Binaries¶
At the moment, NBODY6 and NBODY6++GPU are the only supported codes that have a separate treatment for binary stars. In both cases, the main array of stars contain the centre of mass position and velocity of each binary. The masses are then the total mass of the binary star. Separate parameters are used that contain properties of the individual binaries themselves. These include, but are not limited to:
ids
i_d1
andi_d2
kwtypes
kw1
andkw2
eccentricity
ecc
orbital period
pb
semi-major axis
semi
masses
m1
andm2
luminosities
logl1
andlogl2
It is possible to add binary star properties manually using StarCluster.add_bse
, however clustertools
will always assume the binary’s centre of mass positions and velocities, total mass, and primary star ID were added via StarCluster.add_stars
.
Generally speaking, unit and coordinate transformations do not act on these parameters. They are saved in the event an experienced NBODY6 user would like to view these parameters (see StarCluster.add_bse
for the full list of saved parameters). The only functions designed specifically designed for binaries are to_audays
and to_sudays
. These unit conversion function convert orbital period pb
to units days, semi-major axis semi
to units of solar units (su) or astronomical units (au). When these are called, the masses of individual binary stars (m1
and m2
) are converted to solar masses. When to_nbody
is called, all of these values are returned to nbody units.
More support for binary stars is planned for future releases.