Radiation pressure and pulsation effects on the Roche lobeT. Dermine1, A. Jorissen1, L. Siess1, and A. Frankowski2
1 Institut d'Astronomie et d'Astrophysique, Université libre de Bruxelles, Faculté des Sciences, CP 226, Boulevard du Triomphe, 1050 Bruxelles, Belgium
2 Department of Physics, Technion-Israel Institute of Technology, 32000 Haifa, Israel
Received 9 April 2009 / Accepted 15 August 2009
Context. Several observational pieces of evidence indicate that specific evolutionary channels that involve Roche lobe overflow are not correctly accounted for by the classical Roche model.
Aims. We generalise the concept of the Roche lobe in the presence of extra forces (caused by radiation pressure or pulsations). By computing the distortion of the equipotential surfaces, we are able to evaluate the impact of these perturbing forces on the stability of Roche lobe overflow (RLOF).
Methods. Radiative forces are parametrised through the constant reduction factor that they impose on the gravitational force from the radiating star (neglecting any shielding in the case of high optical thickness). Forces imparted by pulsation are derived from the velocity profile of the wind that they trigger.
Results. We provide analytical expressions to compute the generalised Roche radius. Depending on the extra force, the Roche lobe radius may either stay unchanged, become smaller, or even become meaningless (in the presence of a radiatively- or pulsation-driven wind). There is little impact on the RLOF stability.
Key words: stars: binaries: general -- stars: mass-loss -- stars: winds, outflows
© ESO 2009