In gamma-ray astronomy, gamma-ray bursts (GRBs) are immensely energetic events occurring in distant galaxies which represent the brightest and "most powerful class of explosion in the universe." These extreme electromagnetic events are second only to the Big Bang as the most energetic and luminous phenomenon ever known. Gamma-ray bursts can last from a few milliseconds to several hours. After the initial flash of gamma rays, a longer-lived § afterglow is emitted, usually in the longer wavelengths of X-ray, ultraviolet, optical, infrared, microwave or radio frequencies.
NGC 300 (also known as Caldwell 70 or the Sculptor Pinwheel Galaxy) is a spiral galaxy in the constellation Sculptor. It was discovered on 5 August 1826 by Scottish astronomer James Dunlop. It is one of the closest galaxies to the Local Group, and it most likely lies between the latter and the Sculptor Group. It is the brightest of the five main spirals in the direction of the Sculptor Group. It is inclined at an angle of 42° when viewed from Earth and shares many characteristics of the Triangulum Galaxy. It is 94,000 light-years in diameter, somewhat smaller than the Milky Way, and has an estimated mass of (2.9 ± 0.2) × 1010M☉.
GRB 970228 was the first gamma-ray burst (GRB) for which an afterglow was observed. It was detected on 28 February 1997 at 02:58 UTC. Since 1993, physicists had predicted GRBs to be followed by a lower-energy afterglow, but until this event, GRBs had only been observed in highly luminous bursts of high-energy gamma rays ; this resulted in large positional uncertainties which left their nature very unclear.
The Gamma-Ray Burst Optical/Near-Infrared Detector (GROND) is an imaging instrument used to investigate Gamma-Ray Burst afterglows and for doing follow-up observations on exoplanets using transit photometry. It is operated at the 2.2-metre MPG/ESO telescope at ESO's La Silla Observatory in the southern part of the Atacama desert, about 600 kilometres north of Santiago de Chile and at an altitude of 2,400 metres.
GRB 970508 was a gamma-ray burst (GRB) detected on May 8, 1997, at 21:42 UTC; it is historically important as the second GRB with a detected afterglow at other wavelengths, the first to have a direct redshift measurement of the afterglow, and the first to be detected at radio wavelengths.
The history of gamma-ray began with the serendipitous detection of a gamma-ray burst (GRB) on July 2, 1967, by the U.S. Vela satellites. After these satellites detected fifteen other GRBs, Ray Klebesadel of the Los Alamos National Laboratory published the first paper on the subject, Observations of Gamma-Ray Bursts of Cosmic Origin. As more and more research was done on these mysterious events, hundreds of models were developed in an attempt to explain their origins.
GRB 090423 was a gamma-ray burst (GRB) detected by the Swift Gamma-Ray Burst Mission on April 23, 2009, at 07:55:19 UTC whose afterglow was detected in the infrared and enabled astronomers to determine that its redshift is z = 8.2, making it one of the most distant objects detected at that time with a spectroscopic redshift.
GRB 991216, nicknamed the Beethoven Burst by Dr. Brad Schaefer of Yale University, was a gamma-ray burst observed on December 16, 1999, coinciding with the 229th anniversary of Ludwig van Beethoven's birth. A gamma-ray burst is a highly luminous flash associated with an explosion in a distant galaxy and producing gamma rays, the most energetic form of electromagnetic radiation, and often followed by a longer-lived "afterglow" emitted at longer wavelengths.
GRB 000131 was a gamma-ray burst (GRB) that was detected on 31 January 2000 at 14:59 UTC. A gamma-ray burst is a highly luminous flash associated with an explosion in a distant galaxy and producing gamma rays, the most energetic form of electromagnetic radiation, and often followed by a longer-lived "afterglow" emitted at longer wavelengths.
GRB 011211 was a gamma-ray burst (GRB) detected on December 11, 2001. A gamma-ray burst is a highly luminous flash associated with an explosion in a distant galaxy and producing gamma rays, the most energetic form of electromagnetic radiation, and often followed by a longer-lived "afterglow" emitted at longer wavelengths.
GRB 030329 was a gamma-ray burst (GRB) that was detected on 29 March 2003 at 11:37 UTC. A gamma-ray burst is a highly luminous flash associated with an explosion in a distant galaxy and producing gamma rays, the most energetic form of electromagnetic radiation, and often followed by a longer-lived "afterglow" emitted at longer wavelengths. GRB 030329 was the first burst whose afterglow definitively exhibited characteristics of a supernova, confirming the existence of a relationship between the two phenomena.
