We follow the evolution of helium stars of initial mass ( 2.2 - 2.5 ) M _ { \odot } , and show that they undergo off-center carbon burning , which leaves behind { \mathbf { \sim } 0.01 M _ { \odot } } of unburnt carbon in the inner part of the core .
When the carbon-oxygen core grows to Chandrasekhar mass , the amount of left-over carbon is sufficient to ignite thermonuclear runaway .
At the moment of explosion , the star will possess an envelope of several 0.1 M _ { \odot } , consisting of He , C , and possibly some H , perhaps producing a kind of peculiar SN .
Based on the results of for accreting white dwarfs , we expect to get thermonuclear runaway at a broad range of \rho _ { c } \approx ( 1 - 6 ) \times 10 ^ { 9 } \mathrm { g cm ^ { -3 } } , depending on the amount of residual carbon .
We verified the feasibility of this scenario by showing that in a close binary system with initial masses ( 8.5 + 7.7 ) M _ { \odot } and initial period of 150 day the primary produces a helium remnant of 2.3 M _ { \odot } that evolves further like the model we considered .