The magnitudes of some general relativistic effects depend on the mass of gravitating objects; therefore, these effects can be used for the stellar mass measurement. Several methods have been proposed; for example, the microlensing effect (Paczyński 1986), and the parallactic variation of gravitational deflection of the light from the source (Hosokawa et al. 1993).
Recently some candidates for MACHOs – a kind of dark matter candidates in the Galactic halo – have been discovered by their microlensing effect, and their masses were estimated to be of the order of 0.1M
ʘ, under many assumptions. Actual measurement of MACHO masses are important in specifying what kind of object the MACHO is.