BSE class hierarchy

The BSE class diagram is shown in Figure 3.

Figure 3 BSE class & container diagram.

The BSE inheritance hierarchy is as follows:

BinaryStar

BaseBinaryStar

Star → BinaryConstituentStar (star1)
Star → BinaryConstituentStar (star2)

The main class for binary star evolution is the BinaryStar class. The BinaryStar class is a wrapper that abstracts away the details of the binary star and the evolution. Internally the BinaryStar class maintains a pointer to an object representing the binary star being evolved, with that object being an instance of the BaseBinaryStar class. The BinaryStar class maintains a pointer to a second object, representing the saved state of the binary star being evolved, with that object also being an instance of the BaseBinaryStar class. The second object is a copy of the binary star being evolved at some earlier timestep, facilitating reverting the binary star to a previous state.

The BaseBinaryStar class is a container class for the objects that represent the component stars of a binary system. An instance of the BaseBinaryStar class is a binary system being evolved by COMPAS, and contains a BinaryConstituentStar class object for each of the component stars (i.e. the primary and secondary stars), as well as data structures and algorithms specific to the evolution of a binary system. The BaseBinaryStar class also maintains pointers to the BinaryConstituentStar class objects considered to be the current donor and accretor during a mass transfer event, as well as pointers to the BinaryConstituentStar class objects considered to be the current supernova and companion star, should one of the stars undergo a supernova event.

The BinaryConstituentStar class inherits from the Star class, so objects instantiated from the BinaryConstituentStar class inherit the characteristics of the Star class, particularly the stellar evolution model. The BinaryConstituentStar class defines member variables and functions that pertain specifically to a constituent star of a binary system but that do not (generally) pertain to single stars that are not part of a binary system (there are some functions that are defined in the BaseStar class and its derived classes that deal with binary star attributes and behaviour – in some cases the stellar attributes that are required to make these calculations reside in the BaseStar class so it is easier and cleaner to define the functions there).

An instance of the BinaryConstituentStar class is a single component star of a binary system being evolved by COMPAS, and inhertis from the Star, so will evolve over time through various SSE classes shown in Figure 1 SSE class & container diagram.. The BinaryConstituentStar class defines additional data structures and algorithms (to the data structures and algorithms provided by the SSE classes) required to support the evolution of a binary system component star.

The BaseBinaryStar class is the main class for the underlying binary star object held by the BinaryStar class. The BaseBinaryStar class defines all member variables that pertain specifically to a binary star, and many member functions that provide binary-star specific functionality. Internally, the BaseBinaryStar class maintains pointers to the two BinaryConstituentStar class objects that constitute the binary star.