Accretion-induced collapse ( AIC ) occurs when an O/Ne white dwarf ( WD ) grows to nearly the Chandrasekhar mass ( M _ { Ch } ) , reaching central densities that trigger electron captures in the core .
Using Modules for Experiments in Stellar Astrophysics ( MESA ) , we present the first true binary simulations of He star + O/Ne WD binaries , focusing on a 1.5 M _ { \odot } He star in a 3 hour orbital period with 1.1 - 1.3 M _ { \odot } O/Ne WDs .
The helium star fills its Roche lobe after core helium burning is completed and donates helium on its thermal timescale to the WD , \dot { M } \approx 3 \times 10 ^ { -6 } M _ { \odot } /yr , a rate high enough that the accreting helium burns stably on the WD .
The accumulated carbon/oxygen ashes from the helium burning undergo an unstable shell flash that initiates an inwardly moving carbon burning flame .
This flame is only quenched when it runs out of carbon at the surface of the original O/Ne core .
Subsequent accumulation of fresh carbon/oxygen layers also undergo thermal instabilities , but no mass loss is triggered , allowing M _ { WD } \rightarrow M _ { Ch } , triggering the onset of AIC .
We also discuss the scenario of accreting C/O WDs that experience shell carbon ignitions to become O/Ne WDs , and then , under continuing mass transfer , lead to AIC .
Studies of the AIC event rate using binary population synthesis should include all of these channels , especially this latter channel , which has been previously neglected but might dominate the rate .