Anomalous X-ray Pulsars: Magnetar Candidates

Fotis Gavriil

Anomalous X-ray pulsars (AXPs) have been a mystery since the discovery of the the first example over twenty years ago. AXPs are rotating isolated neutron stars, and they are slowing down and therefore losing rotational kinetic energy. But unlike other isolated neutron stars this loss of rotational kinetic energy is not enough to explain their observed X-ray luminosity. The most promising AXP model is that they are young, ultra-magnetized neutron stars or `magnetars'. In this scenario it is the decay of their magnetic fields rather than rotation that is powering these pulsars. In order to test this and other models I have taken over a project to monitor all AXPs using NASA's Rossi X-ray Timing Explorer. I will discuss these observations and summarize how our work has effectively excluded a competing model for AXPs.