Precision Fe Kalpha and Fe Kbeta Line Spectroscopy of the Seyfert 1.9 Galaxy NGC 2992 with Suzaku

We present detailed time-averaged X-ray spectroscopy in the 0.5--10 keV bandof the Seyfert~1.9 galaxy NGC 2992 with the Suzaku X-ray Imaging Spectrometers(XIS). We model the complex continuum in detail. There is an Fe K line emissioncomplex that we model with broad and narrow lines and we show that theintensities of the two components are decoupled at a confidence level >3sigma.The broad Fe K line has an EW of 118 (+32,-61) eV and could originate in anaccretion disk (with inclination angle greater than ~30 degrees). The narrow FeKalpha line has an EW of 163 (+47,-26) eV and is unresolved FWHM <4090 km/s)and likely originates in distant matter. The absolute flux in the narrow lineimplies that the column density out of the line-of-sight could be much higherthan measured in the line-of-sight, and that the mean (historically-averaged)continuum luminosity responsible for forming the line could be a factor ofseveral higher than that measured from the data. We also detect the narrow FeKbeta line with a high signal-to-noise ratio and describe a new robust methodto constrain the ionization state of Fe responsible for the Fe Kalpha and FeKbeta lines that does not require any knowledge of possible gravitational andDoppler energy shifts affecting the line energies. For the distantline-emitting matter (e.g. the putative obscuring torus) we deduce that thepredominant ionization state is lower than Fe VIII (at 99% confidence),conservatively taking into account residual calibration uncertainties in theXIS energy scale and theoretical and experimental uncertainties in the Fe Kfluorescent line energies. From the limits on a possible Compton-reflectioncontinuum it is likely that the narrow Fe Kalpha and Fe Kbeta lines originatein a Compton-thin structure.Comment: Abstract is abridged. Accepted for publication in the Suzaku special issue of PASJ (November 2006). 18 pages, 6 figure