meepmeep.numba3d.cos_alpha

meepmeep.numba3d.cos_alpha(time: float | ndarray[tuple[Any, ...], dtype[_ScalarT]], tc: float, p: float, c: ndarray[tuple[Any, ...], dtype[_ScalarT]], te: float = 0.0) → float | ndarray[tuple[Any, ...], dtype[_ScalarT]]

Evaluate the cosine of the orbital phase angle at an absolute time.

Folds the absolute observation time back to an expansion-point-centered offset and delegates to the centered kernel. The phase angle alpha is the star-planet-observer angle. With z positive toward the observer, cos alpha = -z / r where r = sqrt(x^2 + y^2 + z^2). At superior conjunction (full phase, planet behind star) cos alpha = +1; at inferior conjunction (new phase, planet in front) cos alpha = -1.

Accepts a scalar time or a 1-D array of times and dispatches to the appropriate kernel at compile time (inside @njit) or at call time (pure Python).

Parameters:

timefloat or NDArray

Absolute observation time(s).

tcfloat

Transit-centre time (time of inferior conjunction), on the same time axis as time.

pfloat

Orbital period.

cNDArray

A (3, 5) coefficient matrix produced by solve3d.

tefloat, optional

Expansion-point offset from the transit centre [days] - the same value that was passed to solve3d. Defaults to 0.0, the expansion point at the transit centre.

Returns:

cos_alphafloat or NDArray

Cosine of the phase angle, in [-1, 1].