= Radiative shift of an isothermal breeze maximum
{title2=$r'_M=[GM-\sigma L/(4\pi\bar m c)]/(2a^2)$}
For unattenuated isotropic radiation from a point source, the <radiation pressure> force on each absorbing particle is $\sigma L/(4\pi cr^2)$. Dividing by its <mass> $\bar m$ changes the effective inverse-square inward acceleration to $[GM-\sigma L/(4\pi\bar m c)]/r^2$. The wind equation therefore places the maximum of a <subsonic isothermal breeze> at the displayed radius, provided the bracket is positive. If it is nonpositive, the positive-temperature subsonic outflow decreases in speed throughout its domain and has no interior speed maximum. A cross section per particle requires that particle's mass; an <opacity> per unit mass instead absorbs this conversion.
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