Over niet-conservatieve evolutie van dubbelsterren

Abstract

We investigate the possible non-conservatism of binary star evolution. During a short, intense phase of Roche Lobe Overflow (RLOF), it is possible for the gainer to be incapable of accreting all matter lost by the donor. The enhanced rotational velocity caused by spin-up of the gainer may combine with the accretion luminosity, resulting from the concentration of the RLOF-material in an equatorial hot spot, to drive matter from the system and into the interstellar medium. Whether or not a non-conservative phase will develop depends on the initial parameters of the system, i.e. the primary mass, mass ratio and orbital period. A phase of non-conservative RLOF results in longer durations of high ratios q of donor to gainer mass. The mechanism may thus help to better explain the observed Algol mass ratio distribution, whereas conservative simulations result in too little high q-values. As material is expelled through a sort of enhanced stellar wind, non-conservatism barely affects the orbital period distribution, which is already retrieved satisfactorily through conservative evolution. The presented scenario thus better explains the observed mass ratio and orbital period distribution than does conservative binary evolution.

Date of Award	6 Jul 2007
Original language	Dutch
Supervisor	Walter Van Rensbergen (Promotor)