AXPs & SGRs: Magnetar or Quarctar?

The concept of a magnetar was proposed mainly because of two factors. First, the X-ray luminosity of Anomalous X-ray Pulsars (AXPs) and Soft Gamma-Ray Repeaters (SGRs) is larger than the rotational energy loss rate (Lx > E rot), and second, the magnetic field strength calculated from normal method is super strong. It is proposed that the radiation energy of magnetar comes from its magnetic fields. Here it is argued that the magnetic field strength calculated through the normal method is incorrect at the situation Lx > E rot, because the wind braking is not taken into account. Besides, the anti-magnetar and some other X-ray and radio observations are difficult to understand with a magnetar model. Instead of the magnetar, we propose a quarctar, which is a crusted quark star in an accretion disk, to explain the observations. In this model, the persistent X-ray emission, burst luminosity, spectrum of AXPs and SGRs can be understood naturally. The radio-emitting AXPs, which are challenging the magnetar, can also be explained by the quarctar model. © 2013 International Astronomical Union.