radiant flux

Radiant flux (often symbolized φ_e) the rate of energy (power) emitted/radiated by something, e.g., joules per second, aka, watts. Spectral flux (φ_e,ν or φ_e,λ) is the radiant power per frequency or wavelength. The above terms are common in sciences other than astrophysics, in which the term luminosity is often used for an astronomical object's (e.g., a star's) radiant flux.