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The electromagnetic radiation often observed after a gamma-ray burst (GRB). As a shockwave of gas from a GRB ploughs into the surrounding gas and dust, kinetic energy is converted into radiation, creating the afterglow. The emission is synchrotron radiation from electrons accelerated in magnetic fields within the shock and can be observed at X-ray, optical, and radio wavelengths in succession as the shockwave expands and cools. The afterglow appears first hours to weeks after the initial GRB is detected, and later may be detected at longer wavelengths. It can last about a week as seen at X-ray wavelengths, for several weeks at optical wavelengths, and up to a year at radio wavelengths.

Subjects: Astronomy and Astrophysics.

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