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equation check
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sofiacovarrubias committed Feb 14, 2024
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Expand Up @@ -15,8 +15,9 @@ which can then be solved using Kepler’s equation, but first it is important to
.. Note::
For an interactive visualization to define and help users understand our coordinate system,
you can check out `this GitHub tutorial <https://github.com/sblunt/orbitize/blob/main/docs/tutorials/show-me-the-orbit.ipynb>`_.

There is also a `YouTube video <https://www.youtube.com/watch?v=0e24VUhQmbM>`_
with use and explaination of the coordinate system.
with use and explanation of the coordinate system.

In its “standard” mode, ``orbitize!`` assumes that the user only has relative astrometric data to fit.
In the ``orbitize!`` coordinate system, relative R.A. and declination can be expressed as the following functions
Expand All @@ -29,7 +30,8 @@ of orbital parameters
where 𝑎, 𝑒, :math:`\omega_p`, Ω, and 𝑖 are orbital parameters, and 𝜋 is the system parallax. f is
the true anomaly, and E is the eccentric anomaly, which are related to elapsed time
through Kepler’s equation and Kepler’s third law:
through Kepler’s equation and Kepler’s third law

.. math::
M = 2\pi ({t\over P}-(\tau -\tau_ref))
Expand Down Expand Up @@ -57,7 +59,7 @@ In practice, the reverse logic is often employed: an independent constraint
on the mass of the primary (from e.g., spectroscopic analysis) is used as a prior on
the total mass when the planet mass is small and can be ignored.

A second important degeneracy is between semimajor axis 𝑎, total mass :math:`𝑀_tot`, and
A second important degeneracy is between semimajor axis 𝑎, total mass :math:`𝑀_{tot}`, and
parallax 𝜋. If we just had relative astrometric measurements and no external knowledge of the system parallax,
we would not be able to distinguish between a system
that has larger distance and larger semimajor axis (and therefore larger total mass,
Expand All @@ -73,7 +75,8 @@ and the position angle of nodes Ω. The above defined R.A. and decl. functions a

.. math::
\omega_p' = \omega_p + \pi
\omega' = \omega - \pi
\Omega' = \Omega - \pi
which creates a 180◦ degeneracy between particular values of :math:`\omega_p` and Ω, and
a characteristic “double-peaked” structure in marginalized 1D posteriors of these
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