AD Men was classified as a probable long-period dwarf nova based on its
long-term variability. Recent spectroscopic data instead suggested a
short-period system. With the here presented observations we aim at clarifying
its nature. Time--resolved photometry and spectroscopy has been used to get
information on the orbital period of this system. The light curve shows the
typical flickering and a clear hump--like periodic modulation with an average
amplitude of 0.3mag and a period of P=2.20(02)h. The radial velocity
measurements of the Halpha emission line confirm this value as the orbital
period. AD Men is thus located at the lower end of, but clearly inside, the gap
of the period distribution of cataclysmic variables, making it one of only 11
dwarf novae in this important period range.Comment: 5 pages, 6 figures, accepted by A&
