We present XMM-Newton observations of two hyperluminous IRAS galaxies ( L _ { Bol } > 10 ^ { 13 } h _ { 50 } ^ { -2 } \thinspace L _ { \odot } ) , 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 \simeq 0.3 keV and L ( 0.5 - 2.0 { { \thinspace keV } } ) = 2.1 \times 10 ^ { 42 } { \thinspace erg } { \thinspace s } ^ { -1 } .
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 { { \thinspace keV } } ) \gtrsim 1.8 \times 10 ^ { 44 } { \thinspace erg } { \thinspace s } ^ { -1 } .
Comparison with the infrared power requires that the X-ray reflector subtend \sim 2 \pi / 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 < 2 \pi / 5 sr .
The direct lines of sight to the AGN in both objects are Compton-thick ( N _ { H } > 1.5 \times 10 ^ { 24 } { \thinspace cm } ^ { -2 } ) , 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 .