1207.1180 (J. Wang et al.)

Retrograde wind accretion -- an alternative mechanism for long spin periods of SFXTs    [PDF]

J. Wang, H. -K. Chang

A new class of high mass X-ray binaries (HMXBs) --- supergiant fast X-ray transients (SFXTs) --- are discovered by INTEGRAL, which are associated with OB supergiants and present long spin periods. There are observational evidences indicating that some accreting neutron stars in HMXBs display accretion reversals. It has been suggested that the inverted torque can lead to a very slow rotator. According to three characteristic radii in wind-fed accretion, we develop a retrograde accretion scenario and divide the accretion phase into three regimes, in order to interpret the formation of the long spin period of SFXTs. The accretion regime in some SFXT systems can be determined by their spin and orbital periods.

View original: http://arxiv.org/abs/1207.1180