Complex resonance absorption structure in the X-ray spectrum of IRAS 13349+2438

The luminous infrared-loud quasar IRAS 13349+2438 was observed with the XMM-Newton Observatory as part of the Performance Verification program. The spectrum obtained by the Reflection Grating Spectrometer (RGS) exhibits broad (v similar to 1400 km s(-1) FWHM) absorption lines from highly ionized elements including hydrogen- and helium-like carbon, nitrogen, oxygen, and neon, and several iron L-shell ions (FeXVII XX). Also shown in the spectrum is the first astrophysical detection of a broad absorption feature around lambda = 16-17 Angstrom identified as an unresolved transition array (UTA) of 2p-3d inner-shell absorption by iron M-shell ions in a much cooler medium; a feature that might be misidentified as an O VII edge when observed with moderate resolution spectrometers. No absorption edges are clearly detected in the spectrum. We demonstrate that the RGS spectrum of IRAS 13349+2438 exhibits absorption lines from at least two distinct regions, one of which is tentatively associated with the medium that produces the optical/UV reddening.