The Highest Magnetic Fields in the Universe: Anomalous X-Ray Pulsars and Soft Gamma-ray Repeaters

Abstract

In the last few years it has been recognized that two apparently distinct classes of peculiar high-energy sources are actually related and can be explained as young neutron stars with magnetic fields as high as 10e14 - 10e15 Gauss. One of these ''magnetars'', SGR 1806-20, has recently emitted the most powerful giant flare ever recorded. The high-energy observations of SGR 1806-20 carried out with XMM-Newton and INTEGRAL in the past two years showed a long term trend of increasing activity preceding the 2004 December 27 event. INTEGRAL data of this giant flare provided unique evidence for hard X-ray emission lasting about one hour after the burst onset, possibly due to the interaction of mildly relativistic ejecta with the circumstellar medium.