= Projected mass lower bound for a bound point-mass orbit
{title2=$\mu>v_{\rm los}^2R_\perp/2$}
For a bound <Kepler orbit>, specific <orbital energy> $v^2/2-\mu/r$ is negative. Therefore $\mu>v^2r/2$. A projected separation $R_\perp\le r$ and a systemic-motion-corrected line-of-sight speed $|v_{\rm los}|\le v$ give the displayed lower bound. One position and one spectral <velocity> already constrain the mass in this model; a fitted orbit gives much more. The bound assumes a bound orbit in a point-mass potential; it is not an unrestricted enclosed-mass formula for an arbitrary extended potential.
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