Orbital geometry (lazuli_exo.orbit)

Orbital geometry helpers shared by the precompute scripts and the runtime.

lazuli_exo.orbit.transit_duration_s(period_d, a_over_rs, rp_rs, inc_deg=90.0, ecc=0.0, w_deg=90.0)

Total transit duration T14 in seconds (Winn 2010, eqs. 14 and 16).

Impact parameter and duration both carry the eccentric conjunction- distance / velocity factors. Returns 0.0 for a non-transiting geometry.

lazuli_exo.orbit.projected_separation(t_s, period_d, a_over_rs, inc_deg=90.0, ecc=0.0, w_deg=90.0)

Sky-projected star-planet separation z(t) in stellar radii for a Keplerian orbit (Winn 2010, eqs. 2-5), t_s seconds from mid-transit.

Mid-transit is inferior conjunction (true anomaly f = pi/2 - w, planet in front of the star, batman/jaxoplanet convention), so z(0) is the eccentric impact parameter. Kepler’s equation is solved by vectorised Newton iteration; for ecc = 0 this reduces to the circular arc.