= Accretion-disk boundary layer
{title2=$T_{\rm BL},\ L_{\rm BL}$}
An accretion-disk boundary layer connects nearly <Keplerian rotation> to a stellar surface rotating at a different angular speed. For a slowly rotating star, dissipation of the incoming orbital <kinetic energy> gives $L_{\rm BL}\simeq GM\dot M/(2r_*)$, comparable to the <standard thin-disk luminosity>. If the emitting area scales as $r_*H$, its <blackbody> <effective temperature> scales as $T_{\rm BL}\sim(r_*/H)^{1/4}T_{\rm in}$. The coefficient depends on geometry, and stellar rotation reduces the available energy.
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