What is the major limitation when calculating the mass of components in a purely spectroscopic binary system?
Answer
The inclination ($i$) of the orbit is usually unknown, leading to only a minimum mass ($M \sin^3 i$).
Because only the velocity component along the line of sight ($v \sin i$) is measured, if the inclination is not known (i.e., if the orbit is not edge-on), the resulting mass calculation is only a lower limit, expressed as $M \sin^3 i$.
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