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import phoebe
import numpy as np
import matplotlib.pyplot as plt
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b = phoebe.default_binary()
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b.add_dataset('lc')
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b.add_compute('ellc')
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And to avoid any issues with falling outside the atmosphere grids, we'll set a simple flat limb-darkening model and disable irradiation.
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b.set_value_all('ld_mode', 'manual')
b.set_value_all('ld_func', 'linear')
b.set_value_all('ld_coeffs', [0.5])
b.set_value_all('irrad_method', 'none')
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b.set_value_all('atm', 'ck2004')
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requiv_max = b.get_value('requiv_max', component='primary', context='component')
requiv_max_factors = np.arange(0.3,1.0,0.05)
sb_pblum_abs = np.zeros_like(requiv_max_factors)
ph_pblum_abs = np.zeros_like(requiv_max_factors)
for i,requiv_max_factor in enumerate(requiv_max_factors):
b.set_value('requiv', component='primary', value=requiv_max_factor*requiv_max)
sb_pblum_abs[i] = b.compute_pblums(compute='ellc01', pblum_method='stefan-boltzmann', pblum_abs=True)['pblum_abs@primary@lc01'].value
ph_pblum_abs[i] = b.compute_pblums(compute='ellc01', pblum_method='phoebe', pblum_abs=True)['pblum_abs@primary@lc01'].value
Here we can see that Stefan-Boltzmann (which assumes spherical stars) is an increasingly bad approximation as the distortion of the star increase (as expected). But even in the quite detached case, the luminosities are not in great agreement. For this reason it is important to not trust absolute pblum values when using pblum_method='stefan-boltzmann', but rather just use them as a nuisance parameter or original estimate to adjust the light-levels.
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_ = plt.plot(requiv_max_factors, sb_pblum_abs, 'k-', label='Stefan-Boltzmann')
_ = plt.plot(requiv_max_factors, ph_pblum_abs, 'b-', label='PHOEBE mesh')
_ = plt.xlabel('requiv / requiv_max')
_ = plt.ylabel('L (W)')
_ = plt.legend()
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