After about 18 years of steadily spinning down, the accretion-powered pulsar 4U 1626-67, experienced a new torque reversal at the beginning of 2008. For the present study we have used all available Fermi/GBM data since its launch in 2008 June 11 and over 5 yr of hard X-ray Swift/BAT observations (starting from 2004 October up to the present time). From 2004 up to the end of 2007 the spin-down rate averaged at a mean rate of ∼ν = −4.8 × 10 −13 Hz s −1 until the torque reversal reported here. This second detected torque reversal was centered near MJD 54500 (2008 Feb 4) and it lasted approximately 150 days.During the reversal the source also underwent an increase in flux by a fraction of ∼2.5. Since then it has been following a steady spin-up at a mean rate of ∼ν = 4 × 10 −13 Hz s −1 . We present a detailed long-term timing analysis of this source and a long term spectral hardness ratio study in order to see whether there are spectral changes around this new observed torque reversal.

4U 2206+54 is a high mass X-ray binary which has been suspected to contain a neutron star accreting from the wind of its companion BD +53 • 2790. Reig et al. (2009) have recently detected 5560 s period pulsations in both RXTE and INTEGRAL observations which they conclude are due to the spin of the neutron star. We present observations made with Suzaku which are contemporaneous with their RXTE observation of this source. We find strong pulsations at a period of 5554 ± 9 s in agreement with their results. We also present a reanalysis of BeppoSAX observations of 4U 2206+54 made in 1998, in which we find strong pulsations at a period of 5420 ± 28 seconds, revealing a spin-down trend in this long-period accreting pulsar. Analysis of these data suggests that the neutron star in this system is an accretion-powered magnetar.

Several relatively bright, persistent X-ray sources display regular pulses, with periods in the range of 700-10000 s. These sources are identified with massive close binaries in which a neutron star accretes material onto its surface. The observed pulsations in all of them, but one, are unambiguously associated with the spin period of the neutron star. Analyzing possible history of these pulsars I conclude that the neutron stars in these systems undergo spherical accretion and their evolutionary tracks in a previous epoch contained three instead of two states, namely, ejector, supersonic propeller, and subsonic propeller. An assumption about a supercritical value of the initial magnetic field of the neutron stars within this scenario is not necessary. Furthermore, I show that the scenario in which the neutron star in 2S 0114+650 is assumed to be a magnetar descendant encounters major difficulties in explaining the evolution of the massive companion. An alternative interpretation of the spin evolution of the neutron star in this system is presented and the problem raised by association of the 10000 s pulsations with the spin period of the neutron star is briefly discussed.Comment: 7 pages, 2 tables, accepted for publication in MNRA