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71 changes: 43 additions & 28 deletions posydon/binary_evol/CE/step_CEE.py
Original file line number Diff line number Diff line change
Expand Up @@ -77,49 +77,64 @@
"record_matching": False
}


# common_envelope_option_for_lambda:
# 1) 'default_lambda': using for lambda the constant value of
# common_envelope_lambda_default parameter
# 2) 'lambda_from_grid_final_values': using lambda parameter from MESA history
# which was calulated ni the same way as method (5) below
# 3) 'lambda_from_profile_gravitational': calculating the lambda parameter
# from the donor's profile by using the gravitational binding energy from the
# surface to the core (needing "mass", and "radius" as columns in the profile)
# 4) 'lambda_from_profile_gravitational_plus_internal': as above but taking
# into account a factor of common_envelope_alpha_thermal * internal energy too
# in the binding energy (needing also "energy" as column in the profile)
# 5) 'lambda_from_profile_gravitational_plus_internal_minus_recombination':
# as above but not taking into account the recombination energy in the internal
# energy (needing also "y_mass_fraction_He", "x_mass_fraction_H",
# "neutral_fraction_H", "neutral_fraction_He", and "avg_charge_He" as column
# in the profile)
# the mass fraction of an element which is used as threshold to define a core,

class StepCEE(object):
"""Compute supernova final remnant mass, fallback fraction & stellar state.

This consider the nearest neighboor of the He core mass of the star,
previous to the collapse. Considering a set of data for which the He core
mass of the compact object projenitos previous the collapse, the final
remnant mass and final stellar state of the compact object is known.
"""Handle common envelope evolution (CEE) for binary systems.

This class computes the outcome of a common envelope phase for binary
systems containing a giant star. It calculates how much the orbit must
shrink in order to expel the envelope using the alpha-prescription.
If at the required post-CEE separation one of the stars fills its Roche lobe,
the system is considered a merger. Otherwise, the envelope is lost,
leaving a binary system with the core of the donor star (which initiates
the unstable CEE) and the core of the companion.

If stellar profiles are available, the lambda parameter for the donor
can be calculated directly from the profile. Otherwise, default values
are used. The evolution is computed using a specified prescription
(e.g., alpha-lambda) which determines the final state of the binary
based on energy budget considerations.

Parameters
----------
verbose : bool
If True, the messages will be prited in the console.
If True, the messages will be printed in the console.

Keyword Arguments
-----------------
prescription : str
Prescription to use for computing the prediction of common enevelope
Prescription to use for computing the prediction of common envelope
evolution. Available options are:

* 'alpha-lambda' : Considers the the alpha-lambda prescription
* 'alpha-lambda' : Considers the alpha-lambda prescription
described in [1]_ and [2]_ to predict the outcome of the common
envelope evolution. If the profile of the donor star is available
then it is used to compute the value of lambda.

common_envelope_option_for_lambda : str
Method for calculating the lambda parameter. Available options are:

* 'default_lambda' : Use a constant value from the
`common_envelope_lambda_default` parameter.

* 'lambda_from_grid_final_values' : Use the lambda parameter from
MESA history, calculated using the same method as option 5 below.
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I suggest we make this a numbered list so that the reference to "option 5" is more clear.


* 'lambda_from_profile_gravitational' : Calculate lambda from the
donor's profile using the gravitational binding energy from the
surface to the core (requires "mass" and "radius" columns in the
profile).

* 'lambda_from_profile_gravitational_plus_internal' : As above,
but also accounting for a factor of `common_envelope_alpha_thermal`
times the internal energy in the binding energy (requires also
"energy" column in the profile).

* 'lambda_from_profile_gravitational_plus_internal_minus_recombination' :
As above, but excluding the recombination energy from the internal
energy calculation (requires also "y_mass_fraction_He",
"x_mass_fraction_H", "neutral_fraction_H", "neutral_fraction_He",
and "avg_charge_He" columns in the profile).

References
----------
.. [1] Webbink, R. F. (1984). Double white dwarfs as progenitors of R
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