# Massive Gamma Ray Burst Still Lingers

The death of a star fifty times more massive than our Sun may well result in a hypernova, far more powerful than a supernova and, if you’re in line with the concentrated beam of its energies, far more luminous. Such events are hypothesized to be associated with long-duration gamma ray bursts (GRBs). We’ve just had a spectacular example of an apparent hypernova/GRB combination in the form of GRB 080319B, the record-holder for brightest naked eye object ever seen from Earth.

The image shows the fading light of this event as seen by the Hubble spacecraft on April 7. Bear in mind that the flash of gamma rays and other radiation was detected on March 19, at which point the GRB could be viewed at 5th magnitude in the constellation Boötes. The kicker is that a full three weeks after the explosion, the light of the galaxy in which this event originated is still drowned out by the light of the GRB.

Image: The gamma ray burst GRB 080319B leaves us with an optical remnant and a puzzle. What forces drive an explosion of this size, still glowing halfway across the visible universe? Credit: NASA, ESA, N. Tanvir (University of Leicester), A. Fruchter (STScI), A. Levan (University of Warwick), and E. Rol (University of Leicester).

Could such an explosion happen right here in our own galaxy, possibly threatening life on Earth? Probably not, according to Andrew Fruchter (Space Telescope Science Institute) and colleagues. Back in 2006 Fruchter’s team published work in Nature studying the environment of 42 long-duration bursts and 16 supernovae with Hubble. They were able to show that most long-duration GRBs occurred in small, irregular galaxies of the kind usually deficient in higher elements. Gamma ray bursts like this are therefore unlikely to occur in galaxies like the Milky Way. Fruchter noted the significance of the find:

“The discovery that long-duration gamma-ray bursts lie in the brightest regions of their host galaxies suggests that they come from the most massive stars – 20 or more times as massive as our Sun. Their occurrence in small irregulars implies that only stars that lack heavy chemical elements tend to produce long-duration GRBs.”

The implication is that long-duration events like GRB 080319B happened more often long ago, when galaxies were largely lacking in such elements. An accompanying theory is that a massive star rich in heavy elements loses too much material through its own stellar wind to house the mass needed to trigger a long-duration burst. The collapse of such a star might lead to a neutron star rather than a black hole, with no accompanying jet. So our own galaxy is unlikely to see an explosion like this one in the future, but we still have much to learn about the factors at work in keeping this particular afterglow so bright.

The 2006 paper is Fruchter et al., “Long gamma-ray bursts and core-collapse supernovae have different environments,” Nature Vol. 441 (2006), pp. 463-468 (available online).

Comments on this entry are closed.

• ljk April 15, 2008, 11:41

Correlation between regions of star formation and gamma-ray sources

Authors: K. Belotsky, A. Galper, B. Luchkov

(Submitted on 14 Apr 2008)

Abstract: Statistically significant correlation between positions of unidentified gamma-ray sources (UGS) and the regions of star formation (RSF) is found. Fraction of UGS, coincided in position with RSF, makes up $47\pm 8$%. The coincided discrete gamma-ray sources possess, on average, harder energetic spectra and larger intensities with respect to the rest UGS. Annihilation of dark matter concentrating in RSF is supposed to account for a possible origin of gamma-radiation.

Comments: 5 pages, 3 figures; report given at 29th Russian Conference on Cosmic Rays (3–7 Auguast 2006)

Subjects: Astrophysics (astro-ph)

Journal reference: `Bulletin of the Russian Academy of Sciences: Physics” v. 71 (2007), pp. 915-917

Cite as: arXiv:0804.2045v1 [astro-ph]

Submission history

From: Konstantin Belotsky M. [view email]

[v1] Mon, 14 Apr 2008 14:28:04 GMT (16kb)

http://arxiv.org/abs/0804.2045

• ljk April 15, 2008, 11:42

Bohdan’s Impact on Our Understanding of Gamma-ray Bursts

Authors: Tsvi Piran

(Submitted on 13 Apr 2008)

Abstract: Bohdan Paczy’nski was one of the pioneers of the cosmological GRB model. His ideas on how GRBs operate and what are their progenitors have dominated the field of GRBs in the hectic nineties during which the distances and the origin of GRBs were revealed. I discuss here Bohdan’s contributions in some historical perspective.

