Dynamical Effects of Magnetic Opacity in Neutron Star Accretion Columns
arXiv:2307.02410 · doi:10.1093/mnras/stad2043
Abstract
We present relativistic, radiation magnetohydrodynamic simulations of supercritical neutron star accretion columns in Cartesian geometry, including temperature-dependent, polarization-averaged Rosseland mean opacities accounting for classical electron scattering in a magnetic field. Just as in our previous pure Thomson scattering simulations, vertical oscillations of the accretion shock and horizontally propagating entropy waves (photon bubbles) are present in all our simulations. However, at high magnetic fields ~G, the magnetic opacities produce significant differences in the overall structure and dynamics of the column. At fixed accretion rate, increasing the magnetic field strength results in a shorter accretion column, despite the fact that the overall opacity within the column is larger. Moreover, the vertical oscillation amplitude of the column is reduced. Increasing the accretion rate at high magnetic fields restores the height of the column. However, a new, slower instability takes place at these field strengths because they are in a regime where the opacity increases with temperature. This instability causes both the average height of the column and the oscillation amplitude to substantially increase on a time scale of ~ms. We provide physical explanations for these results, and discuss their implications for the observed properties of these columns, including mixed fan-beam/pencil-beam emission patterns caused by the oscillations.
arXiv commentAccepted for publication in MNRAS
References in corpus (21)
- The Athena++ Adaptive Mesh Refinement Framework: Design and Magnetohydrodynamic Solvers
- Spectral Formation in Accreting X-Ray Pulsars: Bimodal Variation of the Cyclotron Energy with Luminosity
- Cyclotron lines in highly magnetized neutron stars
- V0332+53 in the outburst of 2004--2005: luminosity dependence of the cyclotron line and pulse profile
- Ultraluminous X-ray sources
- A reflection model for the cyclotron lines in the spectra of X-ray pulsars
- Photon Bubbles in Accretion Discs
- Completing the puzzle of the 2004-2005 outburst in V0332+53: the brightening phase included
- An Algorithm for Radiation Magnetohydrodynamics Based on Solving the Time-dependent Transfer Equation
- Local Radiative Hydrodynamic and Magnetohydrodynamic Instabilities in Optically Thick Media
- Luminosity dependence of the cyclotron line and evidence for the accretion regime transition in V 0332+53
- An Implicit Finite Volume Scheme to Solve the Time Dependent Radiation Transport Equation Based on Discrete Ordinates
- Giant outburst of EXO 2030+375: pulse-phase resolved analysis of INTEGRAL data
- Detection of Cyclotron Resonance Scattering Feature in High Mass X-ray Binary Pulsar SMC X-2
- Radiative Relativistic Magnetohydrodynamic Simulations of Neutron Star Column Accretion in Cartesian Geometry
- Spectral and Timing Analysis of the accretion-powered pulsar 4U 1626-67 observed with Suzaku and NuSTAR
- Accreting strongly magnetised neutron stars: X-ray Pulsars
- Firm Detection of a Cyclotron Resonance Feature with Suzaku in the X-ray Spectrum of GRO J1008-57 during a Giant Outburst in 2012
- Dynamics of Neutron Star Accretion Columns in Split-Monopole Magnetic Fields
- Radiative MHD Simulations of Photon Bubbles in Radiation-Supported Magnetized Atmospheres of Neutron Stars with Isotropic Thomson Scattering
- Mean opacities of a strongly magnetized high temperature plasma
Cited by in corpus (3)
- The giant outburst of EXO 2030+375 I: Spectral and pulse profile evolution
- GR-RMHD Simulations of Super-Eddington Accretion Flows onto a Neutron Star with Dipole and Quadrupole Magnetic Fields
- Hydrodynamical simulation of the structure of the X-ray pulsar accretion channel: accounting for resonant scattering