The SU UMa star TU Mensae.

Photometric and spectroscopic observations of the SU UMa star TU Men during a superoutburst in Nov. 1980 are presented and analysed. The lightcurves are dominated by superhumps with a variable period (P_s ≅ 3^h, P_s < 0). The analysis of the spectra yields a periodic variability of the radial velocities with the orbital period P₀ ≅ 2^h50^m (amplitude: K₁ ≅ 150 km s^-1) and a variation of γ with the period U ≅ 2^d (amplitude: K_&gamma; ≅ 280 km s^-1). A primary mass M₁ ≅ 0.6 M_sun;, a mass ratio of q = M₁/M₂ ≅ 1.7 and an orbital inclination of i ≅ 65° are estimated. By fitting the observed Balmer absorption lines to theoretical line profiles for the accretion disk, a mass transfer rate of M≅ 6×10¹⁷ g s^-1 and a distance of 270 pc are obtained. An empirical relation between orbital period P₀ and superhump period P_s is given.