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The image above shows the optical afterglow of gamma ray burst GRB-990123 taken on January 23, 1999. The burst is seen as a bright dot denoted by a square on the left, with an enlarged cutout on the right. The object above it with the finger-like filaments is the originating galaxy. This galaxy seems to be distorted by a collision with another galaxy.
The image above shows the optical afterglow of gamma ray burst GRB-990123 taken on January 23, 1999. GRB 990123 is a Gamma-ray burst that occurred on January 23 1999 (hence the designation Events 393 - Roman Emperor Theodosius I proclaims his nine year old son Honorius co-emperor Year 1999 ( MCMXCIX) was a Common year starting on Friday (link will display full 1999 Gregorian calendar) The burst is seen as a bright dot denoted by a square on the left, with an enlarged cutout on the right. The object above it with the finger-like filaments is the originating galaxy. This galaxy seems to be distorted by a collision with another galaxy.
Drawing of a massive star collapsing to form a black hole. Energy released as jets along the axis of rotation forms a gamma ray burst. Credit: Nicolle Rager Fuller/NSF
Drawing of a massive star collapsing to form a black hole. A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e Energy released as jets along the axis of rotation forms a gamma ray burst. Credit: Nicolle Rager Fuller/NSF

Gamma-ray bursts (GRBs) are the most luminous electromagnetic events occurring in the universe since the Big Bang. Luminosity has different meanings in several different fields of science Electromagnetism is the Physics of the Electromagnetic field: a field which exerts a Force on particles that possess the property of The Universe is defined as everything that Physically Exists: the entirety of Space and Time, all forms of Matter, Energy The Big Bang is the cosmological model of the Universe that is best supported by all lines of scientific evidence and Observation. They are flashes of gamma rays emanating from seemingly random places in deep space at random times. Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions The duration of a gamma-ray burst is typically a few seconds, but can range from a few milliseconds to minutes, and the initial burst is usually followed by a longer-lived "afterglow" emitting at longer wavelengths (X-ray, ultraviolet, optical, infrared, and radio). X-radiation (composed of X-rays) is a form of Electromagnetic radiation. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light. Gamma-ray bursts are detected by orbiting satellites about two to three times per week, but the number of GRBs that could be observed from Earth is about three times as many and it is currently limited by the efficiency of the instruments.

Most observed GRBs appear to be collimated emission caused by the collapse of the core of a rapidly rotating, high-mass star into a black hole. Collimated light is Light whose rays are nearly parallel and therefore will spread slowly as it propagates A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e A subclass of GRBs (the "short" bursts) appear to originate from a different process, the leading candidate being the collision of neutron stars orbiting in a binary system. A neutron star is a type of remnant that can result from the Gravitational collapse of a massive Star during a Type II, Type Ib or Type A binary star is a Star system consisting of two Stars orbiting around their Center of mass. All known GRBs originate from outside our own galaxy; though a related class of phenomena, SGR flares, are associated with Galactic magnetars. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply A soft gamma repeater ( SGR) is an astronomical object which emits large bursts of Gamma rays and X-rays at irregular intervals A magnetar is a Neutron star with an extremely powerful Magnetic field, the decay of which powers the emission of copious amounts of high-energy Electromagnetic The sources of most GRBs are billions of light years away. A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by

A nearby gamma ray burst could possibly cause mass extinctions on Earth. An extinction event (also known as mass extinction; extinction-level event, ELE is a sharp decrease in the number of Species in a relatively short period [1] Though the short duration of a gamma ray burst would limit the immediate damage to life, a nearby burst might alter atmospheric chemistry by reducing the ozone layer and generating acidic nitrogen oxides. An atmosphere (from Greek ατμός - atmos, " Vapor " + σφαίρα - sphaira, " Sphere " Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties The photochemical mechanisms that give rise to the ozone layer were worked out by the British physicist Sidney Chapman in 1930 The term nitrogen oxide typically refers to any Binary compound of Oxygen and Nitrogen, or to a mixture of such compounds Nitric These atmospheric changes could ultimately cause severe damage to the biosphere. The biosphere is the broadest level of ecological study the global sum of all Ecosystems.

