High-resolution spectroscopy of the intermediate polar EX Hydrae II. The inner disk radius

EX Hya is one of the best studied, but still enigmatic intermediate polars. We present phase-resolved blue VLT/UVES high-resolution (lambda/Delta lambda similar or equal to 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 vertical bar upsilon(rad)vertical bar similar or equal to 1200 km s(-1), defining the inner edge of the accretion disk at r(in) similar or equal to 7 x 10(9) cm or similar to 10R(1) (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) similar to 1R(1) that is required by X-ray and optical observations. Our results contradict models that advocate a small magnetosphere and a small inner disk hole. Equating r(in) with the magnetospheric radius in the orbital plane allows us to derive a magnetic moment of the WD of mu(1) similar or equal to 1.3 x 10(32) G cm(3) and a surface field strength B-1 similar to 0.35 MG. Given a polar field strength B-p less than or similar to 1.0 MG, optical circular polarization is not expected. With an accretion rate (M) over dot = 3.9 x 10(-11) M-circle dot yr(-1), the accretion torque is G(acc) similar or equal to 2.2 x 10(33) g cm(2) s(-2). The magnetostatic torque is of similar magnitude, suggesting that EX Hya is not far from being synchronized. We measured the orbital radial-velocity amplitude of the WD, K-1 = 58.7 +/- 3.9 km s(-1), and found a spin-dependent velocity modulation as well. The former is in perfect agreement with the mean velocity amplitude obtained by other researchers, confirming the published component masses M-1 similar or equal to 0.79 M-circle dot and M-2 similar or equal to 0.11 M-circle dot.