We present timing and spectral analysis of RXTE‐PCA (Proportional Counter Array) observations of the accretion powered pulsar 4U 1907+09 between 2007 June and 2008 August. 4U 1907+09 had been in a spin‐down episode with a spin‐down rate of −3.54 × 10−14 Hz s−1 before 1999. From RXTE observations after 2001 March, the source showed a ∼60 per cent decrease in spin‐down magnitude, and INTEGRAL observations after 2003 March showed that source started to spin‐up. We found that the source recently entered into a new spin‐down episode with a spin‐down rate of −3.59 × 10−14 Hz s−1. This spin‐down rate is pretty close to the previous long‐term spin‐down rate of the source measured before 1999. From the spectral analysis, we showed that hydrogen column density varies with the orbital phase.

We present analysis of RXTE-PCA observations of GX 1+4 between March 3, 2001 and January 31, 2003 together with the CGRO-BATSE Xray flux and frequency derivative time series between 1991 and 1999. From the timing analysis of RXTE-PCA observations, we are able to phase connect pulse arrival times of the source within two different time intervals and obtain corresponding timing solutions. Using these pulse arrival times, we contribute to long term pulse frequency history of the source. We look for episodic correlations and anti-correlations between torque and X-ray luminosity using CGRO-BATSE X-ray flux and frequency derivative time series and find that correlation state of GX 1+4 seems to change on ∼ 100-200 days long intervals. We estimate torque noise of the source and observe flickering noise ( f −1 ). We achieve to measure the longest observed timescale for a noise process among accretion powered X-ray pulsars by extending the noise estimate for a time scale ranging from 31 days to 44 years. Spectral analysis of individual RXTE-PCA observations indicates a significant correlation between iron line flux and unabsorbed X-ray flux. Pulse phase resolved spectra of the source indicate a broadening of iron line complex at the bin corresponding to the pulse minimum.

We present timing analysis of the accretion powered pulsar SXP 1062, based on the observations of Swift, XMM-Newton and Chandra satellites covering a time span of about 2 years. We obtain a phase coherent timing solution which shows that SXP 1062 has been steadily spinning down with a rate − 4.29(7) × 10 −14 Hz s −1 leading to a surface magnetic field estimate of about 1.5 × 10 14 G. We also resolve the binary orbital motion of the system from X-ray data which confirms an orbital period of 656(2) days. On MJD 56834.5, a sudden change in pulse frequency occurs with ∆ν = 1.28(5) × 10 −6 Hz, which indicates a glitch event. The fractional size of the glitch is ∆ν/ν ∼ 1.37(6) ×10 −3 and SXP 1062 continues to spin-down with a steady rate after the glitch. A short X-ray outburst 25 days prior to the glitch does not alter the spin-down of the source; therefore the glitch should be associated with the internal structure of the neutron star. While glitch events are common for isolated pulsars, the glitch of SXP 1062 is the first confirmation of the observability of this type of events among accretion powered pulsars. Furthermore, the value of the fractional change of pulse frequency ensures that we discover the largest glitch reported up to now.

Using RXTE, Chandra, XMM-Newton and Swift observations, we for the first time construct the power spectra and torque noise strengths of magnetars.For some of the sources, we measure strong red noise on timescales months to years which might be a consequence of their outbursts. We compare noise strengths of magnetars with those of radio pulsars by investigating possible correlations of noise strengths with spin-down rate, magnetic field and age.Using these correlations, we find that magnetar noise strengths are obeying similar trends with radio pulsars. On the contrary, we do not find any correlation between noise strength and X-ray luminosity which was seen in accretion powered pulsars. Our findings suggest that the noise behaviour of magnetars resembles that of radio pulsars but they possess higher noise levels likely due to their stronger magnetic fields.

We analyse observations of the accretion‐powered pulsar 4U 1907+09 from the International Gamma‐Ray Astrophysics Laboratory (INTEGRAL; between 2005 October and 2007 November) and from the Rossi X‐ray Timing Explorer (RXTE; between 2007 June and 2011 March). Using observations from the Imager on‐board the INTEGRAL satellite (IBIS), the INTEGRAL Soft Gamma‐Ray Imager (ISGRI) and the RXTE Proportional Counter Array (PCA), we update the pulse period history of the source. We construct power spectrum density of pulse frequencies, and we find that fluctuations in the pulse frequency derivatives are consistent with the random walk model with a noise strength of 1.27 × 10−21 Hz s−2. From the X‐ray spectral analysis of RXTE/PCA observations, we find that the hydrogen column density is variable over the binary orbit, and that it tends to increase just after the periastron passage. We also show that the X‐ray spectrum becomes hardened with decreasing X‐ray flux. We discuss the pulse‐to‐pulse variability of the source near dipping ingress and egress. We find that the source is more likely to undergo dipping states after apastron until periastron when the accretion from clumpy wind might dominate. Thus, occasional transitions to a temporary propeller state might occur.