*Introduction to Binary Neutron Star Systems*

##
**Equilibrium Polytrope**

The above images exhibit the stars used in the calculation when they are isolated and in spherical equilibrium. The stars are modeled in full general relativity as polytropes with a polytropic index n=1. For this calculation, the stars were created with a radius R = 11.4 M, where M is the total mass-energy, and with a rest mass M_{0} that is 55% of the maximum allowed rest mass of an isolated, nonrotating star.

##
** Density Profile of Isolated Polytrope**

Here we display the density profile of the isolated neutron star as seen in the equatorial plane. Numbers are in nondimensional units.

##
**Corotating Binary Neutron Star System**

Two identical polytropes of the type described above are now placed in a corotating circular binary orbit. They are separated by a coordinate distance r = 27.4 M_{0} initially, where M_{0} is the mass of an individual neutron star.

##
**Definition of Z**_{A} parameter

We use the quantity Z_{A}, as defined in the above image, to parametrize the binary separation. This parameter is defined so that infinitely separated binaries correspond to Z_{A} = 1, while grazing binaries correspond to Z_{A} = 0.

*last updated 23 apr 01 jjm *