meepmeep.numba3d.zvel_c

meepmeep.numba3d.zvel_c(time: float | ndarray[tuple[Any, ...], dtype[_ScalarT]], c: ndarray[tuple[Any, ...], dtype[_ScalarT]]) → float | ndarray[tuple[Any, ...], dtype[_ScalarT]]

Evaluate the planet’s line-of-sight velocity component at an expansion-point-centered time.

Centered counterpart of zvel. Only the z-direction coefficients (row 2 of c) are read, making this the cheapest velocity evaluator in the module. The polynomial is the analytic derivative of the position z-polynomial, 4th-order in time.

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

Time relative to the Taylor series expansion point.

cNDArray

A (3, 5) coefficient matrix produced by solve3d. Only row 2 (the z-direction coefficients) is read.

Returns:

vzfloat or NDArray

Line-of-sight z velocity in stellar radii per unit time. Positive values indicate motion toward the observer.

Notes

Useful for radial-velocity computations, where only the line-of-sight component matters; see rv_c / rv.