Wolf–rayet Stars and Radioisotope Production

Radioisotopes are natural clocks which can be used to estimate the age of the solar system and of the Universe (see e.g. Takahashi 1998; Chen & Tilton 1976; see also the recent review by Arnould & Takahashi 1999). They are responsible for the steady decline of the light curves of supernovae (see e.g. Diehl & Timmes 1998, and references therein). The diffuse emission at 1.8 MeV from the decay of Al (e.g. Arnould & Prantzos for a recent review) may also provide a measure of the present day nucleosynthetic activity in our Galaxy. Therefore, even if radionuclides represent only a tiny fraction of the cosmic matter, they carry unique pieces of information. A great number of radioisotopes are produced by massive stars at the time of the supernova explosion. A fraction of them are also produced during the previous hydrostatic burning phases. These nuclides are then ejected either at the time of the supernova event, or through stellar winds during the hydrostatic burning phases. This paper focusses on the non-explosive ejection of radionuclides by Wolf-Rayet (W–R) stars.