Resolving the substructures in the disc around the o type protostar G17.64

Using the ALMA long baselines at band 6 we probe scales below 50au for G17.64. We fully resolve the dust disc thats is only 120au in radii, but also find arc or ring substructures in the dust. This is the first detection of such structures in a massive O type source. We also detect the vibrational water line that shows keplerian rotation, pointing to a 45Mo source. We discuss our findings and the possible nature of the substructures after Toomre Q stability analysis