1998A&A...330..823S

We present ROSAT observations of the starburst galaxy NGC 2782 (HRI plus a weak PSPC frame) and the ultraluminous infrared galaxy NGC 6240 (PSPC). The (0.1-2.4)keV spectra of both objects appear similar. However, due to better sampling spectral modeling is only warranted in case of NGC 6240 for which both a single thermal Raymond-Smith model (kT=0.44±0.15keV) or a hybrid model consisting of 80% power-law with the canonical photon index -1.9 plus 20% Raymond-Smith contribution (kT=0.63±0.35keV) lead to good fits. However, the single thermal model turns out to be unlikely because it yields a luminosity of 3.8x10⁴³erg/s, which is hard to reach in a starburst superwind-scenario. The hybrid model leads to a more moderate luminosity of 5.2x10⁴²erg/s, of which 1.0x10⁴²erg/s can be attributed to shocked superwind gas. We link the remaining 4.2x10⁴²erg/s powerlaw to an AGN component because the alternative of inverse-compton scattering of the FIR radiation leads to a too low flux when estimated with available data. The result appears to be consistent with preliminarily announced ASCA observations. For NGC 2782 we find L_x(0.1-2.4keV)=4x10⁴¹erg/s (within a factor of four) which can be explained by emission from a shocked superwind region with a high preshock density in agreement with earlier optical evidence for an outflowing supershell.