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).
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!pip install -I "phoebe>=2.2,<2.3"
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%matplotlib inline
As always, let's do imports and initialize a logger and a new bundle. See Building a System for more details.
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import phoebe
from phoebe import u # units
logger = phoebe.logger()
b = phoebe.default_binary(contact_binary=True)
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b.add_dataset('lc', times=phoebe.linspace(0,0.5,101))
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b.run_compute(irrad_method='none', model='no_spot')
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Let's add a spot to the primary component in our binary. Note that if you attempt to attach to the 'contact_envelope' component, an error will be raised. Spots can only be attached to star components.
The 'colat' parameter defines the latitude on the star measured from its North (spin) Pole. The 'long' parameter measures the longitude of the spot - with longitude = 0 being defined as pointing towards the other star at t0. See to spots tutorial for more details.
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b.add_feature('spot', component='primary', feature='spot01', relteff=0.9, radius=20, colat=90, long=-45)
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b.run_compute(irrad_method='none', model='with_spot')
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afig, mplfig = b.plot(show=True, legend=True)
Since the spots are still defined with the coordinate system of the individual star components, this can result in spots that are distorted and even "cropped" at the neck. Furthermore, spots with long=0 could be completely "hidden" by the neck or result in a ring around the neck.
To see this, let's plot our mesh with teff as the facecolor.
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b.remove_dataset(kind='lc')
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b.remove_model(model=['with_spot', 'no_spot'])
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b.add_dataset('mesh', compute_times=b.to_time(0.25), columns='teffs')
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b.run_compute(irrad_method='none')
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afig, mplfig = b.plot(fc='teffs', ec='face', fcmap='plasma', show=True)
Now if we set the long closer to the neck, we'll see it get cropped by the boundary between the two components. If we need a spot that crosses between the two "halves" of the contact, we'd have to add separate spots to each component, with each getting cropped at the boundary.
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b.set_value('long', value=-30)
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b.run_compute(irrad_method='none')
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afig, mplfig = b.plot(fc='teffs', ec='face', fcmap='plasma', show=True)
If we set long to zero, the spot completely disappears (as there is nowhere in the neck that is still on the surface.
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b.set_value('long', value=0.0)
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b.run_compute(irrad_method='none')
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afig, mplfig = b.plot(fc='teffs', ec='face', fcmap='plasma', show=True)
But if we increase the radius large enough, we'll get a ring.
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b.set_value('radius', value=40)
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b.run_compute(irrad_method='none')
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afig, mplfig = b.plot(fc='teffs', ec='face', fcmap='plasma', show=True)