API/Reference

SimpleOrbit(; period, duration, t0=0, b=0.0)

Circular orbit parameterized by the basic observables of a transiting system.

Parameters

• period - The orbital period of the planets, nominally in days
• duration - The duration of the transit, similar units as period.
• t0 - The midpoint time of the reference transit, similar units as period
• b - The impact parameter of the orbit, unitless

KeplerianOrbit(; kwargs...)

Keplerian orbit parameterized by the basic observables of a transiting 2-body system.

The following units are used by default: * d: Days * R⊙: Solar radius * M⊙: Solar mass * M⊙/R⊙³: Solar density * rad: Radians

Parameters

• period/P – The orbital period of the planet [d].
• t0/t_0 – The midpoint time of the reference transit [d].
• tp/t_p – The time of periastron [d].
• duration/τ/T – The transit duration [d].
• a – The semi-major axis [R⊙].
• aR_star/aRs – The ratio of the semi-major axis to star radius.
• R_planet/Rp – The radius of the planet [R⊙].
• R_star/Rs – The radius of the star [R⊙].
• rho_star/ρ_star – The spherical star density [M⊙/R⊙³].
• r/RpRs – The ratio of the planet radius to star radius.
• b – The impact parameter, bounded between 0 ≤ b ≤ 1.
• ecc/e – The eccentricity of the closed orbit, bounded between 0 ≤ ecc < 1.
• incl – The inclination of the orbital plane relative to the axis perpendicular to the reference plane [rad]
• omega/ω – The argument of periapsis [rad].
• cos_omega/cos_ω – The cosine of the argument of periapsis.
• sin_omega/sin_ω – The sine of the argument of periapsis.
• Omega/Ω – The longitude of the ascending node [rad].
• M_planet/Mp – The mass of the planet [M⊙].
• M_star/Ms – The mass of the star [M⊙].

Valid combinations

The following flowchart can be used to determine which parameters can define a KeplerianOrbit:

1. The period or a must be given. If both given, then neither M_star or rho_star can be defined because the stellar density is now implied.
2. Only incl or b can be given.
3. If ecc is given, then omega must also be given.
4. If no stellar parameters are given, the central body is assumed to be the Sun. If only rho_star is given, then R_star is defined to be 1 solar radius. Otherwise, at most two of M_star, R_star, and rho_star can be given.
5. Either t0 or tp must be given, but not both.

relative_position(::AbstractOrbit, t)

The relative position, [x, y, z], of the companion compared to the host at time t. In other words, this is the vector pointing from the host to the companion along the line of sight. Nominally, the units of this distance are relative to the host's radius. For example, a distance of 2 is 2 stellar radii.

separation(::AbstractOrbit, t)

Calculates the separation of the companion at time t

position_angle(::AbstractOrbit, t)

Calculates the position angle (in degrees) of the companion at time t

flip(::AbstractOrbit)

Return a new orbit with the primary and secondary swapped.