Driving Mass Out of a Close Binary

It has been reported that the observed distribution of Algol binaries contains more systems with large mass ratios than can be produced by conservative evolution. We developed a code of non-conservative evolution in which during a short, violent phase of Roche lobe overflow, the gainer can be incapable of accreting all matter transferred by the donor. Enhanced rotational velocity caused by spin-up of the gainer combined with accretion luminosity, resulting from the concentration of infalling material in an equatorial hot spot, drives matter from the system. The development of a non-conservative phase depends on the initial parameters of the system. Low mass binaries never achieve high enough mass transfer rates, and hence do not lose mass. In intermediate mass binaries matter will be blown away by the gainer during the short era of rapid Roche lobe overflow, before or at the start of the Algol phase. We have calculated the evolution of binaries over a wide range of initial donor masses, orbital periods and mass ratios. We present the results for the cases where mass transfer starts during core hydrogen burning of the donor and find systems with non-conservatism during which approximately half of the transferred mass is blown into the interstellar medium. Finally, we present the comparison of the observed mass ratio distribution of Algols with the new results.