Contents

Discovery and history

Cosmic gamma-ray bursts were discovered in the late 1960s by the US Vela nuclear test detection satellites. The United States of America —commonly referred to as the Vela was the name of a group of Satellites developed as the Vela Hotel element of Project Vela by the United States to monitor compliance with The Velas were built to detect gamma-radiation pulses emitted by nuclear weapon tests in space. The United States suspected that the USSR might attempt to conduct secret nuclear tests after signing the Nuclear Test Ban Treaty in 1963. The Union of Soviet Socialist Republics (USSR was a constitutionally Socialist state that existed in Eurasia from 1922 to 1991 The Treaty banning Nuclear Weapon Tests In The Atmosphere In Outer Space And Under Water, often abbreviated as the Partial Test Ban Treaty ( PTBT) Any discoveries of weapon tests have never been publicly declared and details of the Vela Incident, an as-yet unidentified flash of light over the South Atlantic on September 22, 1979, remain classified. The Vela Incident (sometimes referred to as the South Atlantic Flash) was an as-yet unidentified double flash of Light detected by a United States

In a classic example of scientific serendipity, the satellites did detect flashes of radiation that looked nothing like a nuclear weapons signature, coming from seemingly random directions in deep space. Serendipity is the effect by which one accidentally discovers something fortunate especially while looking for something else entirely These results were published in 1973,[2] prompting the scientific study of GRBs.

The presence of GRBs was confirmed later by many space missions such as Apollo and the Soviet Venera probes. The Venera (Венера series of probes was developed by the USSR between 1961 and 1984 to gather data from Venus. To explain these events, many speculative theories were advanced, most of which posited nearby galactic sources. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply Little progress was made however until the 1991 launch of the Compton Gamma Ray Observatory and its Burst and Transient Source Explorer (BATSE) instrument, an extremely sensitive gamma-ray detector. This instrument provided crucial data indicating that γ-ray bursts are isotropic[3] (not biased towards any particular direction in space, such as toward the galactic plane or the galactic center), and therefore ruling out nearly all galactic origins. Isotropy is uniformity in all directions Precise definitions depend on the subject area The galactic coordinate system is a Celestial coordinate system which is centered on the Sun and is aligned with the apparent center of the Milky Way galaxy The Galactic Center is the rotational center of the Milky Way Galaxy. BATSE data also showed that GRBs fall into two distinct categories: short-duration, hard-spectrum bursts ("short bursts"), and long-duration, soft-spectrum bursts ("long bursts"). [4] Short bursts are typically less than two seconds in duration and are dominated by higher-energy photons; long bursts are typically more than two seconds in duration and dominated by lower-energy photons. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena The separation is not absolute and the populations overlap observationally, but the distinction suggests two different classes of progenitors. However, some believe there are a third type of GRBs [5] [6] [7] [8] [9].

For decades after the discovery of GRBs astronomers could not find any counterpart or host to them, such as a star or galaxy, owing to poor resolution of their detectors. The best hope seemed to lie in finding a fainter, fading, longer wavelength emission after the burst itself, the "afterglow" of a GRB, as predicted by most models. Scientific modelling is the process of generating abstract, conceptual, Graphical and or mathematical models. [10]

In 1997 the Italian/Dutch satellite BeppoSAX detected a gamma-ray burst (GRB 970228)[11], and when the X-ray camera was pointed in direction from which the burst had originated it detected a fading X-ray emission. BeppoSAX was an Italian - Dutch Satellite for X-ray astronomy. Ground-based telescopes later identified a fading optical counterpart as well. [12] The location of this event having been identified, once the GRB faded, deep imaging was able to identify a faint, very distant host galaxy in the GRB location, the first of many to come. [13] Within only a few weeks the long controversy about the distance scale ended: GRBs were extragalactic events originating inside faint galaxies[14] at enormous distance. By finally establishing the distance scale, characterizing the environments in which GRBs occur, and providing a new window on GRBs both observationally and theoretically, this discovery revolutionized the study of GRBs. [15]

Swift Spacecraft
Swift Spacecraft

As of 2007, a similar revolution in GRB astronomy is in progress, largely as a result of successful launch of NASA's Swift satellite in November 2004, which combines a sensitive gamma-ray detector with the ability to slew on-board X-ray and optical telescopes towards the direction of a new burst in less than a minute. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program The Swift Gamma-Ray Burst Mission consists of a Robotic spacecraft called Swift, which was launched into Orbit on November 20, 2004 [16] Swift's discoveries include the first observations of short burst afterglows and vast amount of data on the behavior of GRB afterglows at early stages during their evolution, even before the GRB's gamma-ray emission has stopped. The mission has also discovered huge X-ray flares appearing within minutes to days after the end of the GRB.

