EX Hya spectra

We present phase-resolved blue VLT/UVES high-resolution ({lambda}/{DELTA}{lambda}~=16.000) spectra of EX Hya taken in January 2004. Our analysis involves a unique decomposition of the Balmer line profiles into the spin-modulated line wings that represent streaming motions in the magnetosphere and the orbital-phase modulated line core that represents the accretion disk.

Spectral analysis and tomography show that the division line between the two is solidly located at |v_rad_|~=1200km/s, defining the inner edge of the accretion disk at r_in_=~7x10^9^cm or ~10R1 (WD radii). This large central hole allows an unimpeded view of the tall accretion curtain at the lower pole with a shock height up to h_sh_~1R1 that is required by X-ray and optical observations. Our results contradict models that advocate a small magnetosphere and a small inner disk hole.