Comments: A talk given at The Variable Universe A Celebration of Bohdan Paczy’nski. To appear at the proccedings edited by Kris Stanek

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0804.2074v1 [astro-ph]

Submission history

From: Tsvi Piran [view email]

[v1] Sun, 13 Apr 2008 16:44:06 GMT (990kb)

http://arxiv.org/abs/0804.2074

• ljk April 15, 2008, 11:50

The prompt, high resolution spectroscopic view of the “naked-eye” GRB080319B

Authors: V. D’Elia, F. Fiore, R. Perna, Y. Krongold, S. Covino, D. Fugazza, D. Lazzati, F. Nicastro, L.A. Antonelli, S. Campana, G. Chincarini, P. D’Avanzo, M. Della Valle, P. Goldoni, D. Guetta, C. Guidorzi, E.J.A. Meurs, E. Molinari, L. Norci, S. Piranomonte, L. Stella, G. Stratta, G. Tagliaferri, P. Ward

(Submitted on 14 Apr 2008)

Abstract: GRB080319B reached 5th optical magnitude during the burst. Thanks to the VLT/UVES rapid response mode, we observed its afterglow just 8m:30s after the GRB onset when the magnitude was R ~ 12. This allowed us to obtain the best signal-to-noise, high resolution spectrum of a GRB afterglow ever (S/N per resolution element ~ 50). The spectrum is rich of absorption features belonging to the main system at z=0.937, divided in at least six components spanning a total velocity range of 100 km/s. The VLT/UVES observations caught the absorbing gas in a highly excited state, producing the strongest Fe II fine structure lines ever observed in a GRB. A few hours later the optical depth of these lines was reduced by a factor of 4-20, and the optical/UV flux by a factor of ~ 60.

This proves that the excitation of the observed fine structure lines is due to “pumping” by the GRB UV photons. A comparison of the observed ratio between the number of photons absorbed by the excited state and those in the Fe II ground state suggests that the six absorbers are $\gs18-34$ kpc from the GRB site, with component I ~ 2 times closer to the GRB site than components III to VI. Component I is characterized also by the lack of Mg I absorption, unlike all other components. This may be due to a higher gas temperature, suggesting a structured ISM in this galaxy complex.

Comments: 5 pages, 4 .ps figures, ApJL, submitted

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0804.2141v1 [astro-ph]

Submission history

From: Valerio D’Elia [view email]

[v1] Mon, 14 Apr 2008 10:44:41 GMT (33kb)

http://arxiv.org/abs/0804.2141

• Adam April 15, 2008, 16:09

Hi Paul

Opacity tends to be enhanced by increased Z fraction in stars, so low opacity in low Z stars means they’re bigger, on average, and – as your news indicates – more liable to blow as GRBs. Makes our galaxy’s very early days look increasingly unhealthy for life. Some SETI related questions follow…

Could James Annis be right about GRBs and the suppression of sentience in the early days of the Universe?

Could the terrestrial planet formation peak, of Lineweaver et al, be one reason why we don’t see a Galaxt full of astroengineers? Their homeworlds were bathed in GRBs and only recent aeons of our Galaxy have been conducive to Life.

Seems like there’s better odds that we’re amongst the first species to spring to “Galactic Super-Clade” status. The moral challenge is handling the petawatt directed energy tools of that prospect and not driving ourselves extinct.

• Administrator April 15, 2008, 17:13

Adam, I had wondered about Annis in this connection, too. I think I might re-visit those theories again, quite interesting stuff. As you point out, the interplay with Lineweaver makes for a view of the cosmos that makes sense and helps us with good old Fermi.

• James M. Essig April 15, 2008, 21:46

The power of this gamma ray burst is astounding. If by chance one of these happened in the Milky Way and was directed toward Earth, we could be fried with gamma ray energy. The interaction of the gamma ray burst’s ionizing radiation with the upper atmosphere could produce copious amounts of muons which could sterilize every thing on the planet down to a depth of several dozen meters below the ground on the side of the planet facing the burst.