Distance scale and energetics

Galactic vs. extragalactic models

Prior to the launch of BATSE, the distance scale to GRBs was completely unknown. Theories for the location of these events ranged from the outer regions of our own solar system to the edges of the known universe. The Solar System consists of the Sun and those celestial objects bound to it by Gravity. The discovery that bursts were isotropic—coming from completely random directions—narrowed down these possibilities greatly, and by the mid 1990s only two theories were considered generally viable: GRBs originate from a very large, diffuse halo (or "corona") around our own galaxy, or that they originate from distant galaxies far beyond our local group. The Local Group is the group of galaxies that includes our galaxy the Milky Way.

Supporters of the galactic model pointed to the class of well-known objects known as soft gamma repeaters (SGRs), highly magnetized galactic neutron stars known to periodically erupt in bright flares at gamma-ray and other wavelengths, and stated that there may be an unobserved population of similar objects at greater distances, producing GRBs. A soft gamma repeater ( SGR) is an astronomical object which emits large bursts of Gamma rays and X-rays at irregular intervals A neutron star is a type of remnant that can result from the Gravitational collapse of a massive Star during a Type II, Type Ib or Type [17] Furthermore, the sheer brightness of a typical gamma-ray burst would impose enormous requirements on the energy released in such an event if it really occurred in a distant galaxy.

Supporters of the extragalactic model claimed that the galactic neutron-star hypothesis involved too many ad-hoc assumptions in order to reproduce the degree of isotropy reported by BATSE and that an extragalactic model was far more natural regardless of its problems. [18]

The discovery of afterglow emission associated with faraway galaxies definitively supported the extragalactic hypothesis. Not only are GRBs extragalactic events, but they are also observable to the limits of the visible universe; a typical GRB has a redshift of at least 1. In Physics and Astronomy, redshift occurs when Electromagnetic radiation – usually Visible light – emitted or reflected by 0 (corresponding to a distance of 8 billion light-years), while the most distant known (GRB 050904) has a redshift of 6. GRB 050904 is the second most distant Gamma ray burst (GRB ever observed 29 (12. 3 billion light years). [19] As observers are able to acquire spectra of only a fraction of bursts - usually the brightest ones - many GRBs may actually originate from even higher redshifts.

GRB Jets: collimated emission

Many GRBs have been observed to undergo a jet break in their light curve, during which the optical afterglow quickly changes from slowly fading to rapidly fading as the jet slows down. In Astronomy, a light curve is a graph of light intensity of a Celestial object or region as a function of time [20] Furthermore, features suggestive of significant asymmetry have been observed in at least one nearby type Ic supernova, which may have the same progenitor stars as GRBs and have been observed to accompany GRBs in some cases (see "Progenitors"). Types Ib and Ic supernovae are categories of stellar explosions The jet opening angle (degree of beaming), however, varies greatly, from 2 degrees to more than 20 degrees. There is some evidence which suggests that the jet angles and apparent energy released are correlated in such a way that the true energy release of a (long) GRB is approximately constant—about 1044 J, or around 1/2000 of a solar mass. [21] This is comparable to the energy released in a bright type Ib/c supernova (sometimes termed a "hypernova"). A supernova (plural supernovae or supernovas) is a stellar Explosion. A supernova (plural supernovae or supernovas) is a stellar Explosion. Hypernova (pl hypernovae) refers to an exceptionally large Star that collapses at the end of its lifespan—for example a collapsar, or a large Bright hypernovae do in fact appear to accompany some GRBs. [22]

