A New Evolutionary Path for the Progenitors of Type IA Supernovae

Abstract

At present day it is widely accepted that type Ia Supernovae (SNe Ia) are produced by the thermonuclear disruption of CO White Dwarfs (WDs) which accrete mass from their companions in binary systems. In this way the accreting WD can attain the Chandrasekhar mass limit (M _ch) so that C-burning is ignited in highly degenerate physical conditions, thus producing an explosion. The matter accreted onto the WD can be composed mainly by hydrogen (Single Degenerate scenario) or by a mixture of carbon and oxygen (Double Degenerate scenario). The latter scenario is currently considered not promising as SNe Ia progenitor system, mainly for two reasons: 1) the observational search of DD systems composed by two CO WDs with total mass of the order of M _ch and the right initial separation to provide the merging via gravitational wave radiation (GWR) emission in a time smaller than the Hubble time has provided negative results; 2) the extant numerical models of these systems suggest that if a merging occurs, the effective accretion rate onto the more massive WD is very high (∼ 10^-5M⊙yr ^-1 — see [12], [2], [1], [9], [7]) in such a way that off-center C-burning is ignited well before the WD could attain M _ch; in this case the final outcome is an O-Ne-Mg WD, not a SN event ([7], [9], [10]).