Eta Carinae at a distance of about 8,000 LY strikes me as a potential hazard regardless of whether it produces a directed energy beam such as supposedly occurs with hypernova gamma ray burst phenomenon. Given that a type Ia supernovae or Carbon detonation supernova can perhaps be lethal to animal life on Earth even out to a distance of perhaps a few dozen light years, this bad boy with a mass of about 100 to 150 solar masses I feel poses some risk to our civilization even at a distance of some 300 times that of a Carbon detonation supernova’s lethal radius even for a spherically symmetric detonation.

Eta Carinae is just such an outlyer in terms of mass that I am not sure what the effects could be of even a spherical symmetric explosion let alone a directed energy beam explosion resulting from Eta Carinae’s demize might per chance have on an Earth in its gun sights.

I wonder if there could be any new physics at work in the explosion of a star so large. I assume not, but when and if this baby’s EM radiation first strikes Earth from its detonation, I only wish I could be around to see what happens if only out of vain curiosity.

Gamma ray burst are truely awesome and give us all reason to be humble at the enourmous energies of the events that take place within our universe.

Thanks;

We have never s

• Ronald April 16, 2008, 11:27

@James:

I could not find very accurate data (if they exist at all), but tentatively, what I have read (anybody correct me if I am wrong):
– that ‘ordinary’ supernovae are dangerous to an earthlike planet’s biosphere up to max. 20-30 ly;
– hypernovae with a spherical symmetric explosion up to about ten times that distance, so a few hundred ly;
– hypernovae with a ‘directed energy beam’ GRB up to a few thousand ly. But from what I have understood in the above article by Andrew Fruchter, these are not only extremely rare, but also mainly confined to the small metal-poor galaxies, unsuitable for planet formation.

Rather good news I would say, as if the universe was made to facilitate life ;-)

• Administrator April 16, 2008, 13:47

Or at least, Ronald, it’s as if the universe is made to order for life after a certain amount of time has passed to get the GRB phase over with! We’re going to re-examine that whole controversy again soon. It’s certainly timely given the recent GRB findings and the likelihood that we’ll be learning much more about the long-duration ones in the near future.

• James M. Essig April 17, 2008, 0:07

Hi Ronald;

Thanks for the clarifying comments on supernova danger radii. Even for these significantly reduced radii from the figures I suggested, I am still most impressed by the power of such explosions.

Hi Paul;

It is interesting to note that such large supernova may have been much more common in the past. I can see how highly evolved intellegent organisms might not have had a chance to take root with all of the powerful supernova occuring early on.

Thanks;

• James M. Essig April 17, 2008, 0:58

Hi Folks;

The idea involves beaming copious quantities of neutrinos of the right flavor(s) into a neutron star or perhaps some form of supersymmetric cold or hot dark matter in such a way that virtually all of the nuetrons within a neutron star would decay wherein a net electric charge imbalance of say 1 part in 10 EXP 9 would develope and wherein one tenth of the mass of the nuetron star would be converted into electrically charged particles simultaneously.

If such a net charge could be maintained without its dissolution into non-net charge though the many thermodynamic degrees of freedom available in particle interactions that might thus occur, then the tremendous coulombic force acting to explode that star could have a value as approximated by the following simplified calculations:

Fc ~ [1/(4 x pi x epsilon naght)]{[(10 EXP 12 Coulumbs)(10 EXP 20)] EXP 2}/[(10 EXP 4 meters) EXP 2] ~ (10 EXP 12)(10 EXP 64)(10 EXP – 8) Newtons = 10 EXP 68 Newtons. If the repulsive force was averaged over a distance of 10 kilometers in a two equally charged mass lumps approximation for which the average repulsive force was 10 EXP 68 newtons, then the energy released from the repulsion over the 10,000 meters would be 10 EXP 72 Newtons -meters or roughly two orders of magnitude greater than the entire mass/energy content of the observable universe.

Assumming that such a charge conservation violation can be artificially induced, it would be far to dangerous to do so in the current cosmic epoch. Perhaps when the universe has been greatly rarified over quadrillions of years of expansion, our distant relatives or perhaps ETI civilizations might find a use to stoke the mattergy content of our universe.

