The single-degenerate (SD) model is one of the leading models for the progenitors of Type Ia supernovae (SNe Ia). Recently, a new version of the SD model, the common-envelope wind (CEW) model, has been proposed. In principle, it has the potential to resolve most of the difficulties encountered by previous SD models.
This model is still being developed, and several open issues remain, such as the details of the mass-loss mechanism from the surface of the common envelope (CE), the main observational properties, and the spiral-in timescale of the binary inside the envelope.
In a new study, scientists from the Chinese Academy of Sciences (CAS) aim to address these issues by considering hydrodynamical effects on the CE. By performing hydrodynamic simulations on the common-envelope wind model of type Ia supernovae (SNe Ia), they revealed the mass loss mechanism and the main observational features of white dwarf binaries in the common-envelope wind phase.
The simulations show that such systems are always dynamically unstable and produce dramatic mass loss, resulting in an envelope mass of only a few thousand solar mass.
They discovered by examining the internal structure that the same mechanism that causes the pulsating excitation of traditional Cepheids was responsible for this instability—ionization-recombination processes of hydrogen and helium in the envelope.
The Hertzsprung-Russell diagram showed that the common-envelope wind model’s evolutionary trajectory’s center was situated within the classical Cepheid instability strip, suggesting that this system might be observed as periodic variable stars.
This result can provide theoretical guidance for the subsequent observational search for the progenitor system of SNe Ia.