Extinction (ebv, Av, & Rv)

Setup

Let's first make sure we have the latest version of PHOEBE 2.2 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>=2.2,<2.3"

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 [2]:
import phoebe
from phoebe import u # units
import numpy as np
import matplotlib.pyplot as plt

logger = phoebe.logger()

b = phoebe.default_binary()

Now let's add a light curve so that we can access the relevant parameters.


In [3]:
b.add_dataset('lc')


Out[3]:
<ParameterSet: 43 parameters | contexts: constraint, dataset, compute, figure>

Relevant Parameters

Extinction is parameterized by 3 parameters: ebv (E(B-V)), Av, and Rv. Of these three, two can be provided and the other must be constrained. By default, ebv is the constrained parameter. To change this, see the tutorial on constraints and the b.flip_constraint API docs.


In [8]:
print(b['ebv'])


ParameterSet: 2 parameters
*               ebv@lc01@dataset: 0.0
                  ebv@constraint: {Av@lc01@dataset} / {Rv@lc01@dataset}

In [10]:
print(b['ebv@dataset'])


Parameter: ebv@lc01@dataset
                       Qualifier: ebv
                     Description: Passband extinction E(B-V)
                           Value: 0.0
                  Constrained by: Av@lc01@dataset, Rv@lc01@dataset
                      Constrains: None
                      Related to: Av@lc01@dataset, Rv@lc01@dataset


In [11]:
print(b['ebv@constraint'])


Constrains (qualifier): ebv
Expression in solar units (value): {Av@lc01@dataset} / {Rv@lc01@dataset}
Current Result (result): 0.0

In [6]:
print(b['Av'])


Parameter: Av@lc01@dataset
                       Qualifier: Av
                     Description: Passband extinction Av
                           Value: 0.0
                  Constrained by: 
                      Constrains: ebv@lc01@dataset
                      Related to: Rv@lc01@dataset, ebv@lc01@dataset


In [7]:
print(b['Rv'])


Parameter: Rv@lc01@dataset
                       Qualifier: Rv
                     Description: Extinction law parameter
                           Value: 3.1
                  Constrained by: 
                      Constrains: ebv@lc01@dataset
                      Related to: Av@lc01@dataset, ebv@lc01@dataset

For more details on the contribution of extinction to observables, see the following example scripts:


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