energy.sph, biout.sph, gwdata.sph, com.sph, and spin.sph

The code also writes to a number of ASCII output files every timestep.

The file energy.sph lists the current time, and then the total system potential energy, kinetic energy, internal energy, total energy, total entropy, total angular momentum, and the maximum SPH density for any particle. These quantities are defined by the sums:

$$P.E. = 0.5\sum_i m_i \Phi_i,$$ (40)

$$K.E. = 0.5 \sum_i m_i v_i^2,$$ (41)

$$I.E. = \frac{1}{\Gamma-1}\sum_i A_i \rho_i^{\Gamma-1},$$ (42)

$$E_T = P.E.+K.E.+I.E.,$$ (43)

$$S_T = \frac{1}{\Gamma-1}\sum_i m_i \ln\left(\frac{A_i}{\Gamma-1}\right).$$ (44)

The file biout.sph lists the current time, the binary separation, the angle between the x-axis and the line connecting the stars' centers-of-mass, the distances for each star between the star's center-of-mass and the furthest particle from it, and the angles for each star between the center-of-mass and the furthest particle.

The file gwdata.sph contains the current time, and then the second time derivatives of the quadrupole moments. Note that we do not subtract out the trace of the quadrupole tensor beforehand. To calculate the gravitational waveform, take the appropriate linear combination of these terms. See Faber & Rasio (2000) for the way we have done this. We have generally found the first and last value for the quadrupole moments to be a bit inaccurate, especially if you wish to finite difference to find the gravitational wave luminosity, Feel free to discard the first and last lines of each file.

The file com.sph stores the current time, and then the position and velocity of the centers-of-mass of each star.

The file spin.sph stores the current time, and then the angular momentum of each star around its own center of mass. Note that we give the angular momentum in 5 directions, x, y, and z, as well as two directions rotated 45 degrees from the x and y directions in the x-y plane. These are appropriate to the case of hyperbolic binaries, for which the self-spin vectors lie primarily in the ``plus'' direction due to the way we construct the initial orbit. See Sec. 4.5 for more info about this.

All of these files can be safely commented out or edited to meet your needs. Note that they are opened upon the start of the code, and not closed until it terminates. Thus, data is only written to them every time the buffer size exceeds a system-dependent value, and a run which is stopped midway through will not contain all of the calculated values.