The fact that GRBs are jetted also suggests that there are far more events occurring in the Universe than actually seen, even when factoring in the limited sensitivity of available detectors. Most jetted GRBs will "miss" the Earth and never be seen; only a small fraction happen to be pointed the right way to allow detection. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 Still, even with these considerations, the rate of GRBs is very small—about once per galaxy per 100,000 years. [23]

Short GRBs

The above arguments apply only to long-duration GRBs. Short GRBs, while also extragalactic, appear to come from a lower-redshift population and are less luminous than long GRBs. [24] They appear to be generally less beamed[25] or possibly not beamed,[26] intrinsically less energetic than their longer counterparts, and probably more frequent in the universe despite being observed rarely.

Progenitors: what causes GRBs?

Main article: Gamma ray burst progenitors

The immense distances of most gamma-ray bursts has made pinning down the nature of the system that produces these explosions extremely difficult. Gamma-ray burst progenitors are the types of celestial objects that can emit Gamma-ray bursts (GRBs The currently favored model for the origin of most observed gamma-ray bursts is the collapsar model[27], in which the core of an extremely massive, low-metallicity, rapidly-rotating star collapses into a black hole, and the infall of material from the star onto the black hole powers an extremely energetic jet that blasts outward through the stellar envelope. Hypernova (pl hypernovae) refers to an exceptionally large Star that collapses at the end of its lifespan—for example a collapsar, or a large When the jet reaches the stellar surface, a gamma-ray burst is produced.

While the collapsar model has enjoyed a great deal of success, many other models exist that are still seriously considered. Winds from highly magnetized, newly-formed neutron stars (protomagnetars)[28], accretion-induced collapse of older neutron stars[29][30], and the mergers of binary neutron stars[31] have all been proposed as alternative models. The different models are not mutually exclusive, and it is possible that different bursts have different progenitors. For example, there is now good evidence that some short gamma-ray bursts (GRBs with a duration of less than about two seconds) occur in galaxies without massive stars[24], providing strong evidence that this subset of events are associated with a different progenitor population from longer bursts - for example, merging neutron stars. However, in 2007 the detection of 39 short gamma-ray bursts could not be associated with gravitational waves which are thought as observables of such compact mergers. In Physics, a gravitational wave is a Fluctuation in the Curvature of Spacetime which propagates as a wave, traveling outward from [32]

Emission mechanisms

Main article: Gamma ray burst emission mechanisms

The means by which gamma-ray bursts convert energy into radiation remains poorly understood, and as of 2007 there is still no generally accepted model for how this process occurs. Gamma ray burst emission mechanisms are theories that explain how the energy from a Gamma ray burst progenitor (regardless of the actual nature of the progenitor is turned into [33] A successful model of GRBs must explain not only the energy source, but also the physical process for generating an emission of gamma rays which matches the durations, light spectra, and other characteristics of observed GRBs. [34] The nature of the longer-wavelength (X-ray through radio) afterglow emission that follows gamma-ray bursts has been modeled much more successfully as synchrotron emission from a relativistic shock wave propagating through interstellar space [35] [36], but this model has had difficulty explaining the observed features of some observed GRB afterglows (particularly at early times and in the X-ray band)[37], and may be incomplete, or in some cases even inaccurate. A synchrotron is a particular type of cyclic Particle accelerator in which the magnetic field (to turn the particles so they circulate and the electric field (to accelerate

