References

• Schneider, Ehlers & Falco (1992), Gravitational Lenses, Springer. (Multiplane lensing formalism.)
• Kormann, Schneider & Bartelmann (1994), Isothermal ellipsoidal mass distributions in gravitational lensing, A&A 284. (SIE deflection angles.)
• Tessore & Metcalf (2015), The elliptical power law profile lens, A&A 580, A79. (Exact closed-form EPL deflection and potential via the angular recurrence used here.)
• Blandford & Narayan (1986), Fermat surface, caustics, and the time delay between images, ApJ 310. (Fermat principle formulation of gravitational lensing; image types and time delays.)
• Orban de Xivry & Marshall (2009), An atlas of predicted exotic gravitational lenses, MNRAS 399. (Swallowtail and butterfly caustic metamorphoses in compound lenses; basis for the Butterfly Caustic preset.)
• Lupton, Blanton, Fekete et al. (2004), Preparing Red-Green-Blue Images from CCD Data, PASP 116. (Asinh stretch for astronomical image display.)
• Smith & van der Walt (2015), matplotlib viridis/inferno/plasma colormaps; Mikhailov (2019), Turbo colormap. (Perceptually uniform palettes; implemented here via compact polynomial fits.)
• lenstronomy (Birrer et al.), LensModel/Profiles/epl_numba.py. (Reference implementation the EPL deflection and potential were ported from and validated against.)