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We discuss results of global 3D MHD simulations of accretion on to a rotating magnetized star with a tilted dipole magnetic field, where the accretion is driven by the magneto-rotational instability (MRI). The simulations show that…

Solar and Stellar Astrophysics · Physics 2015-06-03 M. M. Romanova , G. V. Ustyugova , A. V. Koldoba , R. V. E. Lovelace

We present results of fully three-dimensional MHD simulations of disk accretion to a rotating magnetized star with its dipole moment inclined at an angle Theta to the rotation axis of the disk. We observed that matter accretes from the disk…

The inner region of the accretion disk around a magnetized star (T Tauri star, white dwarf or neutron star) is subjected to magnetic torques that induce warping and precession of the disk. These torques arise from the interaction between…

Astrophysics · Physics 2009-11-10 Harald P. Pfeiffer , Dong Lai

We report results from calculations investigating stationary magnetic field configurations in accretion discs around magnetised neutron stars. Our strategy is to start with a very simple model and then progressively improve it providing…

Solar and Stellar Astrophysics · Physics 2014-11-20 L. Naso , J. C. Miller

We explore the possibility to explain the properties of the Be/X-ray pulsars observed in the Small Magellanic Cloud within the magnetic levitation accretion scenario. This implies that their X-ray emission is powered by a wind-fed accretion…

High Energy Astrophysical Phenomena · Physics 2016-11-23 N. R. Ikhsanov , S. Mereghetti

We present analytic calculations of the electromagnetic torques acting on a magnetic neutron star rotating in vacuum, including near-zone torques associated with the inertia of dipole and quadrupole magnetic fields. We incorporate these…

Solar and Stellar Astrophysics · Physics 2015-06-12 J. J. Zanazzi , Dong Lai

We assess the modification of angular momentum transport in various configurations of star-disk accreting systems based on numerical simulations with different parameters. We quantify the torques exerted on a star by the various components…

Solar and Stellar Astrophysics · Physics 2023-11-01 M. Čemeljić , A. S. Brun

We consider a simple scenario for the accretion of matter onto a neutron star in order to understand processes in the inner pulsar magnetosphere during the transition stage between different accretion modes. A simple quasi-spherical…

High Energy Astrophysical Phenomena · Physics 2016-02-12 W. Bednarek , P. Banasinski

We examine how accretion on to T Tauri stars may be modulated by a time-dependent `magnetic gate' where the inner edge of the accretion disc is disrupted by a varying stellar field. We show that magnetic field variations on time-scales…

Astrophysics · Physics 2015-06-24 C. J. Clarke , P. J. Armitage , K. W. Smith , J. E. Pringle

Disc accretion to a rotating star with a non-dipole magnetic field is investigated for the first time in full three-dimensional (3D) magnetohydrodynamic (MHD) simulations. We investigated the cases of (1) pure dipole, (2) pure quadrupole,…

Astrophysics · Physics 2008-11-26 M. Long , M. M. Romanova , R. V. E. Lovelace

Influences of the mass, moment of inertia, rotation, absence of stability in the atmosphere and some other parameters of neutron stars on the evolution of pulsars are examined. It is shown that the locations and evolutions of soft gamma…

Astrophysics · Physics 2009-11-10 Oktay H. Guseinov , Askin Ankay , Sevinc O. Tagieva

Simulations and analytic arguments suggest that the turbulence driven by magnetorotational instability (MRI) in accretion discs can amplify the toroidal (azimuthal) component of the magnetic field to a point at which magnetic pressure…

Astrophysics · Physics 2008-11-26 M. C. Begelman , J. E. Pringle

We study the stability of poloidal magnetic fields anchored in a thin accretion disc. The two-dimensional hydrodynamics in the disc plane is followed by a grid-based numerical simulation including the vertically integrated magnetic forces.…

Astrophysics · Physics 2015-06-24 R. Stehle , H. C. Spruit

How the accreted mass settling on the surface of a neutron star affects the topology of the magnetic field and how the secular evolution of the binary system depends on the magnetic field change is still an open issue. We report evidence…

High Energy Astrophysical Phenomena · Physics 2016-07-13 G. Cusumano , V. La Parola , A. D'Ai , A. Segreto , G. Tagliaferri , S. D. Barthelmy , N. Gehrels

Significant research in compact stars is currently focused on two kinds of enigmatic sources: anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs). Although AXPs and SGRs are popularly thought to be magnetars, other models…

High Energy Astrophysical Phenomena · Physics 2015-05-20 H. Tong , L. M. Song , R. X. Xu

The solid material of protoplanetary discs forms an asymmetric pattern around a low-mass planet (M_p<=10M_Earth) due to the combined effect of dust-gas interaction and the gravitational attraction of the planet. Recently, it has been shown…

Earth and Planetary Astrophysics · Physics 2020-09-09 Zsolt Regály

We propose a new model for these QPOs based on forced oscillations induced in the accretion disk due to the stellar magnetic field. First, it is shown that a magnetized accretion disk evolving in a rotating nonaxisymmetric magnetic field…

Astrophysics · Physics 2016-08-30 J. Pétri

A newly born millisecond magnetar has been proposed as one possible central engine of some long gamma-ray bursts (LGRBs) with X-ray plateau. In this work, we used a universal correlation between initial spin period ($P_0$) and surface…

High Energy Astrophysical Phenomena · Physics 2026-01-01 Lin Lan , He Gao , Litao Zhao , Shunke Ai , Jie Lin , Long Li , Lang Xie , Li-Ping Xin , Jian-Yan Wei

We present our findings from the first long X-ray observation of the hard X-ray source Swift J0826.2-7033 with XMM-Newton, which has shown characteristics of magnetic accretion. The system appears to have a long orbital period (~7.8 h)…

High Energy Astrophysical Phenomena · Physics 2024-11-20 Nikita Rawat , Domitilla De Martino , Koji Mukai , Maurizio Falanga , Nicola Masetti , Jeewan C. Pandey

X-ray observations of the tidal disruption event (TDE) candidate AT 2019avd show drastic variabilities in flux and spectral shape over hundreds of days, providing clues on the accretion disc-corona evolution. We utilize a disc-corona model,…

High Energy Astrophysical Phenomena · Physics 2026-03-27 Haichao Xu , Xinwu Cao , Yanan Wang , Andrzej A. Zdziarski