VLBI OBSERVATIONS OF HI ABSORPTION IN THE HIGHLY LUMINOUS GALAXY NGC-5793

H I absorption associated with NGC 5793 has been observed with four stations of the European VLBI network. The maximum antenna spacing of about 2000 km yielded an effective beamwidth of 0.030 arcsec. The observations show for the first time that, at 21-cm wavelength, the radio nucleus of NGC 5793 consists of a small source, of size 0.016 arcsec, which is extended parallel to the minor axis of the galaxy (i.e. at position angle 60-degrees). The H I absorption ranges in heliocentric radial velocity from 3420 to 3590 km s-1. It contains three components with velocities centred on 3475, 3520 and 3560 km s-1. The first two are associated with Hi clouds located directly in front of the nucleus; the first cloud may be some distance from the nucleus and moving away from it at a velocity of 45 km s-1, while the second may be near the nucleus. The component at 3560 km s-1 is displaced about 0.04 arcsec to the southwest of the continuum centre. It may be associated with a gas flow out of the plane of the galaxy.