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

Abstract

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 ( 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 Åidentified 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 Ovii 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.