More than 50 years after the dawn of X-ray astronomy , the dynamical parameters of the prototypical X-ray binary Sco X-1 are still unknown .
We combine a Monte Carlo analysis , which includes all the previously known orbital parameters of the system , along with the K-correction to set dynamical constraints to the masses of the compact object ( M _ { 1 } < 1.73 M _ { \odot } ) and the companion star ( 0.28 M _ { \odot } < M _ { 2 } < 0.70 M _ { \odot } ) .
For the case of a canonical neutron star mass of M _ { 1 } \sim 1.4 M _ { \odot } , the orbital inclination is found to be lower than 40 ^ { \circ } .
We also present the best near-infrared spectrum of the source to date .
There is no evidence of donor star features on it , but we are able to constrain the veiling factor as a function of the spectral type of the secondary star .
The combination of both techniques restricts the spectral type of the donor to be later than K4 and luminosity class IV .
It also constrains the contribution of the companion light to the infrared emission of Sco X-1 to be lower than 33 % .
This implies that the accretion related luminosity of the system in the K band is larger than \sim 4 \times 10 ^ { 35 } erg s ^ { -1 } .