The many observations of the emission of a 1.809 MeV -ray line from the galactic disk (see Prantzos & Diehl 1996 for a recent review) provide ample evidence that it contains about of recently synthesized ( y). In addition, a wealth of observations demonstrate that has decayed in situ in some meteoritic inclusions of solar origin (as reviewed by MacPherson et al. 1995), or in various meteoritic grains of likely circumstellar origin (see Anders & Zinner 1993).
These astronomical and cosmochemical observations clearly raise, among many others, the question of the nucleosynthetic origin of . As reviewed by Prantzos & Diehl (1996), asymptotic giant branch stars, Wolf-Rayet (WR) stars, novae, supernovae, and spallation reactions in interstellar clouds have been envisioned.
This paper aims at revisiting the yields based on models for WR stars that account better than previous ones for many observable properties of this type of stars, like their luminosities, surface chemical compositions, or statistics in regions of constant star formation rate, as well as in starburst locations. This improved agreement is obtained through progress made recently in our knowledge of several key physical ingredients, like the opacities, mass loss rates, or nuclear reaction rates. These revised stellar models are described in Sect. 2. The resulting yields from individual model stars are presented in Sects. 3, while the global contribution of the WR stars to the galactic is estimated in Sect. 4. Conclusions are drawn in Sect. 5.
© European Southern Observatory (ESO) 1997
Online publication: June 30, 1998