2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/129066Topological invariants play an important rôle in the theory of gravitational lensing by constraining the image number. Furthermore, it is known that, for certain lens models, the image magnifications $μ_i$ obey invariants of the form $\sum_i μ_i=1$. In this paper, we show that this magnification invariant is the holomorphic Lefschetz number of a suitably defined complexified lensing map, and hence a topological invariant. We also provide a heat kernel proof of the holomorphic Lefschetz fixed point formula which is central to this argument, based on Kotake's proof of the more general Atiyah-Bott theorem. Finally, we present a new astronomically motivated lens model for which this invariant holds.14 pages. Version 2: typos correctedMathematical PhysicsAstrophysicstext