Mass extinction on Earth

Research has been conducted to investigate the consequences of Earth being hit by a beam of gamma rays from a nearby (about 500 light years) gamma ray burst. This is motivated by the efforts to explain mass extinctions on Earth and estimate the probability of extraterrestrial life. An extinction event (also known as mass extinction; extinction-level event, ELE is a sharp decrease in the number of Species in a relatively short period Extraterrestrial life is Life originating outside of the Earth. A gamma ray burst at 6000 light years would result in mass extinction; a 1000 light year distant burst would be equivalent to a 100,000 megaton nuclear explosion. A burst 100 light years away would blow away the atmosphere, create tidal waves, and start to melt the surface of the Earth. A consensus seems to have been arrived at the fact that damage by a gamma ray burst would be very limited because of its very short duration, and the fact that it would only cover half the Earth, the other half being in its shadow. A sufficiently close gamma ray burst would however, result in serious damage to the atmosphere, shutting down communications (due to electro-magnetic disturbances), perhaps instantly wiping out half the ozone layer, and causing nitrogen-oxygen recombination, thereby generating acidic nitrogen oxides. The photochemical mechanisms that give rise to the ozone layer were worked out by the British physicist Sidney Chapman in 1930 The term nitrogen oxide typically refers to any Binary compound of Oxygen and Nitrogen, or to a mixture of such compounds Nitric These effects could diffuse across to the other side of the Earth, severely diminish the global food supply, and result in long-term climate and atmospheric changes and a mass extinction, reducing the global population to perhaps 10% of what it can now support. An extinction event (also known as mass extinction; extinction-level event, ELE is a sharp decrease in the number of Species in a relatively short period However, the damage from a gamma ray burst would probably be significantly greater than a supernova at the same distance. A supernova (plural supernovae or supernovas) is a stellar Explosion.

The idea that a nearby gamma-ray burst could significantly affect the Earth's atmosphere and potentially cause severe damage to the biosphere was introduced in 1995 by physicist Stephen Thorsett, then at Princeton University. Stephen Erik Thorsett (b December 3, 1964 in New Haven Connecticut) is an American Professor and astronomer. Princeton University is a private Coeducational research university located in Princeton, New Jersey. [38] In 2005, scientists at NASA and the University of Kansas released a more detailed study which suggested that the Ordovician-Silurian extinction events which occurred 450 million years ago could have been triggered by a gamma-ray burst. The University of Kansas (often referred to as KU or just Kansas) is a public research university with campuses located in Lawrence, Kansas City The scientists do not have direct evidence to suggest that such a burst resulted in the ancient extinction, rather the strength of their work is their atmospheric modeling, essentially a "what if" scenario. The scientists calculated that gamma-ray radiation from a relatively nearby star explosion, hitting the Earth for only ten seconds, could deplete up to half of the atmosphere's protective ozone layer, the recovery for which would take at least five years. With the ozone layer damaged, ultraviolet radiation from the Sun would kill much of the life on land and near the surface of oceans and lakes, disrupting the food chain. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays Life is a state that distinguishes Organisms from non-living objects such as non-life and dead organisms being manifested by growth through Metabolism An ocean (from Greek, ''Okeanos'' (Oceanus) is a major body of saline water, and a principal component of the Hydrosphere. A lake (from Latin lacus) is a Terrain feature (or Physical feature) a body of Liquid on the surface of a world that is localized to the Food chains, also called food networks and/or trophic networks, describe the feeding relationships between species within an Ecosystem. While gamma-ray bursts in our Milky Way galaxy are indeed rare, NASA scientists estimate that at least one nearby event has probably hit the Earth in the past billion years. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply Life on Earth is at least 3. 5 billion years old. Dr. Bruce Lieberman, a paleontologist at the University of Kansas, originated the idea that a gamma-ray burst specifically could have caused the great Ordovician extinction. He said, "We do not know exactly when one came, but we're rather sure it did come - and left its mark. What's most surprising is that just a 10-second burst can cause years of devastating ozone damage. "[39]

Comparative work in 2006 on galaxies in which GRBs have occurred suggests that metal-deficient galaxies are the most likely candidates. The likelihood of the metal-rich Milky Way galaxy hosting a GRB was estimated at less than 0. 15%, significantly reducing the likelihood that a burst had caused mass extinction events on Earth. [40]

The Wolf-Rayet star WR 104, located 8000 light years from Earth, has been found to have a rotational axis aligned within 16° of the solar system. WR 104 is a Wolf-Rayet star located 8000 Light years from Earth at RA 18h02m04s The chances of it producing a gamma ray burst are small, but if it did, the GRB would be close enough to have a significant impact on Earth. [41]

Notable GRBs

GRBs of significant historical or scientific importance include:

