Editing Gamma-ray burst (section)

== Classification ==
[[File:GRB BATSE 12lightcurves.png|thumb|Gamma-ray burst light curves]]The [[light curve]]s of gamma-ray bursts are extremely diverse and complex.<ref>[[#Katz|Katz 2002]], p. 37</ref> No two gamma-ray burst light curves are identical,<ref>[[#Marani|Marani 1997]]</ref> with large variation observed in almost every property: the duration of observable emission can vary from milliseconds to tens of minutes, there can be a single peak or several individual subpulses, and individual peaks can be symmetric or with fast brightening and very slow fading. Some bursts are preceded by a "[[Gamma-ray burst precursor|precursor]]" event, a weak burst that is then followed (after seconds to minutes of no emission at all) by the much more intense "true" bursting episode.<ref name="Lazzati">[[#Lazzati|Lazatti 2005]]</ref> The light curves of some events have extremely chaotic and complicated profiles with almost no discernible patterns.<ref name="CFishman">[[#CFishman|Fishman & Meegan 1995]]</ref>

Although some light curves can be roughly reproduced using certain simplified models,<ref>[[#Simic|Simić 2005]]</ref> little progress has been made in understanding the full diversity observed. Many classification schemes have been proposed, but these are often based solely on differences in the appearance of light curves and may not always reflect a true physical difference in the progenitors of the explosions. However, plots of the distribution of the observed duration<ref group="nb" name="T90">The duration of a burst is typically measured by T90, the duration of the period which 90 percent of the burst's [[energy]] is emitted. Recently some otherwise "short" GRBs have been shown to be followed by a second, much longer emission episode that when included in the burst light curve results in T90 durations of up to several minutes: these events are only short in the literal sense when this component is excluded.</ref> for a large number of gamma-ray bursts show a clear [[bimodal distribution|bimodality]], suggesting the existence of two separate populations: a "short" population with an average duration of about 0.3 seconds and a "long" population with an average duration of about 30 seconds.<ref name="Kouveliotou">[[#Kouveliotou|Kouveliotou 1994]]</ref> Both distributions are very broad with a significant overlap region in which the identity of a given event is not clear from duration alone. Additional classes beyond this two-tiered system have been proposed on both observational and theoretical grounds.<ref name="Horvath98">[[#Horvath98|Horvath 1998]]</ref><ref name="Hakkila">[[#Hakkila|Hakkila 2003]]</ref><ref name="Chattopadhyay">[[#Chattopadhyay|Chattopadhyay 2007]]</ref><ref name="Virgili">[[#Virgili|Virgili 2009]]</ref>

=== Short gamma-ray bursts ===
[[File:Hubble captures infrared glow of a kilonova blast.jpg|thumb|left|[[Hubble Space Telescope|Hubble]] image of the infrared glow of a [[kilonova]] blast.<ref>{{cite web|title=Hubble captures infrared glow of a kilonova blast |url=http://www.spacetelescope.org/images/opo1329a/|work=Image Gallery|publisher=ESA/Hubble |date=5 August 2013 |access-date=14 August 2013}}</ref>]][[File:GRB211106A.gif|thumb|GRB 211106A, one of the most energetic sGRB ever registered, in the first-ever time-lapse movie of a GRB in millimeter-wavelength light, as seen by the Atacama Large Millimeter/{{zwsp}}submillimeter Array (ALMA)<ref>{{Cite journal |last1=Laskar |first1=Tanmoy |last2=Escorial |first2=Alicia Rouco |last3=Schroeder |first3=Genevieve |last4=Fong |first4=Wen-fai |last5=Berger |first5=Edo |last6=Veres |first6=Péter |last7=Bhandari |first7=Shivani |last8=Rastinejad |first8=Jillian |last9=Kilpatrick |first9=Charles D. |last10=Tohuvavohu |first10=Aaron |last11=Margutti |first11=Raffaella |last12=Alexander |first12=Kate D. |last13=DeLaunay |first13=James |last14=Kennea |first14=Jamie A. |last15=Nugent |first15=Anya |date=2022-08-01 |title=The First Short GRB Millimeter Afterglow: The Wide-angled Jet of the Extremely Energetic SGRB 211106A |journal=The Astrophysical Journal Letters |volume=935 |issue=1 |pages=L11 |doi=10.3847/2041-8213/ac8421 |arxiv=2205.03419 |bibcode=2022ApJ...935L..11L |s2cid=248572470 |doi-access=free }}</ref><ref>{{Cite web |title=Out With a Bang: Explosive Neutron Star Merger Captured for the First Time in Millimeter Light |url=https://public.nrao.edu/news/neutron-star-merger-millimeter-alma/ |access-date=2022-08-14 |website=National Radio Astronomy Observatory |language=en-US}}</ref><ref>{{Cite web |title=Explosive neutron star merger captured for first time in millimeter light |url=https://news.northwestern.edu/stories/2022/08/explosive-neutron-star-merger-captured-for-first-time-in-millimeter-light/ |access-date=2022-08-14 |website=news.northwestern.edu |language=en}}</ref>]]Events with a duration of less than about two seconds are classified as short gamma-ray bursts (sGRB). These account for about 30% of gamma-ray bursts, but until 2005, no afterglow had been successfully detected from any short event and little was known about their origins.<ref name=r1>[http://www.nasa.gov/mission_pages/swift/bursts/short_burst_oct5.html In a Flash NASA Helps Solve 35-year-old Cosmic Mystery]. NASA (2005-10-05) The 30% figure is given here, as well as afterglow discussion.</ref> Following this, several dozen short gamma-ray burst afterglows were detected and localized, several of them associated with regions of little or no star formation, such as large [[elliptical galaxy|elliptical galaxies]].<ref>[[#Bloom06|Bloom 2006]]</ref><ref>[[#Hjorth|Hjorth 2005]]</ref><ref>[[#Gehrels05|Gehrels 2005]]</ref> This ruled out a link to massive stars, confirming the short events to be physically distinct from long events. In addition, there had been no association with supernovae.<ref name="Woosley06" />

The true nature of these objects was thus initially unknown, but the leading hypothesis was that they originated from the [[Neutron star merger|mergers of binary neutron stars]] or a neutron star with a [[black hole]]. Such mergers were hypothesized to produce [[kilonova]]e,<ref>{{Cite journal |last1=Li |first1=Li-Xin |last2=Paczyński |first2=Bohdan |date=1998-09-21 |title=Transient Events from Neutron Star Mergers |url=https://iopscience.iop.org/article/10.1086/311680/meta |journal=The Astrophysical Journal |language=en |volume=507 |issue=1 |pages=L59 |doi=10.1086/311680 |arxiv=astro-ph/9807272 |bibcode=1998ApJ...507L..59L |s2cid=3091361 |issn=0004-637X}}</ref> and evidence for a kilonova associated with short GRB 130603B was reported in 2013.<ref name=Tanvir2013>{{cite journal | doi = 10.1038/nature12505| pmid = 23912055| title = A 'kilonova' associated with the short-duration γ-ray burst GRB 130603B| journal = Nature| volume = 500| issue = 7464| pages = 547–549| year = 2013| last1 = Tanvir | first1 = N. R.| last2 = Levan | first2 = A. J.| last3 = Fruchter | first3 = A. S.| last4 = Hjorth | first4 = J.| last5 = Hounsell | first5 = R. A.| last6 = Wiersema | first6 = K.| last7 = Tunnicliffe | first7 = R. L.