Matter-Antimatter assymetries are now known to occur in certain particle reactions, perhaps such large scale electrical charge violation can also be made manifest.

Thanks;

Jim

• James M. Essig April 17, 2008, 1:21

Hi Folks;

I am sorry for that yellow smiley face that appears in the above posting, although it is kind of cute. One can also imagine the much greater colombic force that would result if say 0.1 of the stars mass was converted into electric ally charged matter wherein a relative electric charge ratio of 99/100 would develope or a net imbalance of one part in 100 would develope.

Then the energy of repulsion over 10 EXP 4 meters would be 10 EXP 88 Joules or about 10 EXP 18 times the total mattergy of the observable universe.

Note that by net charge imbalance for the example given in my previous posting, I mean a relative charge ratio for the charged matter of 999,999,999/1,000,000,000.

I have no idea of the kind of particle reactions that would be required to induce such an imbalance let alone as to whether a huge blackhole might suddenly form out of the created energy as a result of the coloumbic force based explosions.

Thanks;

Jim

• ljk May 4, 2008, 23:06

What did we learn from gamma-ray burst 080319B ?

Authors: P. Kumar, A. Panaitescu

(Submitted on 1 May 2008)

Abstract: The optical and gamma-ray observations of GRB 080319B allow us to determine a fairly complete physical picture for this remarkable burst. The data indicate that the prompt optical and gamma-ray photons were produced at the same location but by different radiation processes: synchrotron and synchrotron self-Compton, respectively. The burst emission was produced at a distance of 10^{16.5} cm from the center of explosion by an ultra-relativistic source moving at Lorentz factor of ~500. A straightforward inference is that about 10 times more energy must have been radiated at tens of GeV than that released at ~1 MeV. Assuming that the GRB outflow was baryonic and that the gamma-ray source was shock-heated plasma, the collimation-corrected kinetic energy of the jet powering GRB 080319B was larger than 10^{52.3} erg. The decay of the early afterglow optical emission (up to 1 ks) is too fast to be attributed to the reverse shock crossing the GRB ejecta but is consistent with the expectations for the “large-angle emission” released during the burst. The pure power-law decay of the optical afterglow flux from 1 ks to 10 day is most naturally identified with the (synchrotron) emission from the shock propagating into a wind-like medium. However, the X-ray afterglow requires a departure from the standard blast-wave model.

Comments: 5 pages, submitted to MNRAS

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0805.0144v1 [astro-ph]

Submission history

From: Alin Panaitescu [view email]

[v1] Thu, 1 May 2008 20:08:40 GMT (60kb)

http://arxiv.org/abs/0805.0144

• ljk May 13, 2008, 14:42

GRB 080319B: A Naked-Eye Stellar Blast from the Distant Universe

Authors: J. L. Racusin, S.V. Karpov, M. Sokolowski, J. Granot, X. F. Wu, V. Pal’shin, S. Covino, A.J. van der Horst, S. R. Oates, P. Schady, R. J. Smith, J. Cummings, R.L.C. Starling, L. W. Piotrowski, B. Zhang, P.A. Evans, S. T. Holland, K. Malek, M. T. Page, L. Vetere, R. Margutti, C. Guidorzi, A. Kamble, P.A. Curran, A. Beardmore, C. Kouveliotou, L. Mankiewicz, A. Melandri, P.T. O’Brien, K.L. Page, T. Piran, N. R. Tanvir, G. Wrochna, R.L. Aptekar, C. Bartolini, S. Barthelmy, G. M. Beskin, S. Bondar, S. Campana, A. Cucchiara, M. Cwiok, P. D’Avanzo, V. D’Elia, M. Della Valle, W. Dominik, A. Falcone, F. Fiore, D. B. Fox, D. D. Frederiks, A. S. Fruchter, D. Fugazza, M. Garrett, N. Gehrels, S. Golenetskii, A. Gomboc, G. Greco, A. Guarnieri, S. Immler, G. Kasprowicz, A. J. Levan, et al. (24 additional authors not shown)

(Submitted on 11 May 2008)

Abstract: Long duration gamma-ray bursts (GRBs) release copious amounts of energy across the entire electromagnetic spectrum, and so provide a window into the process of black hole formation from the collapse of a massive star.

