Tidal mass transfer in elliptical-orbit binary stars

Layton, Jeffrey T.; Blondin, John M.; Owen, Michael P.; Stevens, Ian R.

Published in: NewA, 3, 111


High mass X-ray binary star systems with elliptical orbits, like GX 301-2, often exhibit a peak in X-ray luminosity associated with periastron passage. We use a two dimensional hydrodynamics code to examine the possibility that these X-ray flares result from tidal stripping of gas from the primary star, and subsequent accretion of this gas onto the compact companion. We find that if the primary star is rotating near corotation with the orbiting compact companion at periastron, tidally stripped gas can accrete, causing X-ray flares. Such a tidally induced flare will occur substantially after periastron, at a phase of ~0.2 for the parameters used in our model. This flare is characterized by a brief disk accretion phase with a large angular momentum accretion rate. However, in our particular model this disk accretion phase was followed by an equally brief phase of accretion with the opposite sign of angular momentum, resulting in no long-term spin up of the X-ray pulsar.