| s2cid = 205235329|arxiv = 1306.4971 |bibcode = 2013Natur.500..547T }}</ref><ref name=Dnews>{{cite web |url=http://news.discovery.com/space/astronomy/how-a-kilonova-solved-a-gamma-ray-burst-mystery-130807.htm |title=Kilonova Alert! Hubble Solves Gamma Ray Burst Mystery |access-date=22 January 2015 |date=7 August 2013 |website=Discovery News |first=Nicole |last=Gugliucci |archive-date=3 March 2016 |archive-url=https://web.archive.org/web/20160303182001/http://news.discovery.com/space/astronomy/how-a-kilonova-solved-a-gamma-ray-burst-mystery-130807.htm |url-status=dead }}</ref> The mean duration of sGRB events of around 200 milliseconds implied (due to [[Special relativity#Causality and prohibition of motion faster than light|causality]]) that the sources must be of very small physical diameter in stellar terms: less than 0.2 light-seconds (60,000&nbsp;km or 37,000 miles)—about four times the Earth's diameter. The observation of minutes to hours of X-ray flashes after an sGRB was seen as consistent with small particles of a precursor object like a neutron star initially being swallowed by a black hole in less than two seconds, followed by some hours of lower-energy events as remaining fragments of tidally disrupted neutron star material would remain in orbit, spiraling into the black hole over a longer period of time.<ref name=r1 />

The origin of short gamma-ray bursts in kilonovae was finally conclusively established in 2017, when short [[GRB 170817A]] co-occurred with the detection of gravitational wave [[GW170817]], a signal from the merger of two neutron stars.<ref name="PhysRev">{{cite journal|last1=Abbott|first1=B. P.|collaboration=[[LIGO Scientific Collaboration]] & [[Virgo interferometer|Virgo Collaboration]]|title=GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral|journal=Physical Review Letters|date=16 October 2017|volume=119|issue=16|pages=161101|doi=10.1103/PhysRevLett.119.161101|pmid=29099225|arxiv=1710.05832|bibcode=2017PhRvL.119p1101A|s2cid=217163611 }}</ref>

Unrelated to these cataclysmic origins, short-duration gamma-ray signals are also produced by giant flares from [[soft gamma repeaters]] in our own—or nearby—galaxies.<ref name="Frederiks">[[#Frederiks|Frederiks 2008]]</ref><ref>[[#Hurley05|Hurley 2005]]</ref>

=== Long gamma-ray bursts===
{{main category|Long-duration gamma-ray bursts}}
[[File:Xrt image crop.jpg|thumb|Swift captured the afterglow of [[GRB 221009A]] about an hour after it was first detected reaching Earth on October 9, 2022. The bright rings form as a result of X-rays scattered from otherwise unobservable dust layers within our galaxy that lie in the direction of the burst.]]Most observed events (70%) have a duration of greater than two seconds and are classified as long gamma-ray bursts. Because these events constitute the majority of the population and because they tend to have the brightest afterglows, they have been observed in much greater detail than their short counterparts. Almost every well-studied long gamma-ray burst has been linked to a galaxy with rapid star formation, and in many cases to a [[core-collapse supernova]] as well, unambiguously associating long GRBs with the deaths of massive stars.<ref name="Woosley06">[[#Woosley06|Woosley & Bloom 2006]]</ref><ref>{{Cite journal |last1=Hjorth |first1=Jens |last2=Sollerman |first2=Jesper |last3=Møller |first3=Palle |last4=Fynbo |first4=Johan P. U. |last5=Woosley |first5=Stan E. |last6=Kouveliotou |first6=Chryssa |last7=Tanvir |first7=Nial R. |last8=Greiner |first8=Jochen |last9=Andersen |first9=Michael I. |last10=Castro-Tirado |first10=Alberto J. |last11=Castro Cerón |first11=José María |last12=Fruchter |first12=Andrew S. |last13=Gorosabel |first13=Javier |last14=Jakobsson |first14=Páll |last15=Kaper |first15=Lex |date=2003-06-19 |title=A very energetic supernova associated with the γ-ray burst of 29 March 2003 |url=https://www.nature.com/articles/nature01750 |journal=Nature |language=en |volume=423 |issue=6942 |pages=847–850 |doi=10.1038/nature01750 |pmid=12815425 |issn=0028-0836|arxiv=astro-ph/0306347 |bibcode=2003Natur.423..847H }}</ref> Long GRB afterglow observations, at high redshift, are also consistent with the GRB having originated in star-forming regions.<ref name="Pontzen">[[#Pontzen|Pontzen et al. 2010]]</ref>

