XMM-Newton observations of two hyperluminous IRAS galaxies: Compton-thick quasars with obscuring starbursts

We present XMM-Newton observations of two hyperluminous IRAS galaxies (LBol > 10h 50 L⊙), neither of which was previously detected by ROSAT. Published models of the infrared spectral energy distributions imply that a starburst and obscured quasar contribute equally to the power of each source. IRAS F12514+1027 (z = 0.30) is detected in 18.6 ks with 130 EPIC-pn counts over 0.2-12 keV. The soft X-ray spectrum exhibits thermal emission from the starburst, with T ≃ 0.3 keV and L(0.5 − 2.0 keV) = 2.1 × 10 erg s . With its Fe K-edge, the flat continuum above 2 keV is interpreted as cold reflection from a hidden AGN of intrinsic L(2 − 10 keV) & 1.8 × 10 erg s . Comparison with the infrared power requires that the X-ray reflector subtend ∼ 2π/5 sr at the central engine. IRAS F00235+1024 (z = 0.575) is not detected by the EPIC-pn in 15.9 ks; the limits imply that the starburst is X-ray weak, and (for the AGN) that any hard X-ray reflector subtend < 2π/5 sr. The direct lines of sight to the AGN in both objects are Compton-thick (NH > 1.5 × 10 cm ), and the presence of a reflection component in F12514+1027, but not in F00235+1024, suggests that the AGN in the latter object is more completely obscured. This is consistent with their Seyfert-2 and starburst optical spectra, respectively.