Critical Radii: Detached Systems

Setup

Let's first make sure we have the latest version of PHOEBE 2.1 installed. (You can comment out this line if you don't use pip for your installation or don't want to update to the latest release).



In [ ]:

    
!pip install -I "phoebe>=2.1,<2.2"

As always, let's do imports and initialize a logger and a new Bundle. See Building a System for more details.



In [1]:

    
%matplotlib inline



In [1]:

    
import phoebe
from phoebe import u # units
import numpy as np
import matplotlib.pyplot as plt

logger = phoebe.logger()

b = phoebe.default_binary()

Detached Systems

Detached systems are the default case for default_binary. The requiv_max parameter is constrained to show the maximum value for requiv before the system will begin overflowing at periastron.



In [2]:

    
b['requiv_max@component@primary']









    Out[2]:





<Parameter: requiv_max=2.01327517654 solRad | keys: description, value, quantity, default_unit, limits, visible_if, copy_for>



In [3]:

    
b['requiv_max@constraint@primary']









    Out[3]:





<ConstraintParameter: {requiv_max@primary@component} = requiv_L1({q@binary@component}, {syncpar@primary@component}, {ecc@binary@component}, {sma@binary@component}, {incl@primary@component}, {long_an@primary@component}, {incl@binary@component}, {long_an@binary@component}, 1) (solar units) => 2.01327517654 solRad>

We can see that the default system is well within this critical value by printing all radii and critical radii.



In [5]:

    
print(b.filter(qualifier='requiv*', context='component'))









    



ParameterSet: 4 parameters
        requiv@primary@component: 1.0 solRad
*   requiv_max@primary@component: 2.01327517654 solRad
      requiv@secondary@component: 1.0 solRad
* requiv_max@secondary@component: 2.01327517654 solRad

If we increase 'requiv' past the critical point, we'll receive a warning from the logger and would get an error if attempting to call b.run_compute().



In [6]:

    
b['requiv@primary'] = 2.2









    



Fri, 01 Feb 2019 11:15 PARAMETERS   WARNING primary is overflowing at periastron (requiv=2.2, requiv_max=2.01327517654)  If not addressed, this warning will continue to be raised and will throw an error at run_compute.



In [7]:

    
print(b.run_checks())









    



(False, 'primary is overflowing at periastron (requiv=2.2, requiv_max=2.01327517654)')

If the value of requiv was exactly the critical value, we'd have a semi-detached system. Alternatively, we could use a constraint to enforce that a system remains semi-detached.

If the value of requiv is over the critical value, the system is overflowing and will raise an error. If we intentionally want a contact system, we can explicitly create a contact system.