Isolated thermal neutron stars, soft gamma-ray repeaters and anomalous X-ray pulsars: propellers and early accretors with conventional magnetic fields?

The similarity of rotation periods from three interesting classes of neutron stars, the anomalous X-ray pulsars (AXPs), the soft gamma ray repeaters (SGRs) and the dim isolated thermal neutron stars (DTNs) suggests a common mechanism with an asymptotic spindown phase, extending through the propeller and early accretion stages. The DTNs are interpreted as sources in the propeller stage. Their low luminosities arise from frictional heating in the neutron star. SGRs and AXPs are accreting at Ṁ ∼ 10gm/s. The limited range of near equilibrium periods corresponds to a limited range of mass inflow rates Ṁ . For lower rates the source of mass inflow may be depleted before the asymptotic stage is reached, while sources with higher Ṁ or later ages possess circumstellar material that is optically thick to electron scattering, destroying the X-ray