 Minimum companion mass from radial velocity

For a companion of negligible mass compared with its host, $M_p\sin i=K[P/(2\pi G){]}^{1/3}{M}_{\star }^{2/3}\sqrt{1-e^2}$. The observable supplies a projected mass; the minimum at a specified eccentricity occurs for an edge-on orbit. A exoplanet transit can constrain inclination, while low-inclination stars or brown dwarfs can otherwise mimic a lower-mass companion. The exact relation retains $(M_{\star }+M_p{)}^{2/3}$ in the denominator.