In December 2022, astronomers reported the observation of GRB&nbsp;211211A for 51 seconds, the first evidence of a long GRB likely associated with mergers of "compact binary objects" such as [[neutron star merger|neutron stars]] or [[white dwarf]]s.<ref>{{Cite journal |last1=Rastinejad |first1=Jillian C. |last2=Gompertz |first2=Benjamin P. |last3=Levan |first3=Andrew J. |last4=Fong |first4=Wen-fai |last5=Nicholl |first5=Matt |last6=Lamb |first6=Gavin P. |last7=Malesani |first7=Daniele B. |last8=Nugent |first8=Anya E. |last9=Oates |first9=Samantha R. |last10=Tanvir |first10=Nial R. |last11=de Ugarte Postigo |first11=Antonio |last12=Kilpatrick |first12=Charles D. |last13=Moore |first13=Christopher J. |last14=Metzger |first14=Brian D. |last15=Ravasio |first15=Maria Edvige |date=2022-12-08 |title=A kilonova following a long-duration gamma-ray burst at 350 Mpc |url=https://www.nature.com/articles/s41586-022-05390-w |journal=Nature |language=en |volume=612 |issue=7939 |pages=223–227 |doi=10.1038/s41586-022-05390-w |pmid=36477128 |issn=0028-0836|arxiv=2204.10864 |bibcode=2022Natur.612..223R }}</ref><ref>{{Cite journal |last1=Troja |first1=E. |last2=Fryer |first2=C. L. |last3=O’Connor |first3=B. |last4=Ryan |first4=G. |last5=Dichiara |first5=S. |last6=Kumar |first6=A. |last7=Ito |first7=N. |last8=Gupta |first8=R. |last9=Wollaeger |first9=R. T. |last10=Norris |first10=J. P. |last11=Kawai |first11=N. |last12=Butler |first12=N. R. |last13=Aryan |first13=A. |last14=Misra |first14=K. |last15=Hosokawa |first15=R. |date=2022-12-08 |title=A nearby long gamma-ray burst from a merger of compact objects |journal=Nature |language=en |volume=612 |issue=7939 |pages=228–231 |doi=10.1038/s41586-022-05327-3 |issn=0028-0836 |pmc=9729102 |pmid=36477127|arxiv=2209.03363 |bibcode=2022Natur.612..228T }}</ref><ref>{{Cite web |date=2022-12-07 |title=Kilonova Discovery Challenges our Understanding of Gamma-Ray Bursts |url=https://www.gemini.edu/pr/kilonova-discovery-challenges-our-understanding-gamma-ray-bursts |access-date=2022-12-11 |website=Gemini Observatory |language=en}}</ref> Following this, GRB&nbsp;191019A (2019, 64s)<ref>{{Cite journal |last1=Levan |first1=Andrew J. |last2=Malesani |first2=Daniele B. |last3=Gompertz |first3=Benjamin P. |last4=Nugent |first4=Anya E. |last5=Nicholl |first5=Matt |last6=Oates |first6=Samantha R. |last7=Perley |first7=Daniel A. |last8=Rastinejad |first8=Jillian |last9=Metzger |first9=Brian D. |last10=Schulze |first10=Steve |last11=Stanway |first11=Elizabeth R. |last12=Inkenhaag |first12=Anne |last13=Zafar |first13=Tayyaba |last14=Agüí Fernández |first14=J. Feliciano |last15=Chrimes |first15=Ashley A. |date=2023-06-22 |title=A long-duration gamma-ray burst of dynamical origin from the nucleus of an ancient galaxy |url=https://www.nature.com/articles/s41550-023-01998-8 |journal=Nature Astronomy |language=en |volume=7 |issue=8 |pages=976–985 |doi=10.1038/s41550-023-01998-8 |issn=2397-3366|arxiv=2303.12912 |bibcode=2023NatAs...7..976L }}</ref> and [[GRB 230307A]] (2023, 35s)<ref>{{cite web |title=GCN - Circulars - 33410: Solar Orbiter STIX observation of GRB 230307A |url=https://gcn.nasa.gov/circulars/33410}}</ref><ref>{{cite web |title=GCN - Circulars - 33412: GRB 230307A: AGILE/MCAL detection |url=https://gcn.nasa.gov/circulars/33412}}</ref> have been argued to signify an emerging class of long GRB which may originate from these types of progenitor events.<ref>{{Cite web |last=Wodd |first=Charlie |date=11 December 2023 |title=Extra-Long Blasts Challenge Our Theories of Cosmic Cataclysms |url=https://www.quantamagazine.org/extra-long-blasts-challenge-our-theories-of-cosmic-cataclysms-20231211/ |website=[[Quanta magazine]]}}</ref>

