XMM-Newton observations of ULIRGs I: A Compton-thick AGN in IRAS19254-7245

We present the XMM-Newton observation of the merging system IRAS 19254-7245, also known as The Superantennae, whose southern nucleus is classified as a Seyfert 2 galaxy. The XMM-Newton data have allowed us to perform a detailed X-ray imaging and spectral analysis of this system. We clearly detect, for the first time in this system, a strong (EW � 1.4 keV) Fe emission line at 6.49 ± 0.1 keV (rest-frame). The X-ray spectrum requires a soft thermal component (kT � 0.9 keV; L0.5−2 � 4×10 41 erg s −1 ), likely associated with the starburst, and a hard power-law continuum above 2 keV (observed L2−10 � 4 × 10 42 erg s −1 ). We confirm the flatness of this latter component, already noted in previous ASCA data. This flatness, together with the detection of the strong Fe-Kline and other broad band indicators, suggest the presence of a Compton-thick AGN with intrinsic luminosity > 10 44 erg s −1 . We show that a Compton-thick model can perfectly reproduce the X-ray spectral