The BinaryStar object

The BinaryStar object is composed of two SingleStar objects and contains the current and past states of the binary. Only parameters in the BINARYPROPERTIES list are stored in the history. The current parameter value of the star object is accessed as, e.g. binary.orbital_period while his past history with binary.orbital_period_history. The two stars are accesses as, e.g. binary.star_1.mass while his past history with binary.star_1.mass_history.

To use BinaryStar object import it using:

from posydon.binary_evol.singlestar import SingleStar
from posydon.binary_evol.binarystar import BinaryStar

Creating a BinaryStar object

BINARYPROPERTIES

The binary properties are defined as follows

BINARYPROPERTIES

Properties	Descriptions
state	The state of the binary, see state options.
event	The event of the binary, see event options.
time	Age of the binary system in yr.
separation	Orbital separation in R_sun.
orbital_period	Orbital period in days.
eccentricity	Orbital eccentricity.
V_sys	Velocity of the centre of mass of the binary [Vx, Vy, Vz] in km/s.
mass_transfer_case	Mass transfer case, see MT case options.
lg_mtransfer_rate	the logarithm of the mass transfer rate in Msun/yr.
step_names	Names of the steps in the evolution.
step_times	‘Time spend in the steps in the evolution.’
rl_relative_overflow_1	The relative overflow of the Roche Lobe of star 1.
rl_relative_overflow_2	The relative overflow of the Roche Lobe of star 2.
trap_radius	The trapping radius of the binary in R_sun.
acc_radius	The accretion radius of the binary in R_sun.
t_sync_rad_1	?
t_sync_conv_1	?
t_sync_rad_2	?
t_sync_conv_2	?
nearest_neighbour_distance	The distance to the nearest neighbour for NN interpolation.

Additional scalar properties can be added during the evolution.

Since they do not change over time, they are not stored in the history. These can requested and will be stored in the output oneline (See the Synthetic Populatiohn and Population Parameter Guide for more information).

State options

Binary states are defined according to the following table:

States

State	Description
detached	The stars in the binary are in a detached state.
contact	The stars in the binary are in contact.
RLO1	The binary is Roche Lobe overflowing, star 1 is overfilling the RL.
RLO2	The binary is Roche Lobe overflowing, star 2 is overfilling the RL.
CE	The binary is in a Common Envelope phase.
disrupted	The binary was disrupted.
MaxTimeChanged	Max time of the evolution was reached.

TODO: update properties

Event options

Binary events are defined according to the following table:

Events

State	Description
CC1	Core collapse of star 1.
CC2	Core collapse of star 2.
oRLO1	The binary is at onset of Roche Lobe overflow, star 1 is overfilling the RL.
oRLO2	The binary is at onset of Roche Lobe overflow, star 2 is overfilling the RL.
oCE	The binary is at the onset of Common Envelope.
None	No event occurred.
END	The binary evolution was stopped.

TODO: update properties

Mass Transfer case

The mass transfer cases are stored in mt_history_GRIDTYPE and are defined according to the following table: TODO: add the table below

Mass transfer cases

State	Description
None	The binary is not Roche Lobe overflowing.

TODO: update properties

Basic example

The simplest method is to provide the two star objects and kwargs of the initial binary parameters.

kwargs1 = {'state' : 'MS',
           'mass' : 20.0,
           'metallicity' : 0.014}

star_1 = SingleStar(**kwargs1)

kwargs2 = {'state' : 'MS',
           'mass' : 10.0,
           'metallicity' : 0.014}

star_2 = SingleStar(**kwargs2)

kwargs3 = {'state' : 'detached',
           'event' : None,
           'time' : 0.,
           'orbital_period' : 3.,
           'eccentricity' : 0.}


binary = BinaryStar(star_1, star_2, **kwargs3)