The Galactic 26Al Problem and The Close Binary SNIb/c Solution?

Abstract

The origin of the long-lived radioactive 26Al, which has been observed in the Galactic interstellar medium from its 1.809 MeV decay gamma-ray line emission, has been a persistent problem for over twenty years. Wolf-Rayet (WR) winds were thought to be the most promising source, but their calculated 26Al yields are not consistent with recent analyses of the 1.809 MeV emission from the nearest WR star and nearby OB associations. The expected 26Al yield from the WR star exceeds by as much as a factor of 3, that set by the 2-sigma upper limit on the 1.809 MeV emission, while the WR yields in the OB associations are only about 1/3 of that required by the 1.809 MeV emission. We suggest that a solution to these problems may lie in 26Al from a previously ignored source: explosive nucleosynthesis in the core collapse SNIb/c supernovae of WR stars that have lost most of their mass to close binary companions. Recent nucleosynthetic calculations of SNIb/c suggest that their 26Al yields depend very strongly on the final, pre-supernova mass of the WR star, and that those with final masses around 6 to 8 solar masses are expected to produce as much as 0.01 solar masses of 26Al per supernova. Such binary SNIb/c make up only a small fraction of the current SNIb/c and only about 1% of all Galactic core collapse supernovae. They appear to be such prolific sources that the bulk of the present 26Al in the Galaxy may come from just a few hundred close binary SNIb/c and the intense 1.809 MeV emission from nearby OB associations may come from just one or two such supernova.

Accepted for publication in Astrophysical Journal Letters, 611,10 August 2004

References in corpus (9)

• Nucleosynthesis in Massive Stars With Improved Nuclear and Stellar Physics
• The evolution of rotating stars
• Stellar evolution with rotation X: Wolf-Rayet star populations at solar metallicity
• Explosive Nucleosynthesis in Hypernovae
• 26Al and 60Fe From Supernova Explosions
• The discovery of a low mass, pre-main-sequence stellar association around gamma Velorum
• Gamma-ray line emission from OB associations and young open clusters. II. The Cygnus region
• Fundamental stellar parameters of zeta Pup and gamma^2 Vel from HIPPARCOS data
• 26Al yields from rotating Wolf--Rayet star models

Cited by in corpus (5)

• Characterizing Supernova Progenitors via the Metallicities of their Host Galaxies, from Poor Dwarfs to Rich Spirals
• Al-26 and the formation of the Solar System from a molecular cloud contaminated by Wolf-Rayet winds
• Gamma-Rays from Single Lobe Supernova Explosions
• On the Origin of the Early Solar System Radioactivities. Problems with the AGB and Massive Star Scenarios
• Very massive star winds as sources of the short-lived radioactive isotope ${}^{26}$Al