THE SU-URSA-MAJORIS STAR CU-VELORUM - PHYSICAL PARAMETERS, DOPPLER IMAGING AND PHOTOMETRIC TIME-SERIES

Time resolved Ha spectroscopy and differential photometry at the U, B bands, reveal an orbital period of 1.(h)884 +/- 0.(h)005 and a K radia l velocity semiamplitude of 49 +/- 6 km s(-1). The dynamical solution and spectroscopic measures indicate a mass ratio M(2)/M(1) = 0.115 +/- 0.005, a primary mass M(1) = 1.23 +/- 0.23 M., a secondary mass M(2) = 0.15 +/- 0.03 M. and an inclination angle i = 59 degrees +/- 6 degre es. Doppler imaging reveals a line emissivity decreasing with radius a s r(-1.4). Smooth 0.(m)11 semiamplitude periodic oscillations at U and B bands, H alpha V/R variations and equivalent width oscillations up to 15 % of the mean value, could be due to a hotspot located in the st ream-disk impact region. This picture is supported by the H alpha Dopp ler tomogram.