Abstract

Aims. AD Men has been 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 observations presented here we aim to clarify its nature. Methods. Time-resolved photometry and spectroscopy has been used to obtain information on the orbital period of this system. Results. The light curve shows the typical flickering and a clear hump-like periodic modulation with an average amplitude of 0.3 mag and a period of P = 2.20(02) h. The radial velocity measurements of the Hα emission line confirm this value as the orbital period. Conclusions. 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. © ESO 2006.