We present XMM-Newton X-ray observations of the interacting galaxy pairs NGC 7771/7770 & NGC 2342/2341 .
In NGC 7771 , for the first time we are able to resolve the X-ray emission into a bright central source ( L _ { X } \sim 10 ^ { 41 } { ~ { } erg~ { } s ^ { -1 } } ) , plus two bright ( L _ { X } > 10 ^ { 40 } { ~ { } erg~ { } s ^ { -1 } } ) ultraluminous X-ray sources ( ULXs ) located either end of the bar .
The soft emission of the central source is well-modelled by a two-temperature thermal plasma with kT =0.4/0.7 keV .
The hard emission is modelled with a flat absorbed power-law ( \Gamma \sim 1.7 , N _ { H } \sim 10 ^ { 22 } { ~ { } cm ^ { -2 } } ) , and this together with a low-significance ( 1.7 \sigma ) \sim 300 eV equivalent width emission line at \sim 6 keV are the first indications that NGC 7771 may host a low-luminosity AGN .
For the bar ULXs , a power-law fit to X-1 is improved at the 2.5 \sigma level with the addition of a thermal plasma component ( kT \sim 0.3 keV ) , while X-2 is improved only at the 1.3 \sigma level with the addition of a disc blackbody component with T _ { in } \sim 0.2 keV .
Both sources are variable on short time-scales implying that their emission is dominated by single accreting X-ray binaries ( XRBs ) .
The three remaining galaxies , NGC 7770 , NGC 2342 and NGC 2341 , have observed X-ray luminosities of 0.2 , 1.8 & 0.9 \times 10 ^ { 41 } { ~ { } erg~ { } s ^ { -1 } } respectively ( 0.3–10 keV ) .
Their integrated spectra are also well-modelled by multi-temperature thermal plasma components with kT =0.2–0.7 keV , plus power-law continua with slopes of \Gamma =1.8–2.3 that are likely to represent the integrated emission of populations of XRBs as observed in other nearby merger systems .
A comparison with other isolated , interacting and merging systems shows that all four galaxies follow the established correlations for starburst galaxies between X-ray , far-infrared and radio luminosities , demonstrating that their X-ray outputs are dominated by their starburst components .