= Stellar thermal equilibrium
{title2=$L_{\rm surface}=L_{\rm heat}-L_\nu$}
In <stellar structure>, stellar thermal equilibrium means that internal heating balances the surface <luminosity> and any energy loss through neutrinos, with negligible secular storage of thermal <energy> on the timescale considered. A star can satisfy this balance while its interior is hotter than its surface and <heat> flows outward. It is therefore different from equal-temperature <thermal equilibrium> between systems. Neglecting neutrino losses, the balance is $L_{\rm surface}=L_{\rm heat}$. In a slowly mass-losing <donor star>, a <stellar thermal equilibrium> radius sequence applies only when thermal adjustment is fast compared with the mass-loss timescale; rapid loss instead requires the adiabatic <stellar radius response exponent>.
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