The single-degenerate (SD) model is one of the leading models for the progenitors of Type Ia supernovae (SNe Ia). A new version of the SD model has recently been proposed, the common-envelope wind (CEW) model. In principle, it has the potential to solve most of the problems that previous SD models faced.
This model is still in development and there are several outstanding issues, such as the details of the mass loss mechanism of the common envelope (CE) surface, key sensing properties, and the spiral time scale of the binary within the envelope.
In a new study, scientists from the Chinese Academy of Sciences (CAS) are trying to address these issues by accounting for hydrodynamic 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 key observational features of white dwarf binaries in the common-envelope wind phase.
The simulations show that such systems are always dynamically unstable and cause dramatic mass loss, resulting in an envelope mass of only a few thousand solar masses.
They discovered by examining the internal structure that the same mechanism that causes the pulsatile 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 center of the evolutionary trajectory of the common-envelope wind model was within the classical Cepheid instability band, suggesting that this system can be observed as periodically variable stars.
This result may provide theoretical guidance for the subsequent observational search for the SNeIa precursor system.
Magazine reference:
- Yingzhen Cui, Xiangcun Meng, et al. Hydrodynamic simulations for the common envelope wind model for Type Ia supernovae. Astronomy and Astrophysics. DOI: 10.1051/0004-6361/202141335
