Binaries and Supernovae of Type I

It is suggested that the immediate progenitors of Type I supernovae in elliptical galaxies are binary systems of long period (1-6 years) that have evolved from an initial configuration consisting of a light secondary of mass less than or equal to 0.8 M0 and a primary of intermediate mass (1.8-3 M0), with orbital period between 5 and 9 years. Beginning on the main sequence, the primary evolves rapidly and, following mass loss and/or mass transfer, becomes a carbon-oxygen white dwarf of mass close to 1.4 M0. The secondary, now of mass 0.8 M0, evolves for 1010 years before reaching the asymptotic giant branch. On swelling beyond its Roche surface, the secondary transfers mass onto the primary which then (we presume) develops rapidly into a supernova. An examination of the frequency of binary systems with appropriate orbital characteristics shows that our conjecture is not inconsistent with the available data concerning the frequency of Type I supernovae. Subject headings: biiaan.es - mass loss - supernovae