Albanova colloquium: Physics of gamma-ray bursts
The largest explosions that we have observed in the Universe are from the so called
gamma-ray bursts (GRBs). They are emitted in connection with the collapse of the
central regions of massive stellar remnants, into either a blackhole or a magnetar, and
a subsequent development of an ultra-relativistic jetted outflow. Since GRBs typically
occur at very large distances they have great potential for cosmology and the study
of the first generation stars.
However, the necessary basic understanding of the processes leading to the observed
gamma-ray emission is still incomplete. I will present the development of the current
paradigm which includes emission from the region in which the relativistic jet becomes
optically thin, the photosphere. In particular, I will review recent developments in our
understanding of the properties of a relativistic photosphere and the diagnostic tools
that are emerging from this study.