The Bright Optical Flash and Afterglow from the Gamma-Ray Burst GRB 130427A

Bright Lights Gamma-ray bursts (GRBs), bright flashes of gamma-ray light, are thought to be associated with the collapse of massive stars. GRB 130427A was detected on 27 April 2013, and it had the longest gamma-ray duration and one of the largest isotropic energy releases observed to date (see the Perspective by Fynbo). Ackermann et al. (p. 42, published online 21 November) report data obtained with the Fermi Gamma-Ray Space Telescope, which reveal a high-energy spectral component that cannot be accounted for by the standard external shock synchrotron radiation model. Vestrand et al. (p. 38, published online 21 November) report the detection of an extremely bright flash of visible light and unexpected similarities between the variations of optical light and the highest-energy gamma rays that indicate a common origin. A detailed analysis of the first pulse of GRB 130427A by Preece et al. (p. 51, published online 21 November) suggests that existing models cannot explain all the observed spectral and temporal behaviors simultaneously. Maselli et al. (p. 48, published online 21 November) present x-ray and optical light curves of the burst's prompt emission as well as of its afterglow as recorded by the Swift satellite and a range of ground-based telescopes. Multiwavelength data from an extremely bright stellar explosion provide details of the physics of these violent events. The optical light generated simultaneously with x-rays and gamma rays during a gamma-ray burst (GRB) provides clues about the nature of the explosions that occur as massive stars collapse. We report on the bright optical flash and fading afterglow from powerful burst GRB 130427A. The optical and >100–megaelectron volt (MeV) gamma-ray flux show a close correlation during the first 7000 seconds, which is best explained by reverse shock emission cogenerated in the relativistic burst ejecta as it collides with surrounding material. At later times, optical observations show the emergence of emission generated by a forward shock traversing the circumburst environment. The link between optical afterglow and >100-MeV emission suggests that nearby early peaked afterglows will be the best candidates for studying gamma-ray emission at energies ranging from gigaelectron volts to teraelectron volts.