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.

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.

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.

Mass Transfer case

The mass transfer cases 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.

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)