Editing Gamma-ray burst (section)

== Progenitors ==
{{Main|Gamma-ray burst progenitors}}
[[File:Wolf rayet2.jpg|thumb|Hubble Space Telescope image of [[Wolf–Rayet star]] [[WR 124]] and its surrounding nebula. Wolf–Rayet stars are candidates for being progenitors of long-duration GRBs.]]
Because of the immense distances of most gamma-ray burst sources from Earth, identification of the progenitors, the systems that produce these explosions, is challenging. The association of some long GRBs with supernovae and the fact that their host galaxies are rapidly star-forming offer very strong evidence that long gamma-ray bursts are associated with massive stars. The most widely accepted mechanism for the origin of long-duration GRBs is the [[Hypernova|collapsar]] model,<ref>[[#Mac99|MacFadyen 1999]]</ref> in which the core of an extremely massive, low-[[metallicity]], rapidly rotating star collapses into a [[black hole]] in the final stages of its [[stellar evolution|evolution]]. Matter near the star's core rains down towards the center and swirls into a high-density [[accretion disk]]. The infall of this material into a black hole drives a pair of [[relativistic jet]]s out along the rotational axis, which pummel through the stellar envelope and eventually break through the stellar surface and radiate as gamma rays. Some alternative models replace the black hole with a newly formed [[magnetar]],<ref>{{Cite journal |last1=Zhang |first1=Bing |last2=Mészáros |first2=Peter |s2cid=18660804 |date=2001-05-01 |title=Gamma-Ray Burst Afterglow with Continuous Energy Injection: Signature of a Highly Magnetized Millisecond Pulsar |bibcode=2001ApJ...552L..35Z |journal=The Astrophysical Journal Letters |volume=552 |issue=1 |pages=L35–L38 |doi=10.1086/320255 |arxiv = astro-ph/0011133 }}</ref><ref>{{Cite journal |last1=Troja |first1=E. |last2=Cusumano |first2=G. |last3=O'Brien |first3=P. T. |last4=Zhang |first4=B. |last5=Sbarufatti |first5=B. |last6=Mangano |first6=V. |last7=Willingale |first7=R. |last8=Chincarini |first8=G. |last9=Osborne |first9=J. P. |s2cid=14317593 |date=2007-08-01 |title=Swift Observations of GRB 070110: An Extraordinary X-Ray Afterglow Powered by the Central Engine |bibcode=2007ApJ...665..599T |journal=The Astrophysical Journal |volume=665 |issue=1 |pages=599–607 |doi=10.1086/519450 |arxiv = astro-ph/0702220 }}</ref> although most other aspects of the model (the collapse of the core of a massive star and the formation of relativistic jets) are the same.

The closest analogs within the Milky Way galaxy of the stars producing long gamma-ray bursts are likely the [[Wolf–Rayet star]]s, extremely hot and massive stars, which have shed most or all of their hydrogen envelope. [[Eta Carinae]], [[Apep (star system)|Apep]], and [[WR 104]] have been cited as possible future gamma-ray burst progenitors.<ref>[[#Plait|Plait 2008]]</ref> It is unclear if any star in the Milky Way has the appropriate characteristics to produce a gamma-ray burst.<ref name="Stanek">[[#Stanek|Stanek 2006]]</ref>

The massive-star model probably does not explain all types of gamma-ray burst. There is strong evidence that some short-duration gamma-ray bursts occur in systems with no star formation and no massive stars, such as elliptical galaxies and [[galaxy halo]]s.<ref name="SHBhosts" /> The favored hypothesis for the origin of most short gamma-ray bursts is the merger of a binary system consisting of two neutron stars. According to this model, the two stars in a binary slowly spiral towards each other because [[gravitational radiation]] releases energy<ref>[[#Abbott|Abbott 2007]]</ref><ref>[[#Kochanek|Kochanek 1993]]</ref> until [[tidal forces]] suddenly rip the neutron stars apart and they collapse into a single black hole. The infall of matter into the new black hole produces an accretion disk and releases a burst of energy, analogous to the collapsar model. Numerous other models have also been proposed to explain short gamma-ray bursts, including the merger of a neutron star and a black hole, the accretion-induced collapse of a neutron star, or the [[black hole evaporation|evaporation]] of [[primordial black hole]]s.<ref>[[#Vietri|Vietri 1998]]</ref><ref>[[#Mac2006|MacFadyen 2006]]</ref><ref>[[#Blinnikov|Blinnikov 1984]]</ref><ref name="cline">[[#Cline|Cline 1996]]</ref>

An alternative explanation proposed by [[Friedwardt Winterberg]] is that in the course of a gravitational collapse and in reaching the event horizon of a black hole, all matter disintegrates into a burst of gamma radiation.<ref>Winterberg, Friedwardt (2001 Aug 29). "Gamma-Ray Bursters and Lorentzian Relativity". Z. Naturforsch 56a: 889–892.</ref>

=== Tidal disruption events ===
{{Main|Tidal disruption event}}
This class of GRB-like events was first discovered through the detection of [[Swift J1644+57]] (originally classified as GRB 110328A) by the [[Swift Gamma-Ray Burst Mission]] on 28 March 2011. This event had a gamma-ray duration of about 2 days, much longer than even ultra-long GRBs, and was detected in many frequencies for months and years after. It occurred at the center of a small elliptical galaxy at redshift 3.8 billion light years away. This event has been accepted as a [[tidal disruption event]] (TDE), where a star wanders too close to a [[supermassive black hole]], shredding the star.  In the case of Swift J1644+57, an [[astrophysical jet]] traveling at near the speed of light was launched, and lasted roughly 1.5 years before turning off.<ref>{{cite news |last1=Cendes |first1=Yvette |title=How do black holes swallow stars? |url=https://www.astronomy.com/science/how-do-black-holes-swallow-stars/ |access-date=8 May 2024 |work=Astronomy Magazine |date=8 December 2021}}</ref>

Since 2011, only 4 jetted TDEs have been discovered, of which 3 were detected in gamma-rays (including Swift J1644+57).<ref name="TDE-jets">{{cite web |last1=Hensley |first1=Kerry |title=Why Are Jets from Disrupted Stars So Rare? |url=https://aasnova.org/2023/11/08/why-are-jets-from-disrupted-stars-so-rare/ |website=AAS Nova |date=8 November 2023}}</ref>  It is estimated that just 1% of all TDEs are jetted events.<ref name="TDE-jets" />