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

IRAS 13349+2438 was the first quasar suggested to host a warm absorber with internal dust, We obtained new MI data for this object and derive constrai nts on the X-ray emitting region of IRAS 13349+2438 by investigating its X- ray extent and lightcurve. Rapid X-ray variability is detected with a facto r of two change in count rate within one day and 20% variability within abo ut three hours, which practically rules out any significant contribution of scattered X-rays. We present for the first time a detailed, self-consisten t modeling of the ROSAT PSPC and ASCA spectrum of IRAS 13349+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 var iable and/or complex warm absorber, a variable soft X-ray continuum and ins trumental effects.