Gamma-ray bursts that are longer than two seconds are caused by the detonation of a rapidly rotating massive star at the end of its life on the main sequence. Jets of particles and gamma radiation are emitted in opposite directions from the stellar core as the star collapses. In this model, a narrow beam of gamma rays is emitted, followed by a wider beam of gamma rays. The narrow beam for GRB 080319B was aimed almost precisely at the Earth, which made it the brightest gamma-ray burst observed to date by NASA's Swift satellite.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 184.108.40.206.0