Revisiting Wolf-Rayet Masses Through the Photogravitational Parameter Φ

This work develops a new method to measure Wolf–Rayet (WR) star masses using observable surface properties (luminosity, radius, and gravity) through the photogravitational parameter Φ. Calibrated on 12 binaries with secure dynamical masses, the method was applied to 30 apparently single WR stars in the Milky Way and the Large Magellanic Cloud. Our key finding is a systematic deficit: WR stars appear to have 43% less mass than predicted by current evolutionary models, with individual cases ranging from 30–54%. This deficit is consistent across metallicity and subtype, including extreme WO stars. This matters because WR stars are progenitors of supernovae and black holes, so their true masses directly affect models of compact-object formation and cosmic feedback. Three physical processes likely contribute to the shortfall: stronger mass loss than assumed, inflated envelopes near the Eddington limit, and binary interaction channels that strip mass. Together these mechanisms plausibly explain the observed deficit. The method provides an independent, falsifiable tool for testing stellar-evolution models using data from upcoming large spectroscopic surveys.