1994A&A...290..133V

We have derived absolute visual magnitudes for 18 low-mass X-ray binaries using various methods (membership of a stellar system with known distance, Eddington luminosity X-ray standard candle, and absolute magnitude of the secondary star). A simple model for the optical emission is presented in which the X rays from the central source are reprocessed in an accretion disk of standard shape; this model implies that the optical luminosity, L_V, scales with the X-ray luminosity, L_X, and the outer radius of the accretion disk, R, approximately as L_V∝L_X^1/2R. The absolute visual magnitudes of active low-mass X-ray binaries are found to range between ∼5 and ~-5. This large range is the consequence of the large range in the X-ray luminosity and size of the accretion disk.