The evolution of a star of initial mass 9 M _ { \odot } , and metallicity Z = 0.02 in a Close Binary System ( CBS ) is followed in the presence of different mass companions in order to study their influence on the final evolutionary stages and , in particular , on the structure and composition of the remnant components .
In order to do that , we study two extreme cases .
In the first one the mass of the secondary is 8 M _ { \odot } , whereas in the second one the mass was assumed to be 1 M _ { \odot } .
For the first of those cases we have also explored the possible outcomes of both conservative and non-conservative mass-loss episodes .
During the first mass transfer episode , several differences arise between the models .
The system with the more extreme mass ratio ( q = 0.1 ) is not able to survive the first Roche lobe overflow ( RLOF ) as a binary , but instead , spiral-in of the secondary onto the envelope of the primary star is most likely .
The system formed by two stars of comparable mass undergoes two mass transfer episodes in which the primary is the donor .
We have performed two sets of calculations corresponding to this case in order to account for conservative and non-conservative mass transfer during the first mass loss episode .
One of our main results is that for the non-conservative case the secondary becomes a Super–AGB star in a binary system .
Such a star undergoes a final dredge-up episode , similar to that of a single star of comparable mass .
The primary components do not undergo a Super–AGB phase , but instead a carbon-oxygen white dwarf is formed in both cases ( conservative and non-conservative ) , before reversal mass transfer occurs .
However , given the extreme mass ratios at this stage between the components of the binary system , especially for the conservative case , the possibility of merger episodes remains likely .
We also discuss the presumable final outcomes of the system and possible observational counterparts .