PX285 - F3 - spectroscopic binaries

evidence of binarity in the spectra, such as two sets of absorption lines, or doppler shift of absorption lines
motion of stars causes a doppler shift of absorption lines

\begin{matrix} \frac{Δ λ}{λ} = \frac{v}{c} \\ v_{1, 2} = \frac{2 π r_{1, 2}}{P} \\ v_{1} + v_{2} = \frac{2 π}{P} (r_{1} + r_{2}) \\ ∴ M_{1} + M_{2} = \frac{P}{2 π G} (v_{1} + v_{2})^{3} \end{matrix}

where, $P$ is the orbital period

M_{1} + M_{2} = \frac{P}{2 π G} {(\frac{v_{1, r} + v_{2, r}}{\sin i})}^{3}