On the origin of Centaurus X-3 and related binary X-ray sources

Numerical calculations following the evolution of both components of a possible progenitor system (15 solar masses, 5 solar masses, 8.53 days) for Cen X-3 have been carried into the first phase of rapid mass exchange in case B. The calculations indicate that the secondary quickly expands, forcing the system into contact. Shortly after contact, the calculations terminated when the system entered a phase of extremely rapid mass loss through the outer Lagrangian point. For a variety of initial conditions, restricted three-body calculations show that the ejected gas escapes the system entirely and carries off specific angular momentum which, initially, is 10 times the average specific angular momentum. The rapid decrease in separation induced by the loss of angular momentum accelerates the mass loss enormously. This phase could not be followed numerically, but the result is likely to be an enormous loss of mass and decrease in period, probably terminating when the primary is stripped of all mass above its helium core. A similar evolutionary phase in a lower-mass binary (4 solar masses, 1 solar mass, 2 days) could lead to the production of short-period cataclysmic variable stars.