Related papers: Constraints on Torque-Reversing Accretion-Powered …

In the beginning of 2023 the Be transient X-ray pulsar RX J0440.9+4431 underwent a fist-ever giant outburst observed from the source peaking in the beginning of February and reaching peak luminosity of $\sim 4.3\times10^{37}$ erg s$^{-1}$.…

We observed the anomalous X-ray pulsar 4U 0142+61 using the Proportional Counter Array (PCA) aboard the Rossi X-ray Timing Explorer (RXTE) in March 1996. The pulse frequency was measured as f = 0.11510039(3) Hz with an upper limit of df/dt…

Quasi-spherical accretion in wind-fed X-ray pulsars is discussed. At X-ray luminosities <4 10^{36} erg/s, a hot convective shell is formed around the neutron star magnetosphere, and subsonic settling accretion regime sets in. In this…

We report on the long-term evolution of the spin period of the symbiotic X-ray pulsar GX 1+4 and a possible interpretation within a model of quasi-spherical accretion. New period measurements from BeppoSAX/WFC, INTEGRAL/ISGRI and Fermi/GBM…

Neutron stars in close binary systems have the potential to spin up to millisecond periods due to the accretion of matter and angular momentum from their low-mass companions. In later stages of this process, they sometimes start to swing…

Accreting millisecond X-ray pulsars (AMXPs) are transient X-ray sources likely to be in the final evolutionary phases of low-mass X-ray binaries (LMXBs). In this work, we have investigated the torque and X-ray luminosity variations of five…

We report on 10 yr of monitoring of the 8.7-s Anomalous X-ray Pulsar 4U 0142+61 using the Rossi X-Ray Timing Explorer (RXTE). This pulsar exhibited stable rotation from 2000 until February 2006: the RMS phase residual for a spin-down model…

With the ever-increasing sensitivity and timing baselines of modern radio telescopes, a growing number of pulsars are being shown to exhibit transitions in their rotational and radio emission properties. In many of these cases, the two are…

We have investigated the detailed torque-reversal behavior of 4U 1626--67 in the framework of the recently developed comprehensive model of the inner disk radius and torque calculations for neutron stars accreting from geometrically thin…

In this paper we address the question of why the observed periods of the Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray Repeaters (SGRs) are clustered in the range 2-12 s. We explore a possibility to answer this question assuming that…

Possible manifestations of accreting magnetars are discussed. It is shown that the four ultra-luminous X-ray pulsars can be understood in the accreting low magnetic field magnetar scenario. The NGC300 ULX1 pulsar may have a higher dipole…

RXTE observations of the X-ray transient pulsar 2S 1417-62 between 1999 November and 2000 August with a total exposure of $\sim 394$ ksec were analyzed. Observations include a main outburst followed by a series of mini outbursts. Changes in…

We present temporal and spectral properties of a unique X-ray dip in GX 301-2 as seen with Rossi X-ray Timing Explorer in May 2010. The X-ray pulsation from the source gradually declined prior to the dip, disappears for one spin cycle…

RX J0440.9+4431 is an accreting X-ray pulsar (XRP) that remained relatively unexplored until recently, when major X-ray outburst activity enabled more in-depth studies. Here, we report on the discovery of ${\sim}0.2$ Hz quasi-periodic…

We report on two years of flux and spin evolution monitoring of 1E 1048.1$-$5937, a 6.5-s X-ray pulsar identified as a magnetar. Using {\it Swift} XRT data, we observed an X-ray outburst consisting of an increase in the persistent 1--10 keV…

Accreting Millisecond X-ray Pulsars like IGR J00291+5934 are important because it is possible to test theories of pulsar formation and evolution. They give also the possibility to constrain gravitational wave emission theories and the…

Using the spin and flux evolution of the accreting pulsar 4U 1626$-$67 across the 2008 torque reversal, we determine the fastness parameter dependence of the dimensionless torque acting on the pulsar. We find that the dimensionless torque…

We report the detection of a sudden spin-up of the 11 s anomalous X-ray pulsar 1RXS J170849.0-4000910 in regular timing observations made with the Rossi X-ray Timing Explorer. The event, which occurred between MJD 51446 (1999 September 25)…

Accreting X-Ray Binaries display a wide range of behaviours. Some of them are observed to spin up steadily, others to alternate between spin-up and spin-down states, sometimes superimposed on a longer trend of either spin up or spin down.…

We present a comprehensive timing and spectral analysis of the HMXB 4U 1538-522 by using the Nuclear Spectroscopic Telescope Array (NuSTAR) observatory data. Using three archived observations made between 2019 and 2021, we have detected…