Related papers: Constraints on the magnetic field structure in acc…
We analyse RXTE/PCA X-ray spectra of the binary X-ray pulsar Her X-1/HZ Her during short high state and one binary orbit in the preceding low state, just before short high turn-on. The spectrum is well described by two continuum components…
We report the discovery of scaling in the mesoscale magnetic microstructure of bulk ferromagnets. Supported by analytical micromagnetic theory, we introduce the field-dependent scaling length $l_{\mathrm{C}}(H)$, which describes the…
Millisecond x-ray pulsars have weak magnetic dipole moments of $\sim 10^{16}$\,T\,m$^3$ compared to ordinary X-ray pulsars with dipole moments of $10^{20}$\,T\,m$^3$. For this reason a surrounding accretion disc can extend closer to the…
We present results from the major coordinated X-ray observing program on the ULX NGC 1313 X-1 performed in 2017, combining $XMM$-$Newton$, $Chandra$ and $NuSTAR$, focusing on the evolution of the broadband ($\sim$0.3-30.0 keV) continuum…
The magnetospheres of accreting neutron stars develop electrostatic gaps with huge potential drops. Protons and ions, accelerated in these gaps along the dipolar magnetic field lines to energies greater than 100 TeV, can impact onto a…
We present an analysis of several high-resolution Chandra grating observations of the X-ray binary pulsar Her X-1. With a total exposure of 170 ks, the observations are separated by years and cover three combinations of orbital and…
Three high-mass X-ray binaries have been discovered recently exhibiting enormous spinup rates. Conventional accretion theory predicts extremely high surface dipolar magnetic fields that we believe are unphysical. Instead, we propose quite…
Strong stellar winds are an important feature in wind-accreting high-mass X-ray binary (HMXB) systems, providing insights into stellar evolution and their impact on surrounding environments. However, the long-term evolution and temporal…
The accreting X-ray pulsar Her X-1 shows two types of long-term variations, both with a period of 35 days: 1) A modulation of the flux with a ten day long Main-On and a 5 d long Short-On, separated by two Off-states, and 2) A systematic…
Recently, ultraluminous X-ray source (ULX) M82 X-2 has been identified to be an accreting neutron star, which has a $P=1.37$ s spin period, and is spinning up at a rate $\dot{P}=-2.0\times 10^{-10}~\rm s\,s^{-1}$. Interestingly, its…
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.…
In order to provide an explanation for the unexpected radial brightness distribution of the steady accretion discs seen in nova-like variables, Nixon & Pringle (2019) proposed that the accretion energy is redistributed outwards by means of…
Pulsating ultra-luminous X-ray sources (PULXs) are characterised by an extremely large luminosity ($ > 10^{40} \text{erg s}^{-1}$). While there is a general consensus that they host an accreting, magnetized neutron star (NS), the problem of…
Accretion disks are ubiquitous in the universe and it is generally accepted that magnetic fields play a pivotal role in accretion-disk physics. The spin history of millisecond pulsars, which are usually classified as magnetized neutron…
We search the literature for reports on the spectral properties of neutron-star low-mass X-ray binaries when they have accretion luminosities between 1E34 and 1E36 ergs/s. We found that in this luminosity range the photon index (obtained…
The strong magnetic field of neutron stars is intimately coupled to the observed temperature and spectral properties, as well as to the observed timing properties (distribution of spin periods and period derivatives). Thus, a proper…
We have considered the existence of neutron star magnetic field given by the cyclotron lines. We collected the data of 9 sources of high-mass X-ray binaries with supergiant companions as a case of testing our model, to demonstrate their…
The dramatic discovery with the Rossi X-Ray Timing Explorer satellite of remarkably coherent $\sim$300--1200 Hz oscillations in the X-ray brightness of some sixteen neutron stars in low-mass binary systems has spurred theoretical modeling…
Magnetic fields of strongly magnetized stars can trap conducting matter due to frozen-in condition. In the force-free regime, the motion of the matter along the field lines may be considered in the "bead on a wire" approximation. Such a…
An accretion disk around a rotating magnetized star is subjected to magnetic torques which induce disk warping and precession. These torques arise from interactions between the stellar field and the induced surface currents on the disk.…