A coordinated campaign on the intermediate polar AE Aqr .1. The system parameters

We report intermediate-resolution spectroscopy (50 km s(-1)) of the magnetic cataclysmic variable AE Aqr performed as part of the World Astronomy Days (WAD) campaign. Our analysis of the absorption features supports a K4 classification for the companion star, which contributes greater than or equal to 95 per cent of the total flux in the range 600-700 nm. We find that the companion star fills its Roche lobe since we detect a 10 per cent modulation in the rotational broadening (V sin i) of the absorption lines, arising from the changing geometry. Model fitting to the V sin i (phi) curve enables us to measure directly the system inclination (i = 58 +/- 6 degrees) and the gravity darkening coefficient (beta = 0.08 +/- 0.01). Improved orbital parameters are also presented, including an updated mass ratio (q = K-1/K-2 = 0.630 +/- 0.012) based upon our K-2 value and the spin-pulse delay. An independent determination of q is also provided by correcting the phase-averaged V sin i for non-spherical effects, The need for these two values to agree constrains the limb-darkening coefficient to be epsilon similar or equal to 0.40 (for beta = 0.08), The component masses derived from our values of K-2, q and i are M(1) = 0.79 +/- 0.16 M(.) and M(2) = 0.50 +/- 0.10 M(.). In addition, we do not see spectral evidence of irradiation effects.