https://github.com/simonrw/ttvfast-python

Python interface to the TTVFast library
https://github.com/simonrw/ttvfast-python

Last synced: over 1 year ago
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Python interface to the TTVFast library

• Host: GitHub
• URL: https://github.com/simonrw/ttvfast-python
• Owner: simonrw
• License: gpl-2.0
• Created: 2015-02-22T21:24:56.000Z (over 11 years ago)
• Default Branch: master
• Last Pushed: 2020-06-11T08:15:47.000Z (about 6 years ago)
• Last Synced: 2024-05-22T04:32:05.004Z (about 2 years ago)
• Language: Python
• Size: 230 KB
• Stars: 14
• Watchers: 5
• Forks: 6
• Open Issues: 5
• Metadata Files:
  • Readme: README.rst
  • Changelog: CHANGELOG.rst
  • License: LICENSE

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README

          
=======

TTVFast

=======

:Author: Simon Walker 

.. image:: https://img.shields.io/pypi/v/ttvfast.svg?maxAge=2592000

    :target: https://pypi.python.org/pypi/ttvfast

.. image:: https://travis-ci.org/mindriot101/ttvfast-python.svg?branch=master

    :target: https://travis-ci.org/mindriot101/ttvfast-python

A Python wrapper around Katherine Deck's TTVFast C program (https://github.com/kdeck/TTVFast)

For the latest changes, see `the CHANGELOG `_.

Installation

============

For contributing to the package, see the `Development instructions`_.

Install from pypi:

    ``pip install ttvfast``

For the latest development version, install with pip:

    ``pip install git+https://github.com/mindriot101/ttvfast.git``

Development instructions

------------------------

To contribute to ``ttvfast``, clone the repository and fetch the submodule::

    git clone https://github.com/mindriot101/ttvfast-python.git

    cd ttvfast-python

    git submodule init

    git submodule update # grabs code from TTVFast

install the package, in "development mode" into the current python environment::

    pip install -e .

This way any python code changes made to the current directory will be reflected in the package. Note: any changes to the C code require recompilation by reinstalling the package with ``pip install -e .`` (see the `editable install documentation `_ documentation for more information).

Once the package is installed, test that everything built properly using::

    $ py.test 

    ============================== test session starts ===============================

    testing/test_lweiss.py .

    testing/test_models.py ...

    testing/test_python_api.py ...

    testing/test_ttvfast.py ...

Usage

=====

To compute the TTV properties for one or more planets: 

- build a ``ttvfast.models.Planet`` instance (see the class documentation for required parameters)

- pass a list of the planets in the system to ``ttvfast.ttvfast`` along with:

  - the stellar mass in units of solar mass,

  - the start point of the integration in days,

  - the time step for the integration in days,

  - and the end point for integration in days.

The function ``ttvfast.ttvfast`` returns a dictionary containing ``positions`` and ``rv``. The ``positions`` entry is a tuple of:

1. a list of integer indices for which values correspond to which planet,

2. a list of integers defining the epoch,

3. a list of times,

4. a list of rsky values, and

5. a list of vsky values.

The optional ``rv_times`` parameter takes a list of RV times on which the RV is to be calculated. If so the ``rv`` entry in the output 

dictionary is populated with a list of RV values, and otherwise ``None``.

For example:

.. code-block:: python

    from ttvfast import models

    gravity = 0.000295994511                        # AU^3/day^2/M_sun

    stellar_mass = 0.95573417954                    # M_sun

    planet1 = models.Planet(

        mass=0.00002878248,                         # M_sun

        period=1.0917340278625494e+01,              # days

        eccentricity=5.6159310042858110e-02,

        inclination=9.0921164935951211e+01,         # degrees

        longnode=-1.1729336712101943e-18,           # degrees

        argument=1.8094838714599581e+02,            # degrees

        mean_anomaly=-8.7093652691581923e+01,       # degrees

    )

    planet2 = models.Planet(

        mass=0.00061895914,

        period=2.2266898036209028e+01,

        eccentricity=5.6691301931178648e-02,

        inclination=8.7598285693573246e+01,

        longnode=4.6220554014026838e-01,

        argument=1.6437004273382669e+00,

        mean_anomaly=-1.9584857031843157e+01,

    )

    planets = [planet1, planet2]

    Time = -1045                                    # days

    dt = 0.54                                       # days

    Total = 1700                                    # days

    results = ttvfast.ttvfast(planets, stellar_mass, Time, dt, Total)

For more details, see the original C module's documentation: https://github.com/kdeck/TTVFast/blob/master/c_version/README

Citations

=========

If you use this code, please cite Deck, Agol, Holman, & Nesvorny (2014),

ApJ, 787, 132, arXiv:1403.1895.

-Katherine Deck, Eric Agol, Matt Holman, & David Nesvorny