Low- and intermediate-mass close binary evolution and the initial-final mass relation

Using Eggleton's stellar evolution code, we carry out 150 runs of Populatio n I binary evolution calculations with the initial primary mass between 1 a nd 8 M-circle dot, the initial mass ratio q = M-1/M-2 between 1.1 and 4, an d the onset of Roche lobe overflow (RLOF) at an early, middle or late Hertz sprung-gap stage. We assume that PLOP is conservative in the calculations, and find that the remnant mass of the primary may change by more than 40 pe r cent over the range of initial mass ratio or orbital period, for a given primary mass. This is contrary to the often-held belief that the remnant ma ss depends only on the progenitor mass if mass transfer begins in the Hertz sprung gap. We fit a formula, with an error less than 3.6 per cent, for the remnant (white dwarf) mass as a function of the initial mass M-li of the p rimary, the initial mass ratio q(i) and the radius of the primary at the on set of RLOF We also find that a carbon-oxygen white dwarf with mass as low as 0.33 M-circle dot may be formed if the initial mass of the primary is ar ound 2.5 M-circle dot.