A Comparative Catalogue of Gravitational and Orbital Time-Dilation Effects in Galactic X-ray Binary Systems

This study presents a comparative catalogue of gravitational and orbital time-dilation effects in 18 well-characterized Galactic X-ray binary systems, including both black-hole and neutron-star binaries. Using published dynamical masses, orbital periods, and distances, we calculate Schwarzschild radii, gravitational time-dilation factors at a fixed altitude above the compact object, and combined relativistic time-dilation effects experienced by donor stars due to orbital motion and gravitational potential. For a subset of black holes with measured spin parameters, we additionally evaluate spin-dependent proper-time deficits at the Kerr innermost stable circular orbit (ISCO). Monte Carlo uncertainty propagation is performed to estimate credible intervals for derived quantities. The results show that donor stars in the most compact systems experience relativistic time lags of several hours per century, while a hypothetical probe located near the most massive black hole in the sample, Cygnus X-1, would experience a gravitational time lag of approximately three years per century relative to a distant observer. The analysis demonstrates the strong influence of orbital compactness and black-hole spin on observable time-dilation effects. This work provides an observationally grounded reference catalogue for relativistic time-dilation effects in Galactic X-ray binaries and may be useful for astrophysical education, outreach, and future studies of relativistic timing and compact-object environments.