See also

References

  1. ^ Melott, A. A supernova (plural supernovae or supernovas) is a stellar Explosion. Hypernova (pl hypernovae) refers to an exceptionally large Star that collapses at the end of its lifespan—for example a collapsar, or a large A soft gamma repeater ( SGR) is an astronomical object which emits large bursts of Gamma rays and X-rays at irregular intervals Gamma-ray astronomy is the astronomical study of the Cosmos with Gamma rays. Terrestrial gamma-ray flashes (TGFs are bursts of Gamma rays in the earth's atmosphere Stellar evolution is the process by which a Star undergoes a sequence of radical changes during its lifetime A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e L. , et al. (2004). "Did a gamma-ray burst initiate the late Ordovician mass extinction?". International Journal of Astrobiology 3: 55-61. doi:10.1017/S1473550404001910. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
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  13. ^ Not all scientists believed in this association at first, and the exact redshift of this particular galaxy was not obtained until many years later. However, the next well-localized gamma-ray burst, GRB 970508, had a firm absorption redshift of 0. 835 - a distance of 7 billion light years, and unambiguously far beyond our galaxy.
  14. ^ For more on galaxies hosting GRBs, see the GHostS database http://www.grbhosts.org
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  35. ^ Meszaros, P. and Rees, M. ~J. (1997). "Optical and Long-Wavelength Afterglow from Gamma-Ray Bursts". Astrophysical Journal 476: 476.  
  36. ^ Sari, R. ; Piran, T. ; Narayan, R. (1998). "Spectra and Light Curves of Gamma-Ray Burst Afterglows". Astrophysical Journal Letters 497: L17.  
  37. ^ Nousek, J. A. et al. (2006). "Evidence for a Canonical Gamma-Ray Burst Afterglow Light Curve in the Swift XRT Data". ApJ 642: 389-400. doi:10.1086/500724. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
  38. ^ Thorsett, S. E. (05/1995). "Terrestrial implications of cosmological gamma-ray burst models". Astrophysical Journal.  
  39. ^ Explosions in Space May Have Initiated Ancient Extinction on Earth. nasa. gov (June 4, 2005). Events 781 BC - The first historic Solar eclipse is recorded in China. Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Retrieved on 2007-09-15. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 668 - Eastern Roman Emperor Constans II is assassinated in his bath at Syracuse Italy.
  40. ^ One Less Thing to Worry About. astrobio. net (April 19, 2006). Events 1012 - Martyrdom of Alphege in Greenwich London. 1529 - At the Second Diet of Speyer Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Retrieved on 2007-09-15. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 668 - Eastern Roman Emperor Constans II is assassinated in his bath at Syracuse Italy.
  41. ^ badastronomy.com
  42. ^ Strong, Klebesadel, and Olson (February 15, 1974). Events 590 - Khosrau II is crowned as king of Persia 1637 - Ferdinand III becomes Holy Roman Emperor Year 1974 ( MCMLXXIV) was a Common year starting on Tuesday (link will display full calendar of the 1974 Gregorian calendar. "A Preliminary Catalog of Transient Cosmic Gamma-Ray Sources Observed by the Vela Satellites". The Astrophysical Journal 188: L1. American Astronomical Society. doi:10.1086/181415. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
  43. ^ Esin AA, Blandford R (2000). "Dust Echoes from Gamma-Ray Bursts". Astrophysical Journal 534 (2): L151-L154. The Astrophysical Journal (abbreviated to ApJ or Astrophys J) is a Scientific journal covering Astronomy and Astrophysics. PMID 10813670.  
  44. ^ Reichart, Daniel E. (February 19, 1998). Events 197 - Roman Emperor Septimius Severus defeats usurper Clodius Albinus in the Battle of Lugdunum Year 1998 ( MCMXCVIII) was a Common year starting on Thursday (link will display full 1998 Gregorian calendar) "The Redshift of GRB 970508". The Astrophysical Journal 495: L99. American Astronomical Society. doi:10.1086/311222. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
  45. ^ Sari, R. ; Piran, T. ; Halpern, J. P. (1999). "Jets in Gamma-Ray Bursts". Astrophysical Journal 519: L17-L20. doi:10.1086/312109. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
  46. ^ Frail, D. A. et al. (2001). "Beaming in Gamma-Ray Bursts: Evidence for a Standard Energy Reservoir". Astrophysical Journal 562: L55-L58. doi:10.1086/338119. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
