meepmeep.numba3d.cos_alpha_o

meepmeep.numba3d.cos_alpha_o(t, tpa, p, dt, ep_table, ep_times, coeffs)

Cosine of the phase angle for any orbital phase.

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

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) \(\cos\alpha = -1\).

Parameters:

tfloat or ndarray

Time(s) at which to evaluate the phase angle.

tpa, p, dt, ep_table, ep_times, coeffs

See pos_o().

Returns:

cos_alphafloat or ndarray

Cosine of the phase angle, in \([-1, 1]\). Arrays of shape (N,) for an array t.