There is a mismatch between modelled and observed distributions of optical stars masses in BH LMXB .
Companion masses in BH LMXB are found in the mass range 0.1 - 1.6 M _ { \odot } with the peak at 0.6 M _ { \odot } .
The standard evolutionary scenarios require the donor mass distribution peaks to be at least \sim 1 M _ { \odot } to eject a massive envelope of the black hole progenitor .
Imperfect of the methods of optical stars masses determination may cause this difference .

Two common used approximations of real Roche lobe filling star as distortion sources have been tested .
On the one hand , there is the a approximation of real Roche lobe filling optical stars as sphere .
We tested rotational broadening of absorption lines based on an exact calculation of CaI \lambda 6439.075 \textup { \AA } absorption profiles in the spectra of Roche lobe filling optical stars .
There is overestimation of projected equatorial rotational velocity V _ { rot } \sin i and , accordingly , underestimation of mass ratio q = M _ { x } / M _ { v } in the spherical star model .
On the other hand , the approximation of a real Roche lobe filling star as disk with uniform local profile and linear limb darkening law is more rough .
In this case overestimation of projected equatorial rotational velocity V _ { rot } \sin i is \sim 20 \% .
Such overestimation of V _ { rot } \sin i can result in significant underestimation of mass ratio q = M _ { x } / M _ { v } at hight value of q = M _ { x } / M _ { v } .
Refined value of q does not affect the mass of a black hole , but the mass of an optical star has shrunk 1.5 times .
Hence , the masses of optical stars in BH LMXB must be corrected downward , despite the contradictions to the standard evolutionary scenarios .