Editing Gamma-ray burst (section)

== Emission mechanisms ==
{{Main|Gamma-ray burst emission mechanisms}}
[[File:Gamma-ray-burst-Mechanism.jpg|thumb|left|400px|Gamma-ray burst mechanism]]
The means by which gamma-ray bursts convert energy into radiation remains poorly understood, and as of 2010 there was still no generally accepted model for how this process occurs.<ref>[[#Stern|Stern 2007]]</ref> Any successful model of GRB emission must explain the physical process for generating gamma-ray emission that matches the observed diversity of light curves, spectra, and other characteristics.<ref>[[#GFishman|Fishman, G. 1995]]</ref> Particularly challenging is the need to explain the very high efficiencies that are inferred from some explosions: some gamma-ray bursts may convert as much as half (or more) of the explosion energy into gamma-rays.<ref>[[#FanPiran|Fan & Piran 2006]]</ref> Early observations of the bright optical counterparts to [[GRB 990123]] and to [[GRB 080319B]], whose optical light curves were extrapolations of the gamma-ray light spectra,<ref name="Racusin" /><ref name="Liang Crider Boettcher Smith 1999">{{cite journal | last1=Liang | first1=E. P. | last2=Crider | first2=A. | last3=Boettcher | first3=M. | last4=Smith | first4=I. A. | title=GRB990123: The Case for Saturated Comptonization | journal=The Astrophysical Journal | date=1999-03-29 | volume=519 | issue=1 | pages=L21–L24 | doi=10.1086/312100 | bibcode=1999ApJ...519L..21L | s2cid=16005521 | arxiv=astro-ph/9903438 }}</ref> have suggested that [[Compton scattering|inverse Compton scattering]] may be the dominant process in some events. In this model, pre-existing low-energy [[photons]] are scattered by relativistic electrons within the explosion, augmenting their energy by a large factor and transforming them into gamma-rays.<ref>[[#Wozniak09|Wozniak 2009]]</ref>

The nature of the longer-wavelength afterglow emission (ranging from [[X-ray]] through [[radio waves|radio]]) that follows gamma-ray bursts is better understood. Any energy released by the explosion not radiated away in the burst itself takes the form of matter or energy moving outward at nearly the speed of light. As this matter collides with the surrounding [[interstellar gas]], it creates a [[relativistic speed|relativistic]] [[shock wave]] that then propagates forward into interstellar space. A second shock wave, the reverse shock, may propagate back into the ejected matter. Extremely energetic electrons within the shock wave are accelerated by strong local magnetic fields and radiate as [[synchrotron]] emission across most of the [[electromagnetic spectrum]].<ref>[[#Meszaros|Meszaros 1997]]</ref><ref>[[#Sari98|Sari 1998]]</ref> This model has generally been successful in modeling the behavior of many observed afterglows at late times (generally, hours to days after the explosion), although there are difficulties explaining all features of the afterglow very shortly after the gamma-ray burst has occurred.<ref>[[#Nousek|Nousek 2006]]</ref>
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