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Models of the formation, evolution and photoevaporation of circumstellar disks are an essential ingredient in many theories of the formation of planetary systems. The ratio of disk mass over stellar mass in the circumstellar phase of a disk…

Solar and Stellar Astrophysics · Physics 2015-05-18 R. Visser , C. P. Dullemond

We consider the behavior of matter in the accretion column that emerges under accretion in binary systems near the surface of a white dwarf. The plasma heated in a standing shock wave near the white dwarf surface efficiently radiates in the…

High Energy Astrophysical Phenomena · Physics 2013-12-18 Andrey Semena , Mikhail Revnivtsev

We have performed fully 3D simulations of the collapse of molecular cloud cores which obey the logatropic equation of state. By following the collapse of these cores from states of near hydrodynamic equilibrium, we are able to produce…

Astrophysics · Physics 2007-05-23 M. A. Reid , R. E. Pudritz , J. Wadsley

The pulsed X-ray emission from the neutron star surface acts as a window to study the state of matter in the neutron star interior. For accreting millisecond pulsars, the surface X-ray emission is generated from the `hotspots' formed due to…

High Energy Astrophysical Phenomena · Physics 2025-05-20 Pushpita Das , Tuomo Salmi , Jordy Davelaar , Oliver Porth , Anna Watts

Models and observations indicate that the impact of matter accreting onto the surface of young stars produces regions at the base of accretion columns, in which optically thin and thick plasma components coexist. Thus an accurate…

Disk accretion to rotating stars with complex magnetic fields is investigated using full three-dimensional magnetohydrodynamic (MHD) simulations. The studied magnetic configurations include superpositions of misaligned dipole and quadrupole…

Astrophysics · Physics 2009-11-13 M. Long , M. M. Romanova , R. V. E. Lovelace

Using two-dimensional (2D) and three-dimensional (3D) kinetic simulations, we examine the impact of simulation dimensionality on the laser-driven electron acceleration and the emission of collimated $\gamma$-ray beams from hollow…

Plasma Physics · Physics 2021-10-27 Tao Wang , David Blackman , Katherine Chin , Alexey Arefiev

In this review, I summarize the main X-ray/hard X-ray properties of the accretion flows around black holes and neutron stars based on recent broad-band spectral and timing observations performed by the BeppoSAX and Rossi X-ray Timing…

Astrophysics · Physics 2009-11-10 Didier Barret

Studying the physical processes occurring in the region just above the magnetic poles of strongly magnetized, accreting binary neutron stars is essential to our understanding of stellar and binary system evolution. Perhaps more importantly,…

Here we present the results from two sets of simulations, in two and three spatial dimensions. In two dimensions, the simulations include multifrequency flux-limited diffusion neutrino transport in the "ray-by-ray-plus" approximation,…

Astrophysics · Physics 2009-11-13 A. Mezzacappa , S. W. Bruenn , J. M. Blondin , W. R. Hix , O. E. B. Messer

The nonlinear regime of laser-plasma interaction including both two-plasmon--decay (TPD) and stimulated Raman scattering (SRS) instabilities has been studied in three-dimensional (3-D) particle-in-cell simulations with parameters relevant…

Plasma Physics · Physics 2019-10-09 H. Wen , A. V. Maximov , R. Yan , J. Li , C. Ren , F. S. Tsung

A two dimensional numerical model in the axisymmetric approximation that describes the flow structure in the magnetosphere of the white dwarf in the EX Hya system has been developed. Results of simulations show that the accretion in EX Hya…

Solar and Stellar Astrophysics · Physics 2019-12-23 P. B. Isakova , A. G. Zhilkin , D. V. Bisikalo , A. N. Semena , M. G. Revnivtsev

Accretion-powered X-ray pulsars are among the most luminous X-ray sources in the Galaxy. However, despite decades of theoretical and observational work since their discovery, no satisfactory model for the formation of the observed X-ray…

Astrophysics · Physics 2009-11-11 Peter A. Becker , Michael T. Wolff

Accretion disks are three-dimensional, turbulent, often self-gravitating, magnetohydrodynamic flows, which can be modeled in detail with numerical simulations. In this paper, we present a new algorithm that is based on a spectral…

Astrophysics · Physics 2009-07-22 Chi-kwan Chan , Dimitrios Psaltis , Feryal Ozel

Direct measurements of cosmic ray (CR) species combined with observations of their associated gamma-ray emissions can be used to constrain models of CR propagation, trace the structure of the Galaxy, and search for signatures of new…

High Energy Astrophysical Phenomena · Physics 2018-04-11 Gudlaugur Johannesson , Troy A. Porter , Igor V. Moskalenko

We consider the production of 2.22 MeV radiation resulting from the capture of neutrons in the atmosphere of the secondary in an X-ray binary system, where the neutrons are produced in the accretion disk around the compact primary star and…

Astrophysics · Physics 2009-11-07 P. Jean , N. Guessoum

The luminosity of X-ray pulsars powered by accretion onto magnetized neutron stars covers a wide range over a few orders of magnitude. The brightest X-ray pulsars recently discovered as pulsating ultraluminous X-ray sources reach accretion…

High Energy Astrophysical Phenomena · Physics 2019-05-29 Alexander A. Mushtukov , Igor S. Ognev , Dmitrij I. Nagirner

This dissertation is written as an annotated collection of selected articles. The dissertation focuses on the modelling of accretion disks in X-ray binaries with a black hole or neutron star. The main objective is to use advanced numerical…

High Energy Astrophysical Phenomena · Physics 2023-10-23 Debora Lančová

Azimuthal structures emerging in beam-generated partially magnetized plasmas are investigated using three-dimensional particle-in-cell/Monte Carlo collision simulations. Two distinct instability regimes are identified at low pressures. When…

Plasma Physics · Physics 2025-07-01 Jian Chen , Andrew T. Powis , Igor D. Kaganovich , Zhibin Wang

We present a 3-D ideal MHD simulation of magnetospheric accretion onto a non-rotating star. The accretion process unfolds with intricate 3-D structures driven by various mechanisms. First, the disc develops filaments at the magnetospheric…

Solar and Stellar Astrophysics · Physics 2023-12-18 Zhaohuan Zhu , James M. Stone , Nuria Calvet