=== Ultra-long gamma-ray bursts ===
ulGRB are defined as GRB lasting more than 10,000 seconds, covering the upper range to the limit of the GRB duration distribution. They have been proposed to form a separate class, caused by the collapse of a [[blue supergiant|blue supergiant star]],<ref>{{cite journal |bibcode=2013ApJ...766...30G |doi=10.1088/0004-637X/766/1/30 |title=The Ultra-Long Gamma-Ray Burst 111209A: The Collapse of a Blue Supergiant? |journal=The Astrophysical Journal |volume=766 |issue=1 |page=30 |date=2013 |last1=Gendre |first1=B. |last2=Stratta |first2=G. |last3=Atteia |first3=J. L. |last4=Basa |first4=S. |last5=Boër |first5=M. |last6=Coward |first6=D. M. |last7=Cutini |first7=S. |last8=d'Elia |first8=V. |last9=Howell |first9=E. J |last10=Klotz |first10=A. |last11=Piro |first11=L. |s2cid=118618287 |arxiv = 1212.2392 }}</ref> a [[tidal disruption event]]<ref name="Greiner Mazzali Kann Krühler pp. 189–192">{{cite journal | last1=Greiner | first1=Jochen | last2=Mazzali | first2=Paolo A. | last3=Kann | first3=D. Alexander | last4=Krühler | first4=Thomas | last5=Pian | first5=Elena | last6=Prentice | first6=Simon | last7=Olivares E. | first7=Felipe | last8=Rossi | first8=Andrea | last9=Klose | first9=Sylvio | last10=Taubenberger | first10=Stefan | last11=Knust | first11=Fabian | last12=Afonso | first12=Paulo M. J. | last13=Ashall | first13=Chris | last14=Bolmer | first14=Jan | last15=Delvaux | first15=Corentin | last16=Diehl | first16=Roland | last17=Elliott | first17=Jonathan | last18=Filgas | first18=Robert | last19=Fynbo | first19=Johan P. U. | last20=Graham | first20=John F. | last21=Guelbenzu | first21=Ana Nicuesa | last22=Kobayashi | first22=Shiho | last23=Leloudas | first23=Giorgos | last24=Savaglio | first24=Sandra | last25=Schady | first25=Patricia |author25-link= Patricia Schady | last26=Schmidl | first26=Sebastian | last27=Schweyer | first27=Tassilo | last28=Sudilovsky | first28=Vladimir | last29=Tanga | first29=Mohit | last30=Updike | first30=Adria C. | last31=van Eerten | first31=Hendrik | last32=Varela | first32=Karla | s2cid=4464998 | title=A very luminous magnetar-powered supernova associated with an ultra-long γ-ray burst | journal=Nature | volume=523 | issue=7559 | date=2015-07-08  | doi=10.1038/nature14579 | pmid=26156372 | display-authors=29 | pages=189–192|arxiv = 1509.03279 |bibcode = 2015Natur.523..189G }}</ref><ref name="Levan Tanvir Starling Wiersema">{{cite journal | last1=Levan | first1=A. J. | last2=Tanvir | first2=N. R. | last3=Starling | first3=R. L. C. | last4=Wiersema | first4=K. | last5=Page | first5=K. L. | last6=Perley | first6=D. A. | last7=Schulze | first7=S. | last8=Wynn | first8=G. A. | last9=Chornock | first9=R. | last10=Hjorth | first10=J. | last11=Cenko | first11=S. B. | last12=Fruchter | first12=A. S. | last13=O'Brien | first13=P. T. | last14=Brown | first14=G. C. | last15=Tunnicliffe | first15=R. L. | last16=Malesani | first16=D. | last17=Jakobsson | first17=P. | last18=Watson | first18=D. | last19=Berger | first19=E. | last20=Bersier | first20=D. | last21=Cobb | first21=B. E. | last22=Covino | first22=S. | last23=Cucchiara | first23=A. | last24=de Ugarte Postigo | first24=A. | last25=Fox | first25=D. B. | last26=Gal-Yam | first26=A. | last27=Goldoni | first27=P. | last28=Gorosabel | first28=J. | last29=Kaper | first29=L. | last30=Krühler | first30=T. | last31=Karjalainen | first31=R. | last32=Osborne | first32=J. P. | last33=Pian | first33=E. | last34=Sánchez-Ramírez | first34=R. | last35=Schmidt | first35=B. | last36=Skillen | first36=I. | last37=Tagliaferri | first37=G. | last38=Thöne | first38=C. | last39=Vaduvescu | first39=O. | last40=Wijers | first40=R. A. M. J. | last41=Zauderer | first41=B. A. | title=A new population of ultra-long duration gamma-ray bursts | journal=The Astrophysical Journal | volume=781 | issue=1 | year=2014 |display-authors=29 | arxiv=1302.2352 | doi=10.1088/0004-637x/781/1/13 | page=13 | bibcode=2014ApJ...781...13L| s2cid=24657235 }}</ref> or a new-born [[magnetar]].<ref name="Greiner Mazzali Kann Krühler pp. 189–192" /><ref name="Ioka Hotokezaka Piran p=110">{{cite journal | last1=Ioka | first1=Kunihito | last2=Hotokezaka | first2=Kenta | last3=Piran | first3=Tsvi | s2cid=118629696 | title=Are Ultra-Long Gamma-Ray Bursts Caused by Blue Supergiant Collapsars, Newborn Magnetars, or White Dwarf Tidal Disruption Events? | journal=The Astrophysical Journal | volume=833 | issue=1 | date=2016-12-12  | doi=10.3847/1538-4357/833/1/110 | page=110|arxiv = 1608.02938 |bibcode = 2016ApJ...833..110I | doi-access=free }}</ref> Only a small number have been identified to date, their primary characteristic being their gamma ray emission duration. The most studied ultra-long events include [[GRB 101225A]] and [[GRB 111209A]].<ref name="Levan Tanvir Starling Wiersema"/><ref>{{cite journal |arxiv=1310.4944 |last1=Boer |first1=Michel |title=Are Ultra-long Gamma-Ray Bursts different? |journal=The Astrophysical Journal |volume=800 |issue=1 |pages=16 |last2=Gendre |first2=Bruce |last3=Stratta |first3=Giulia |s2cid=118655406 |doi=10.1088/0004-637X/800/1/16 |date=2013 |bibcode = 2015ApJ...800...16B }}</ref><ref>{{cite journal |bibcode=2013ApJ...778...54V |doi=10.1088/0004-637X/778/1/54 |title=Grb 091024A and the Nature of Ultra-Long Gamma-Ray Bursts |journal=The Astrophysical Journal |volume=778 |issue=1 |page=54 |date=2013 |last1=Virgili |first1=F. J. |last2=Mundell |first2=C. G. |last3=Pal'Shin |first3=V. |last4=Guidorzi |first4=C. |last5=Margutti |first5=R. |last6=Melandri |first6=A. |last7=Harrison |first7=R. |last8=Kobayashi |first8=S. |last9=Chornock |first9=R. |last10=Henden |first10=A. |last11=Updike |first11=A. C. |last12=Cenko |first12=S. B. |last13=Tanvir |first13=N. R. |last14=Steele |first14=I. A. |last15=Cucchiara |first15=A. |last16=Gomboc |first16=A. |last17=Levan |first17=A. |last18=Cano |first18=Z. |last19=Mottram |first19=C. J. |last20=Clay |first20=N. R. |last21=Bersier |first21=D. |last22=Kopač |first22=D. |last23=Japelj |first23=J. |last24=Filippenko |first24=A. V. |last25=Li |first25=W. |last26=Svinkin |first26=D. |last27=Golenetskii |first27=S. |last28=Hartmann |first28=D. H. |last29=Milne |first29=P. A. |last30=Williams |first30=G. |s2cid=119023750 |display-authors=29 |arxiv = 1310.0313 }}</ref> The low detection rate may be a result of low sensitivity of current detectors to long-duration events, rather than a reflection of their true frequency.<ref name="Levan Tanvir Starling Wiersema"/> A 2013 study,<ref>{{cite journal |arxiv=1310.2540 |last1=Zhang |first1=Bin-Bin |title=How Long does a Burst Burst? |journal=The Astrophysical Journal |volume=787 |issue=1 |page=66 |last2=Zhang |first2=Bing |last3=Murase |first3=Kohta |last4=Connaughton |first4=Valerie |last5= Briggs |first5=Michael S. |s2cid=56273013 |year=2014 |doi=10.1088/0004-637X/787/1/66 |bibcode = 2014ApJ...787...66Z }}</ref> on the other hand, shows that the existing evidence for a separate ultra-long GRB population with a new type of progenitor is inconclusive, and further multi-wavelength observations are needed to draw a firmer conclusion.