New Insights into Cataclysmic Variables: The Role of a Third Star

Recent research led by astronomers at the California Institute of Technology (Caltech) has revealed that a third star may play a crucial role in the formation of certain cataclysmic variable (CV) systems. This discovery expands the understanding of how these explosive star systems, characterized by white dwarfs stealing mass from their companions, come together. The study, published in the Publications of the Astronomical Society of the Pacific, highlights the implications of these findings for astronomical theories surrounding binary star systems.

The research, which was co-authored by Kareem El-Badry, assistant professor of astronomy at Caltech, and graduate student Cheyanne Shariat, suggests that approximately 10% of known CVs are part of hierarchical triple star systems. Traditionally, the formation of CVs was explained through a mechanism known as common envelope evolution, where two stars are enveloped in a shared gas envelope that drives them closer together. However, the new findings indicate that a third star, orbiting at a distance, may actually be instrumental in bringing the two primary stars together.

"Our results are revealing another formation channel for CVs," El-Badry stated. The study noted that the gravitational influence of a third star can lead to a super-eccentric orbit of the binary pair, facilitating mass transfer from the companion star to the white dwarf.

Utilizing data from the now-retired European Space Agency's Gaia mission, the researchers identified 50 CVs within hierarchical triple systems. They conducted simulations to explore how these triples evolve over time, leading to the formation of CVs without the necessity for the common envelope evolution process. The simulations showed that, in some cases, the third star could significantly alter the dynamics of the binary system, leading to mass transfer events that characterize CVs.

The implication of these findings extends beyond mere academic interest; they challenge long-held beliefs about CV formation and suggest that astrophysical models need to account for the presence of third stars. This new perspective could influence future research on star formation and the dynamics of stellar systems.

In conclusion, this study not only enhances the understanding of cataclysmic variables but also opens avenues for further exploration into the complex interactions within multiple star systems. As astronomers continue to unravel the mysteries of the universe, such groundbreaking insights will play a critical role in shaping contemporary astrophysics.

The research was conducted in collaboration with Smadar Naoz from UCLA, and was supported by funding from various institutions including NASA and the National Science Foundation. The findings prompt a reevaluation of how star systems are theorized to evolve, emphasizing the importance of considering multiple star dynamics in future studies.