Radio galaxies in cooling core clusters. Renewed activity in the nucleus of 3C 317?

We present the results of VLBA observations of the radio galaxy 3C 317, associated with the cD galaxy UGC 09799 at the centre of the cooling core cluster of galaxies A2052. These observations were carried out at 1.7 GHz, 4.9 GHz and 8.3 GHz, in polarimetric mode, and allowed us to image the parsec scale region of the source. Our analysis suggests that the nucleus of 3C 317 hosts a very young radio source. The estimated radiative age for the radio structure within the inner 10 pc is similar to170 yr. Given the existence of extended radio emission on the arcsecond scale, we suggest that 3C 317 is a restarted radio galaxy. The implications of this result in the light of the interaction between radio plasma and thermal hot gas in clusters of galaxies are briefly discussed.