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Astron. Astrophys. 351, 893-902 (1999)

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

J. Siebert, S. Komossa and W. Brinkmann

Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, 85740 Garching, Germany

Received 29 June 1999 / Accepted 6 October 1999


IRAS 13349+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 IRAS 13349+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 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 variable and/or complex warm absorber, a variable soft X-ray continuum and instrumental effects.

Key words: galaxies: active – galaxies: quasars: individual: IRAS 13349+2438 – X-rays: galaxies

Correspondence to: J. Siebert (jos@mpe.mpg.de)

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© European Southern Observatory (ESO) 1999

Online publication: November 16, 1999