Arp 299: a second merging system with two active nuclei?

Arp 299 is a powerful far-IR merging starburst system, composed of IC 694 and NGC 3690. Recent BeppoSAX observations clearly unveiled the presence of a strongly absorbed (N_H~=2.5×10²⁴ cm^-2) AGN, but at the spatial resolution of BeppoSAX instruments the system was not resolved. Here we present the XMM-Newton observations of Arp 299, which allow us to disentangle the X-ray emission of the two merging galaxies. The detection in both spectra of a hard X-ray emission and of a strong line-like structure in the 6.4-6.7 keV energy range seems to suggest the presence of an AGN in both nuclei. This would be the second discovery of two AGNs in a merging system after NGC 6240 [ApJL 582 (2003) L15].