The Eddington Luminosity Limit for Multiphased Media

We consider the effective Eddington luminosity in a locally inhomogeneous medium by averaging out the coarse, small scale behavior. We show that the ratio between the emitted flux and the average radiation force changes. The mean luminosity can therefore theoretically exceed the classical Eddington limit. It is further shown that acoustic modes are unstable under most relevant conditions, and they unavoidably grow in such a way that they change the effective limiting Eddington luminosity. The instability and the increased limiting luminosity can explain the observed super Eddington luminosity phenomenon in novae. Subject headings: Radiative transfer --- novae, cataclysmic variables To Appear in ApJ Letters 1. Introduction: The Specific Astrophysical Problem and Set-up The best studied example of systems exhibiting super Eddington luminosities is undoubtedly novae. These stars increase their luminosities by factors of 10 4 or more within a few hours and stay in this peak luminosity f...