for GRB 130427A though it lasted for 2 and ahlf hours it was said that most of the energy was emitted during the first 18 seconds. So for the rest of the 2 hours did it only emit raDIO,x ray and UV? If that's the case then almost 99% of 27A's energy was emitted during the first 18 secs or so. And without detecting the afterglow is it possible to predict whther there was a jet break or not in any grb?

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    Quote Originally Posted by Only1Indrajit View Post
    ms means millisecond right? or is it used for microsecond also? So that means in reality GRBs don't emit in one second that much of energy unlike some Active galaxies/blazars whch at their peak emits really 10^39 watts in a second. For GRBs the millisecond flux is simply multiplied by a factor of 10^6 to calculate the Peak Flux it would have had it lasted for 1 second and then the peak luminosity(peak flux*4 pi*luminosity distance^2)?
    Watts are Joules per second. Watts per second is not a measure of power. If the value is given in Watts it already contains the time factor correction you are talking about - to compare total energy output you would need to multiply the power in Watts by the duration in seconds to get an energy output in Joules.

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    Yes I know the difrnc between joules and watts. No i was talking about 130427A. The prompt emission lasted for over 138 seconds,but most of the energy was released in the first 18 s. My question was how much of the total radiation could have been emitted within the frst few seconds which was said to be the Main Phase of 27A?

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    What's the chance we are dealing with magnetars on some of these? I recall SGR 1806 being a likely magnetar.

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    magnetars/NS-NS mergers cause short flares usually lasting for less than a second..these long bursts are collapsars,i.e., collpase and supernovae of massive Wolf Rayet stars

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    Quote Originally Posted by Only1Indrajit View Post
    Whatever, in case of long GRBs like 130427a it's said their most energies are emitted within the first few seconds. And for GRB 130427A though it lasted for 2 and ahlf hours
    Where did you get this number? Duration of GRBs is... iffy. What do you count? Usually T_90 of the gamma-ray emission - you check the entire emission duration and start summing the released fluence. When you reach 5%, you start T_90, when you reach 95%, you end it. This means GRBs with long, low-energy tails can be detected for significantly longer times than T_90. But also, T_90 is totally detector-dependent, and of course distance-dependant (and I am not talking about time dilation here, that is an additional effect). A soft tail will not be detected by an instrument that measures only harder gamma-rays (INTEGRAL SPI/ACS, Suzaku), whereas it is well detectable especially by Swift.
    The second point is what part do you call the GRB, and what the afterglow. Many GRBs have shown bright X-ray flares that were just faint enough to NOT have been detected in gammas, but are only explainable by continued central engine activity.
    Anyway, GRB 130427A was detected to about a day by Fermi LAT at > 100 MeV. That is more than 2.5 hours.
    Quote Originally Posted by Only1Indrajit View Post
    it was said that most of the energy was emitted during the first 18 seconds. So for the rest of the 2 hours did it only emit raDIO,x ray and UV?
    See above. But anyway, that is afterglow emission, not the actual GRB anymore.

    GRB 111209A, by the way, showed prompt emission of seven hours duration (or 60% of that if placed in the rest frame).
    Quote Originally Posted by Only1Indrajit View Post
    If that's the case then almost 99% of 27A's energy was emitted during the first 18 secs or so.
    Yes. But I do not see what the point is.

    In general, GRBs, in terms of luminosity, exceed anything and everything in the entire universe. Especially at gamma-ray energies, but also in the optical and the X-rays.

    In terms of total energy output, all wavebands, over the duration of the phenomenon, AGNs of course far exceed GRBs. The most luminous AGNs need roughly a few days to put out the same amount of energy a GRB puts out in seconds. More typical Quasars and especially Seyferts need years, decades, even centuries to reach that.
    Quote Originally Posted by Only1Indrajit View Post
    And without detecting the afterglow is it possible to predict whther there was a jet break or not in any grb?
    To my best knowledge, no, not at all. Well, your formulation is somewhat awry. If you write "to determine the jet break time without detecting the afterglow", then afaik, no. If it's "There's a GRB, can we predict that a jet break will occur some time?" then very likely yes, the emission is basically always collimated, there has to be a jet break somewhere.

    Speaking of this, there is so far no evidence for a jet break in 27A out to 1 Ms. (~10 days) Moreover, compared to an earlier decay slope, the decay has actually flattened. Using data up to 7 days, Fan et al. already find E_gamma, that is, collimation-corrected, exceeds 10^52 erg. So I'd say this GRB is starting to look quite special even beyond just being nearby...

    @George: There are models implicating magnetars in long GRBs. You get the core-collapse, but the core mass is just slightly beyond the Tolman-Oppenheimer-Volkov mass (whatever that exactly is...), and you do not produce a black hole but a super-massive, spin-stabilized magnetar. It emits copious amounts of energy by rapidly braking down due to its powerful magnetic field. This energy powers the GRB. The thing is, this is a good explanation for long-lasting, soft, low-luminosity smooth-envelope events like XRFs 060218 and 100316D, but unlikely to produce massive, shorter, spiky and hard GRBs like 130427A. Furthermore, the amount of energy that is extractable from neutron-star spindown can't exceed 10^52 erg, and certain GRBs (including this one, it seems) exceed this even after collimation correction.

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    [QUOTE=Don Alexander;2128254]Where did you get this number? Duration of GRBs is...
    I read it in http://en.wikipedia.org/wiki/Gamma-r...ion_mechanisms. Here it is written , in bursts as long as 100 seconds, the majority of the energy can be released in short episodes less than 1 second long. and also in the paper on 130427A -HIGH ENERGY EMISSION OF GRB 130427A: EVIDENCE FOR INVERSE COMPTON RADIATION it was stated that Most of the energy was released in the first  18 s thougfh the main phase of prompt emission lasted for 138 seconds. So that 10^52 ergs of energy must have been emitted within that 18-20 seconds period..coz afterglows dont contribute to the total output significantly

    Yes. But I do not see what the point is.

    In general, GRBs, in terms of luminosity, exceed anything and everything in the entire universe. Especially at gamma-ray energies, but also in the optical and the X-rays.

    In terms of total energy output, all wavebands, over the duration of the phenomenon, AGNs of course far exceed GRBs. The most luminous AGNs need roughly a few days to put out the same amount of energy a GRB puts out in seconds. More typical Quasars and especially Seyferts need years, decades, even centuries to reach that.

    I wasnt trying to compare grbs wth anything else in terms of luminosity ..the only thing that seemed little strange to me was that even for the long GRBs whose duration is more than 1 second Konus measures 16/64/256 milliseconds peak flux to calculate the luminosty ..

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