Rotational periods and other parameters of magnetars

Abstract

The rotational periods P, period derivatives dP/dt, and magnetic fields B in the region where the emission of anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) is generated are calculated using a model that associates the emission of these objects with the existence of drift waves at the periphery of the magnetosphere of a neutron star. The values obtained for these parameters are P = 11−737 ms, dP/dt = 3.7 × 10−16−5.5 × 10−12, and log B (G) = 2.63−6.25. We find a dependence between the X-ray luminosity of AXPs and SGRs, Lx, and the rate at which they lose rotational energy, dE/dt, which is similar to the Lx(dE/dt) dependence for radio pulsars with detected X-ray emission. Within the errors, AXPs/SGRs and radio pulsars with short periods (P < 0.1 s) display the same slopes for their log(dP/dt)-log P relations and for the dependence of the efficiency of their transformation of rotational energy into radiation on their periods. A dipole model is used to calculate the surface magnetic fields of the neutron stars in AXPs and SGRs, which turn out to be, on average, comparable to the surface fields of normal radio pulsars (〈log Bs (G)〉 = 11.90).