The warm absorber in IRAS 13349+2438: dusty or not?

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IRAS13349+2438 was the first quasar suggested to host a warm absorber with internal dust. We obtained new HRI data for this object and derive constraints on the X-ray emitting region of IRAS13349+2438 by investigating its X-ray extent and lightcurve. Rapid X-ray variability is detected with a factor of two change in count rate within one day and 20% variability within about three hours, which practically rules out any significant contribution of scattered X-rays. We present for the first time a detailed, self-consistent modeling of the ROSAT PSPC and ASCA spectrum of IRAS13349+2438 in terms of a warm absorber including dust. It turns out that both a dust-free and a dusty single-component warm absorber fail to explain the ROSAT, ASCA, and optical data simultaneously. We discuss possible explanations such as a variable and/or complex warm absorber, a variable soft X-ray continuum and instrumental effects.