  47. ^ Cosmic Cannon: How an Exploding Star Could Fry Earth. space. com (June 19, 2001). Events 1179 - The Norwegian Battle of Kalvskinnet outside Nidaros. Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar. Retrieved on 2007-10-10. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 680 - Battle of Karbala: Shia Imam Husayn bin Ali, the grandson of the Prophet Muhammad, is decapitated
  48. ^ GOTCHA! The Big One That Didn't Get Away. nasa. gov (January 27, 1999). Events 98 - Trajan becomes Roman Emperor after the death of Nerva. Year 1999 ( MCMXCIX) was a Common year starting on Friday (link will display full 1999 Gregorian calendar) Retrieved on 2007-10-10. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 680 - Battle of Karbala: Shia Imam Husayn bin Ali, the grandson of the Prophet Muhammad, is decapitated
  49. ^ N. Caldwell, et al. . GCN 2053, GRB 030329, optical spectroscopy.
  50. ^ T. Matheson, et al. . GCN 2120, GRB 030329: Supernova Confirmed.
  51. ^ P. W. Schnoor, et al. . GCN 2176, GRB030329 observed as a sudden ionospheric disturbance (SID).
  52. ^ Blast hints at black hole birth. bbc. co. uk (May 11, 2005). Events 330 - Byzantium is renamed ''Nova Roma'' during a dedication ceremony but is more popularly referred to as Constantinople Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Retrieved on 2007-10-10. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 680 - Battle of Karbala: Shia Imam Husayn bin Ali, the grandson of the Prophet Muhammad, is decapitated
  53. ^ Cosmic Explosion Could Be Black Hole Swallowing Neutron Star. nasa. gov (December 14, 2005). Events 1287 - St Lucia's flood: The Zuider Zee sea wall in the Netherlands collapses killing over 50000 people Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Retrieved on 2007-10-10. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 680 - Battle of Karbala: Shia Imam Husayn bin Ali, the grandson of the Prophet Muhammad, is decapitated
  54. ^ MOST DISTANT EXPLOSION DETECTED, SMASHES PREVIOUS RECORD. nasa. gov (September 12, 2005). Events 1213 - Albigensian Crusade: Simon de Montfort 5th Earl of Leicester, defeats Peter II of Aragon at the Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Retrieved on 2007-10-10. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 680 - Battle of Karbala: Shia Imam Husayn bin Ali, the grandson of the Prophet Muhammad, is decapitated
  55. ^ Strange Exploding Star Unlocks Supernova Secrets (August 30, 2006). Events 1363 - Beginning date of the Battle of Lake Poyang; the forces of two Chinese rebel leaders— Chen Youliang and Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Retrieved on 2007-10-10. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 680 - Battle of Karbala: Shia Imam Husayn bin Ali, the grandson of the Prophet Muhammad, is decapitated
  56. ^ Spatially resolved properties of the GRB 060505 host: implications for the nature of the progenitor. arxiv. org (March 15, 2007). Events 44 BC - Julius Caesar, Dictator of the Roman Republic, is stabbed to death by Marcus Junius Brutus, Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Retrieved on 2007-10-10. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 680 - Battle of Karbala: Shia Imam Husayn bin Ali, the grandson of the Prophet Muhammad, is decapitated
  57. ^ NASA Satellite Discovers New Kind of Black Hole Explosion. NASA (December 20, 2006). Events 69 - Vespasian, formerly a general under Nero, enters Rome to claim the title of Emperor. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Retrieved on 2007-11-11. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 308 - The Congress of Carnuntum: Attempting to keep peace within the Roman Empire, the leaders of the Tetrarchy declare
  58. ^ Gamma Ray Burst Coordinates Network. NASA (March 19, 2008). Events 1279 - A Mongolian victory in the Battle of Yamen ends the Song Dynasty in China. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Retrieved on 2008-03-20. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1600 - The Linköping Bloodbath takes place on Maundy Thursday in Linköping, Sweden.
  59. ^ Bloom, J. S. , et al. (2008). "Observations of the Naked-Eye GRB 080319B: Implications of Nature's Brightest Explosion". Astrophysical Journal: submitted.  

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