On the Formation of O-Ne White Dwarfs in Metal-rich Close Binary Systems

The evolution of primary components of initially close binary systems has been followed assuming specific initial conditions such as to have the formation of an O-Ne white dwarf at the end of a nonconservative evolution of the system parameters. More specifically, the evolution of a 10.5 M ○. , Z=Z ○. , and Y=0.27 star model has been traced through the two major episodes of mass transfer in order to make a direct comparison with the previous computations of Iben & Tutukov, which we reproduce quite well. In this case, mass transfer finishes at the beginning of the C-burning phase. Analogous experiments have been performed with both a 10 M ○. and a 10.5 M ○. (Z=2×Z ○. and Y=0.32) star models. In these cases, the second mass-transfer episode continues also during the carbon-burning phase