Over the last forty years, our understanding of the GRB phenomenon has progressed dramatically; nevertheless, fortuitous circumstances occasionally arise that provide access to a regime not yet probed. GRB 080319B presented such an opportunity, with extraordinarily bright prompt optical emission that peaked at a visual magnitude of 5.3, making it briefly visible with the naked eye. It was captured in exquisite detail by wide-field telescopes, imaging the burst location from before the time of the explosion. The combination of these unique optical data with simultaneous gamma-ray observations provides powerful diagnostics of the detailed physics of this explosion within seconds of its formation.

Here we show that the prompt optical and gamma-ray emissions from this event likely arise from different spectral components within the same physical region located at a large distance from the source, implying an extremely relativistic outflow.

The chromatic behaviour of the broadband afterglow is consistent with viewing the GRB down the very narrow inner core of a two-component jet that is expanding into a wind-like environment consistent with the massive star origin of long GRBs. These circumstances can explain the extreme properties of this GRB.

Comments: 43 pages, 18 figures, 3 tables, submitted to Nature May 11, 2008

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0805.1557v1 [astro-ph]

Submission history

From: Judith Racusin [view email]

[v1] Sun, 11 May 2008 19:32:42 GMT (2111kb)

http://arxiv.org/abs/0805.1557

• ljk May 22, 2008, 7:46

Gravitational collapse as the source of gamma-ray bursts

Authors: V.V.Sokolov

(Submitted on 21 May 2008)

Abstract: If the threshold for $e^{-}e^{+}$ pair production depends on an angle between photon momenta, and if the $\gamma$-rays are collimated right in gamma-ray burst (GRB) source then another solution of the compactness problem is possible. The list of basic assumptions of the scenario describing the GRB with energy release $< 10^{49}$ erg is adduced: the matter is about an alternative to the ultrarelativistic fireball if all long-duration GRBs are physically connected with core-collapse supernovae (SNe). The questions about radiation pressure and how the jet arises on account of even a small radiation field asymmetry in a compact GRB source of size $\lesssim 10^8$ cm, and observational consequences of the compact model of GRBs are considered.

Comments: 12 pages, no figures. To be published in Proceedings of the Conference “Problems of Practical Cosmology”, see this http URL

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0805.3262v1 [astro-ph]

Submission history

From: V. V. Sokolov [view email]

[v1] Wed, 21 May 2008 12:04:20 GMT (22kb)

http://arxiv.org/abs/0805.3262

• ljk June 13, 2008, 15:35

GRB 080319B: optical and gamma-ray emissions from internal forward-reverse shocks

Authors: Y. W. Yu, X. Y. Wang, Z. G. Dai

(Submitted on 12 Jun 2008)

Abstract: The temporal coincidence between the prompt $\gamma$-ray and optical emissions of gamma-ray burst (GRB) 080319B suggests that they may originate from a same emitting region or two regions sharing the same dynamical behavior. Meanwhile, the significant excess of the optical flux over the extrapolation of the $\gamma$-ray spectrum to the optical band indicates two different emission components.

We here consider the popular internal shock model where a forward and a reverse shock are generated simultaneously during a collision of two relativistic shells. In the case that the Lorentz factors of these two shocks are very different, the synchrotron emission driven by them could peak at two different energy bands.

We show that such a two-component synchrotron scenario can account for the prompt optical and $\gamma$-ray emissions of GRB 080319B under some unique conditions. In addition, the luminosity of an inverse-Compton sub-GeV or GeV component predicted in this scenario is not higher than that of synchrotron MeV gamma-rays, which could be tested by the {\em Gamma-ray Large Area Space Telescope} (GLAST).

Comments: 11 pages, submitted to ApJ Letters

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0806.2010v1 [astro-ph]

Submission history

From: Zigao Dai [view email]

[v1] Thu, 12 Jun 2008 06:57:54 GMT (10kb)

http://arxiv.org/abs/0806.2010