GRB 070714B was a gamma-ray burst (GRB) that was detected on 14 July 2007 at 04:59 UTC. A gamma-ray burst is a highly luminous flash associated with an explosion in a distant galaxy and producing gamma rays, the most energetic form of electromagnetic radiation, and often followed by a longer-lived "afterglow" emitted at longer wavelengths.
GRB 090429B was a gamma-ray burst observed on 29 April 2009 by the Burst Alert Telescope aboard the Swift satellite. The burst triggered a standard burst-response observation sequence, which started 106 seconds after the burst. The X-ray telescope aboard the satellite identified an uncatalogued fading source. No optical or UV counterpart was seen in the UV–optical telescope. Around 2.5 hours after the burst trigger, a series of observations was carried out by the Gemini North telescope, which detected a bright object in the infrared part of the spectrum. No evidence of a host galaxy was found either by Gemini North or by the Hubble Space Telescope. Though this burst was detected in 2009, it was not until May 2011 that its distance estimate of 13.14 billion light-years was announced. With 90% likelihood, the burst had a photometric redshift greater than z = 9.06, which would make it the most distant GRB known, although the error bar on this estimate is large, providing a lower limit of z > 7.
A kilonova is a transient astronomical event that occurs in a compact binary system when two neutron stars or a neutron star and a black hole merge. These mergers are thought to produce gamma-ray bursts and emit bright electromagnetic radiation, called "kilonovae", due to the radioactive decay of heavy r-process nuclei that are produced and ejected fairly isotropically during the merger process. The measured high sphericity of the kilonova AT2017gfo at early epochs was deduced from the blackbody nature of its spectrum.
A hypernova is a very energetic supernova which is believed to result from an extreme core collapse scenario. In this case, a massive star collapses to form a rotating black hole emitting twin astrophysical jets and surrounded by an accretion disk. It is a type of stellar explosion that ejects material with an unusually high kinetic energy, an order of magnitude higher than most supernovae, with a luminosity at least 10 times greater. Hypernovae release such intense gamma rays that they often appear similar to a type Ic supernova, but with unusually broad spectral lines indicating an extremely high expansion velocity. Hypernovae are one of the mechanisms for producing long gamma ray bursts (GRBs), which range from 2 seconds to over a minute in duration. They have also been referred to as superluminous supernovae, though that classification also includes other types of extremely luminous stellar explosions that have different origins.
GRB 160625B was a bright gamma-ray burst (GRB) detected by NASA's Fermi Gamma-ray Space Telescope on 25 June 2016 and, three minutes later, by the Large Area Telescope. This was followed by a bright prompt optical flash, during which variable linear polarization was measured. This was the first time that these observations were made when the GRB was still bright and active. The source of the GRB was a possible black hole, within the Delphinus constellation, about 9 billion light-years (light travel distance) away (a redshift of z = 1.406). It had a fluence of 5.7×10−4 erg cm−2, and energy of 5 × 1054 erg. The burst lasted over 11 minutes (680 s), and is one of the most energetic bursts ever recorded.
A gamma-ray precursor is a short X-ray outburst event that comes before the main outburst of the gamma-ray burst progenitor. There is no consensus on the mechanism for this event, although several theories have been suggested.
GRB 190114C was an extreme gamma-ray burst explosion from a galaxy 4.5 billion light years away (z=0.4245; magnitude=15.60est) near the Fornax constellation, that was initially detected in January 2019. The afterglow light emitted soon after the burst was found to be tera-electron volt radiation from inverse Compton emission, identified for the first time. According to the astronomers, "We observed a huge range of frequencies in the electromagnetic radiation afterglow of GRB 190114C. It is the most extensive to date for a gamma-ray burst." Also, according to other astronomers, "light detected from the object had the highest energy ever observed for a GRB: 1 Tera electron volt (TeV)—about one trillion times as much energy per photon as visible light"; another source stated, "the brightest light ever seen from Earth [to date]."
GRB 221009A was an extraordinarily bright and very energetic gamma-ray burst (GRB) jointly discovered by the Neil Gehrels Swift Observatory and the Fermi Gamma-ray Space Telescope on October 9, 2022. The gamma-ray burst was ten minutes long, but was detectable for more than ten hours following initial detection. Despite being around 2.4 billion light-years away, it was powerful enough to affect Earth's atmosphere, having the strongest effect ever recorded by a gamma-ray burst on the planet. The peak luminosity of GRB 221009A was measured by Konus-Wind to be ~ 2.1 × 1047 W and by Fermi Gamma-ray Burst Monitor to be ~ 1.0 × 1047 W over its 1.024s interval. A burst as energetic and as close to Earth as 221009A is thought to be a once-in-10,000-year event. It was the brightest and most energetic gamma-ray burst ever recorded, with some dubbing it the BOAT, or Brightest Of All Time.
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