Type Ia supernovae ( SNe Ia ) are manifestations of stars deficient of hydrogen and helium disrupting in a thermonuclear runaway .
While explosions of carbon-oxygen white dwarfs are thought to account for the majority of events , part of the observed diversity may be due to varied progenitor channels .
We demonstrate that helium stars with masses between \sim 1.8 and 2.5 \mathrm { M _ { \odot } } may evolve into highly degenerate , near-Chandrasekhar mass cores with helium-free envelopes that subsequently ignite carbon and oxygen explosively at densities \sim ( 1.8 - 5.9 ) \times 10 ^ { 9 } \mathrm { g cm ^ { -3 } } .
This happens either due to core growth from shell burning ( when the core has a hybrid CO/NeO composition ) , or following ignition of residual carbon triggered by exothermic electron captures on \mathrm { { { } ^ { 24 } } Mg } ( for a NeOMg-dominated composition ) .
We argue that the resulting thermonuclear runaways is likely to prevent core collapse , leading to the complete disruption of the star .
The available nuclear energy at the onset of explosive oxygen burning suffices to create ejecta with a kinetic energy of \sim 10 ^ { 51 } erg , as in typical SNe Ia .
Conversely , if these runaways result in partial disruptions , the corresponding transients would resemble SN Iax events similar to SN 2002cx .
If helium stars in this mass range indeed explode as SNe Ia , then the frequency of events would be comparable to the observed SN Ib/c rates , thereby sufficing to account for the majority of SNe Ia in star-forming galaxies .