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A study on the intermediate polar EX Hya is presented, based on simultaneousphotometry and high dispersion spectroscopic observations, during fourconsecutive nights. The strong photometric modulation related to with the67-min spin period of the primary star is clearly present, as well as thenarrow eclipses associated to the orbital modulation. Since our eclipse timingshave been obtained almost 91,000 cycles since the last reported observations,we present new linear ephemeris, although we cannot rule out a sinusoidalvariation suggested by previous authors. The system mainly shows double-peakedH$\alpha$, H$\beta$ and HeI $\lambda$5876 \AA emission lines. From the profileof the H$\alpha$ line, we find two components; one with a steep rise andvelocities not larger than $\sim$1000 km s$^{-1}$ and another broader componentextending up to $\sim$2000 km s$^{-1}$, which we interpret as coming mainlyfrom the inner disc. A strong and variable hotspot is found and a stream-likestructure is seen at times. We show that the best solution correspond to $K_1 =58 \pm 5$ km s$^{-1}$ from H$\alpha$, from the two emission components, whichare both in phase with the orbital modulation. We remark on a peculiar effectin the radial velocity curve around phase zero, which could be interpreted as aRositter-MacLaughlin-like effect, which has been taken into account beforederiving $K_1$. This value is compatible with the values found inhigh-resolution both in the ultraviolet and X-ray. We find: $M_{1} = 0.78 \pm0.03$ M$_{\odot}$, $ M_{2} = 0.10 \pm 0.02$ M$_{\odot}$ and $a = 0.67 \pm 0.01$R$_{\odot}$. Doppler Tomography has been applied, to construct six Dopplertomograms for single orbital cycles spanning the four days of observations tosupport our conclusions. Our results indicate that EX Hya has a well formeddisc and that the magnetosphere should extend only to about$3.75\,R_{\rm{WD}}$.

A Radial Velocity Study of the Intermediate Polar EX Hydrae