Low- and intermediate-mass close binary evolution and the initial-final mass relation - III. Conservative case with convective overshooting and non-conservative case without overshooting

Abstract

We have completed our series of calculation of case B evolution of Population I close binaries by including a conservative case with convective overshooting and a non-conservative case without convective overshooting in this paper. To apply the results easily to binary population synthesis, we fit two formulae for the remnant mass as a function of the initial mass of the primary, the radius of the primary at the onset of Roche lobe overflow (RLOF) and the initial mass ratio, with errors less than 1.9 per cent and 3.6 per cent for the conservative and non-conservative cases, respectively. We have also made comparisons between the results in this paper and those of previous studies in this series to examine the effects of our assumptions. We find that the remnant mass depends on when RLOF begins in the Hertzsprung gap and the dependence increases with the mass of the primary. Helium-carbon-oxygen white dwarfs are formed in this series of calculation. Both the non-conservative assumption and convective overshooting make RLOF more stable: some binaries with initial mass ratios q (i) = 4.0 are dynamically stable during RLOF in all cases except for the conservative case without overshooting. From these models, we have discussed potential electron-degenerate oxygen-neon cores. Finally, we show the conditions under which one evolution scenario may be more likely than the others according to the results of previous authors.