Exploring the Extreme Ends of the Gamma-Ray Burst Spectrum

Gamma-ray bursts (GRBs) are extreme phenomena: they are the brightest photon emitting events in the Universe, caused by a collimated ultra-relativistic flow, emerging from the deep potential well of a
collapsed object. They are observed across the whole electromagnetic spectrum, spanning almost 16 decades in observing frequency. Multi-wavelength observations of GRBs and their so-called afterglows are
used to study the physics of these extreme explosions, their progenitors and their surroundings. In this talk I will focus on the two extreme ends of the GRB spectrum: the prompt high-energy gamma-ray emission, in
particular the latest results obtained with the Fermi Gamma-ray Space Telescope (launched in June); and the low-frequency radio emission, which for a small number of GRBs can be observed for years after the initial
burst and provides unique information to constrain the physical models.

Alexander van der Horst

NASA MSFC