Magnetars: neutron stars with huge magnetic storms
  Among the many different classes of stellar objects, neutron stars provide a
unique environment where we can test (at the same time) our understanding of
matter with extreme density, temperature, and magnetic field. In particular,
the properties of matter under the influence of magnetic fields and the role of
electromagnetism in physical processes are key areas of research in physics.
However, despite decades of research, our limited knowledge on the physics of
strong magnetic fields is clear: we only need to note that the strongest steady
magnetic field achieved in terrestrial labs is some millions of Gauss, only
thousands of times stronger than a common refrigerator magnet. In this general
context, I will review here the state of the art of our research on the most
magnetic objects in the Universe, a small sample of neutron stars called
magnetars. The study of the large high-energy emission, and the flares from
these strongly magnetized (~10^{15} Gauss) neutron stars is providing crucial
information about the physics involved at these extremes conditions, and
favoring us with many unexpected surprises.
