Spectroscopy of AGN-dominated ULIRGs: NGC 6240

NGC 6240 is a known ULIRG which is unique among such objects because its Xrayspectrum is very similar to those of many Seyfert 2s yet its IR spectrum showsno indication of gas excitation by a nonthermal source. Thus, there is a bigquestion regarding the major energy source with important implications to theXray background and the AGNstarburst connection. We propose 100 ks XMMobservations to reveal the nature of this source and show how a good S/N RGSspectrum containing 1015 measurable lines, combined with a stateoftheartanalysis, can probe the physical state of the soft Xray gas and supplyinformation about its excitation by a starburs, an AGN source, or both. MOS andPN observations will define the SED and resolve the complex emissionabsorption feature near 68 keV. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]