Equal-mass Binaries

To construct a $q=1.0$ irrotational binary configuration, you can use the ``setup2i1'' subroutine, which is called by setting the three letter code in sph.init to ``2i1''.

The particle positions and other important parameters are read in from a file called ``pos.sph'', which you will need to create. We have supplied the code to make an executable called ``b2pos'', which will write this file for you. Based on responses to two questions, it can convert binary output files, in the form ``out012.sph'' (or any other 3-digit number) or ``restart.sph'' into the ASCII pos.sph file. For more on file I/O, please see Sec. 5.

Note that the parameter ``N'' used to initialize the run is essentially ignored, since the number of particles is set by the configuration read in from the files.

Additionally, the run will need you to create an input file called ``axes1.sph''. This file, in ASCII format, consists of three numbers representing the amount by which the spherical model is deformed in each of the three principal axes (x: the center of mass separation vector, y: the orbital velocity, z: the angular momentum axis). Typically, all three values should be $\sim 1$, and more often than not, $a_1>a_2>a_3$. This file will be created for you by the testinput executable discussed above.