Abstract
A detailed analysis of spectral and photometric observations led to the finding that the orbital period of UX~Mon is secularly decreasing and that the system is in a rare phase of fast mass transfer prior to the mass ratio reversal.
A detailed analysis of spectral and photometric observations led to the finding that the orbital period of UX~Mon is secularly decreasing and that the system is in a rare phase of fast mass transfer prior to the mass ratio reversal.