Exponential Radius Evolution and Photogravitational Consistency in Near-Eddington Stars

We present a reproducible framework for testing radiative–gravitational balance in luminous stars near the Eddington limit. Using the photogravitational index Φ = L/(Mg), we validate observational consistency and recover the exponential radius evolution timescale. Applications to WR 20a and NGC 3603 A1a confirm the framework as a benchmark for high-luminosity stellar envelopes.