Supplementary material for PhD thesis "SPH simulations of X-ray binary systems"
This collection comprises the files contained on a CD-ROM which was attached to the thesis when it was submitted in 2006. It was uploaded to ORDO in 2024 for preservation purposes. For more information, please refer to the thesis SPH simulations of X-ray binary systems via ORO.
Thesis abstract
In low mass X-ray binaries a neutron star or a black hole accretes from a low mass companion star via an accretion disc. The physics of accretion discs in these systems is currently an area of vigorous international research activity. In particular the advent of supercomputing has allowed quantitative numerical work on the dynamics of such systems. The numerical simulations are becoming increasingly able to reproduce observed phenomena, and the interplay between simulation and observation is refining the picture derived from analytical work on these systems. Consequently this PhD exploits the synergy between observation and simulation. We present two/three-dimensional smoothed particle hydrodynamics (SPH) simulations of a number of binary systems, such as XTE J1118+480, and reveal complex accretion discs that are continuously varying in shape, kinematics and dissipation. The stream-disc impact region and disc spiral density waves are prominent sources of energy dissipation. For extreme mass ratios the dissipated energy is modulated on the superhump period. We generate synthetic trailed spectrograms that reveal two distinct `S-wave' features, produced by the stream gas and the disc gas at the stream-disc impact shock. These S-waves are non-sinusoidal, and evolve with disc precession phase. We also describe three-dimensional SPH calculations of warped accretion discs in X-ray binary systems. Geometrically thin, optically thick accretion discs are illuminated by a central radiation source. This illumination exerts a non-axisymmetric radiation pressure on the surface of the disc resulting in a torque that acts on the disc to induce a twist or warp. Initially planar discs are shown to be unstable to warping driven by the radiation torque and in general the warps also precess in a retrograde direction relative to the orbital flow. We simulate a number of X-ray binary systems which have different mass ratios using a number of different luminosities for each. Models for X-ray binary systems such as Her X-1 and SS 433 are able to reproduce their observed long period photometric modulations.
