D. Konenkov et V. Urpin, The strong magnetic fields of the X-ray pulsars Hercules X-1 and 4U 1626-67 and their evolutionary scenarios, M NOT R AST, 301(1), 1998, pp. 175-178
We consider the magnetic and spin evolution of the X-ray binary pulsars Her
X-1 and 4U 1626-67, assuming that their magnetic fields are of crustal ori
gin. We adopt the standard evolutionary model which implies that the neutro
n star passes through several phases in a binary system ('isolated pulsar'
- propeller - wind accretion - Roche lobe overflow). In the framework of th
e model under consideration, the strong magnetic fields of relatively old p
ulsars like Her X-1 and 4U 1626-67 can naturally be understood if, at their
birth, they had a sufficiently strong magnetic field, similar to 3 x 10(13
) G, comparable to the maximal field observed in radio pulsars.