Strongly magnetized accreting NS are uniquely recognized by the observation of coherent X-ray pulsations with Ppulse > 0.1 s. The accreting material, when reaching the magnetospheric radius, is coupled to the magnetic field lines and channeled along those lines down to the surface of the NS at the magnetic poles. The released gravitational energy creates a hot spot with — 108K (Fig. 15.2). If the axis of rotation is inclined to the axis of the magnetic field (in the simplest form assumed to be a dipole field) any distant observer will see an X-ray pulsar, e.g., the X-ray flux is modulated at the spin frequency of the NS. In the X-ray spectra of half of these pulsars, cyclotron lines are observed, allowing the direct measurement of the field strength. These objects are referred to as accreting binary pulsars or accretion poweredX-ray pulsars. Two comprehensive reviews are  and .
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