Accretion-powered effective-temperature scaling ($T_{\mathrm{eff}}\propto t^{1/4}$)

For constant supply, negligible seed mass and fixed emitting radius, $M=\dot{M}t$ and $L_{\mathrm{acc}}\propto t$. Thermal emission with $L=4\pi r_0^2{\sigma }_{\mathrm{SB}}{T}_{\mathrm{eff}}^4$ therefore gives the quarter-power law. It describes an effective surface temperature. A homologous ideal-gas interior at the same fixed radius instead has virial temperature proportional to mass and hence to time; its absolute temperature requires a structural model.