The water megamaser in the merger system Arp299
  We present preliminary results of an interferometric study of the water megamaser in the merger system Arp299. This system is composed of two main sources: IC694 and NGC3690. There is clear evidence that most of the water maser emission is associated with the nucleus of the latter, confirming the presence of an optically obscured AGN as previously suggested by X-ray observations. Furthermore, emission arises from the inner regions of IC694, where an OH megamaser is also present. The velocity of the water maser line is blueshifted w.r.t. the optically determined systemic velocity and is consistent with that of the OH megamaser line. This finding might then indicate that both masers are associated with the same (expanding) structure and that, for the first time, strong 22 GHz water and 1.67 GHz OH maser emission has been found to coexist. 
A. Tarchi, P. Castangia, C. Henkel and K. M. Menten