Theoretical Exploration of Mass Transfer Dynamics and High-Energy Emissions in X-Ray Binaries Hosting Red Supergiants

Abstract

X-ray binaries containing red-supergiant companions provide a setting in which stellar-wind mass transfer, magnetic fields, and accretion processes jointly shape high-energy emission. This theoretical study examines the influence of these factors on accretion dynamics and X-ray variability. A model combining hydrodynamic descriptions, magnetohydrodynamic relations, Bondi–Hoyle–Lyttleton accretion, spectral modelling, and smoothed-particle hydrodynamics was formulated to represent the interaction between the red-supergiant wind and the compact object. Seasonal and longitudinal variations were represented through sinusoidal functions of the Earth’s orbital and observational angles. The model indicates periodic changes in X-ray flux and a sinusoidal variation at a fixed longitude of π/4. The simulated flux shows a positive correlation with the observational comparison data, whereas the simulated and observed energy values show an inverse relationship. Magnetic braking produces a rapid increase in the accretion rate within the inner disc, followed by saturation at larger radii, while disc temperature declines with radius. Over 100 years, the model gives an exponential decrease in the accretion rate from 10²⁵ to 10²⁰ kg s⁻¹ and in X-ray flux from 10²⁸ to 10²⁰ erg s⁻¹. Increasing magnetic-field strength also modifies the spectral distribution and enhances the hard X-ray component. The results demonstrate the combined importance of stellar-wind structure, magnetic interaction, disc evolution, and viewing geometry in theoretical descriptions of X-ray binaries with red-supergiant companions.