We present an analysis of constraints on the companion mass for the Galactic microquasar GRS 1915+105 .
Using the known inclination angle and stability of the jet axis , we can rule out massive ( M _ { s } \ga 3 M _ { \sun } ) companions with orbital axes not aligned with the jet axis .
For an aligned orbital axis , we constrain the ratio of the stellar radius to the binary semi-major axis to be R _ { s } / a < 0.342 , based on the lack of X-ray eclipses .
We then show that these constraints together with the X-ray luminosity , approximate black hole mass , and observations of the X-ray absorbing column density towards GRS 1915+105 rule out accretion via stellar wind from a massive companion , implying that accretion occurs via Roche-lobe overflow .
In that case , the constraint on R _ { s } / a rules out any companion with M _ { s } > 19.4 M _ { \sun } for a black hole mass of M _ { BH } \simeq 30 M _ { \sun } .
The lack of significant X-ray reprocessing in the infrared from GRS 1915+105 also provides constraints on the mass and temperature range of a Roche-lobe-filling mass donor .