A model of a carbon-oxygen ( C–O ) presupernova core with an initial mass 1.33 M _ { \odot } , an initial carbon mass fraction X ^ { ( 0 ) } _ { C } = 0.27 , and with an average mass growth-rate 5 \cdot 10 ^ { -7 } M _ { \odot } \mbox { yr } ^ { -1 } due to accretion in a binary system was evolved from initial density \rho _ { c } = 10 ^ { 9 } \mbox { g cm } ^ { -3 } , and temperature T _ { c } = 2.05 \cdot 10 ^ { 8 } K through convective core formation and its subsequent expansion to the carbon runaway at the center .
The only thermonuclear reaction contained in the equations of evolution and runaway was the carbon burning reaction ^ { 12 } C + ^ { 12 } C with an energy release corresponding to the full transition of carbon and oxygen ( with the same rate as carbon ) into ^ { 56 } Ni .
As a parameter we take \alpha _ { c } — a ratio of a mixing length to the size of the convective zone .
In spite of the crude assumptions , we obtained a pattern of the runaway acceptable for the supernova theory with the strong dependence of its duration on \alpha _ { c } .
In the variants with large enough values of \alpha _ { c } = 4.0 \cdot 10 ^ { -3 } and 3.0 \cdot 10 ^ { -3 } the fuel combustion occurred from the very beginning as a prompt detonation .
In the range of 2.0 \cdot 10 ^ { -3 } \geq \alpha _ { c } \geq 3.0 \cdot 10 ^ { -4 } the burning started as a deflagration with excitation of stellar pulsations with growing amplitude .
Eventually , the detonation set in , which was activated near the surface layers of the presupernova ( with m \simeq 1.33 M _ { \odot } ) and penetrated into the star down to the deflagration front .
Excitation of model pulsations and formation of a detonation front are described in detail for the variant with \alpha _ { c } = 1.0 \cdot 10 ^ { -3 } .