Evolution of Low Mass Binaries under the Influence of Gravitational Radiation

Extract

Evolutionary changes of masses and periods under the influence of gravitational radiation (GR) are computed for binaries with main-sequence or degenerate hydrogen-helium (H), helium (He) and carbon (C) secondaries. Tracks in the P-M₂ and P-M₂ planes are determined. The orbital period of systems P with a non-degenerate dwarf filling its Roche lobe decreases until the time-scale of GR (~ 10⁹−10¹⁰yrs) becomes shorter than the thermal time-scale τ_KH of the mass losing component M₂. When M₂ becomes ~ 0.1 M_⊙, P begins to increase. This could account for the existence of the minimal P ≈ 1.3^h and for the accumulation of observed cataclysmic binaries (CB) below P ≤ 2^h. The GR can be the driving force for evolution of cataclysmic binaries: TT Ari, OY Car, Z Cha, and WZ Sge as their P, M₂ and indicate. The rate of mass exchange driven by GR is ~ 10⁻⁹−10⁻¹⁰ M_⊙/yrs. It is enough to feed the X-ray bursters and related objects.