Heidelberg Institute for Theoretical Studies | 2016 Feb 04
HITS astrophysicists use new methods to simulate the common-envelope phase of binary stars, discovering dynamic irregularities that may help to explain how supernovae evolve.Click to play embedded YouTube video.
When we look at the night sky, we see stars as tiny points of light eking out a solitary existence at immense distances from Earth. But appearances are deceptive. More than half the stars we know of have a companion, a second nearby star that can have a major impact on their primary companions. The interplay within these so-called binary star systems is particularly intensive when the two stars involved are going through a phase in which they are surrounded by a common envelope consisting of hydrogen and helium. Compared to the overall time taken by stars to evolve, this phase is extremely short, so astronomers have great difficulty observing and hence understanding it. This is where theoretical models with highly compute-intensive simulations come in. Research into this phenomenon is relevant understanding a number of stellar events such as supernovae.
Using new methods, astrophysicists Sebastian Ohlmann, Friedrich Röpke, Rüdiger Pakmor, and Volker Springel of the Heidelberg Institute for Theoretical Studies (HITS) have now made a step forward in modeling this phenomenon. As they report in The Astrophysical Journal Letters, the scientists have successfully used simulations to discover dynamic irregularities that occur during the common-envelope phase and are crucial for the subsequent existence of binary star systems. These so-called instabilities change the flow of matter inside the envelope, thus influencing the stars’ distance from one another and determining, for example, whether a supernova will ensue and, if so, what kind it will be. The article is the fruit of collaboration between two HITS research groups, the Physics of Stellar Objects (PSO) group and the Theoretical Astrophysics group (TAP). Prof. Volker Springel’s AREPO code for hydrodynamic simulations was used and adapted for the modeling. It solves the equations on a moving mesh that follows the mass flow, and thus enhances the accuracy of the model. ...
Hydrodynamic moving-mesh simulations of the common envelope phase in binary stellar systems - Sebastian T. Ohlmann et al
- Astrophysical Journal Letters 816(1):L9 (2016 Jan 01) DOI: 10.3847/2041-8205/816/1/L9
arXiv.org > astro-ph > arXiv:1512.04529 > 14 Dec 2015