XMM-Newton Detection of a Compton-thick AGN in the 1 Jy ULIRG/LINER F04103-2838

We report on the detection of Fe Kα emission in F04103-2838, an ultraluminous infrared galaxy [ULIRG; log (L_IR/L_⊙) >= 12] optically classified as a LINER. Previous Chandra observations suggested the presence of both a starburst and an active galactic nucleus (AGN) in this source. A deeper (~20 ks) XMM-Newton spectrum reveals an Fe Kα line at rest-frame energy ~6.4 keV, which is consistent with cold neutral iron. The best-fit spectral model indicates that the Fe Kα line has an equivalent width of ~1.6 keV. The hard X-ray emission is dominated by a Compton-thick AGN with an intrinsic 0.2-10 keV luminosity of ~10⁴⁴ ergs s^-1, while the soft X-ray emission is from ~0.1 keV gas attributed to the starburst. The X-ray spectrum of this source bears a striking resemblance to that of the archetypal luminous infrared galaxy NGC 6240, despite differences in merger state and infrared properties.