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The internal velocity structure in the Hyades cluster as seen by Hipparcos iscompared with realistic N-body simulations using the NBODY6 code, whichincludes binary interaction, stellar evolution and the Galactic tidal field.The model allows to estimate reliably the accuracy of astrometric radialvelocities in the Hyades as derived by Lindegren et al. (2000) and Madsen etal. (2002) from Hipparcos data, by applying the same estimation procedure onthe simulated data. The simulations indicate that the current cluster velocitydispersion decreases from 0.35 km/s at the cluster centre to a minimum of 0.20km/s at 8 pc radius (2-3 core radii), from where it slightly increasesoutwards. A clear negative correlation between dispersion and stellar mass isseen in the central part of the cluster but is almost absent beyond a radius of3 pc. It follows that the (internal) standard error of the astrometric radialvelocities relative to the cluster centroid may be as small as 0.2 km/s for asuitable selection of stars, while a total (external) standard error of 0.6km/s is found when the uncertainty of the bulk motion of the cluster isincluded. Attempts to see structure in the velocity dispersion usingobservational data from Hipparcos and Tycho-2 are inconclusive.Comment: 12 pages, accepted by A&

Hyades dynamics fromN-body simulations: Accuracy of astrometric radial velocities from Hipparcos