SIMBAD references

We present the detailed analysis of the X-ray data for 6 pairs, isolated or in poor groups, observed at high resolution with the ROSAT HRI . In all cases, the stronger X-ray source is associated with the brighter early-type member and is extended. The extent varies from galactic to group scale, from 3 (RR 210b) to 182kpc( RR 22a). The fainter members are detected only in two pairs, RR 210 and RR 259. Except for one case, no significant substructures have been detected in the X-ray maps, possibly also as a consequence of the poor statistics. The core radii of the X-ray surface brightness profiles are in the range 1-3kpc. The distribution of the luminosities of galaxies in pairs encompasses a very wide range of both luminosities and L_X/L_B ratios, in spite of the very small number of objects studied so far. Our data provide no evidence that pair membership affects the X-ray properties of galaxies. Observation are discussed in the context of the pair/group evolution.