Mass Loss out of Close Binaries

It has been established that Algols, issuing from a binary with a B-type primary at birth, show more observed systems at large mass ratios than calculated with the conservative assumption, where no mass and angular momentum leaves the system. We have introduced in the Brussels binary evolutionary code the spinning up of the gainer caused by impacting mass coming from the donor star when the latter fills up its Roche volume. This impacting matter creates moreover a hot spot at the area of impact. When the kinetic energy of fast rotation added to the radiative energy of the hot spot is larger than the binding energy, a fraction of the transferred matter leaves the system. Our calculations have been performed on a large number of binaries during hydrogen core burning of the donor (case A) as well as during hydrogen shell burning of the donor (case B). The evolutionary tracks are available as a catalogue at the CDS in Strasbourg. Our calculations show that binaries with a late B-primary at birth evolve almost conservatively, whereas those with an early B-type primary blow matter into the interstellar space during a short lasting era of fast mass transfer. The obtained calculated distribution of mass ratios now fits the observations a little bit better but in order to obtain a satisfying agreement the calculated era of fast mass transfer should last somewhat longer and be somewhat slower. The obtained calculated distribution of orbital periods fits the observations well.