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Astron. Astrophys. 339, 327-336 (1998)

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7. Summary

We report on the first simultaneous X-ray and optical observations of the radio-quiet AGN 1H0419-577. The main results can be summarized as follows:

(1) the optical spectrum points unambiguously to a classification as a Seyfert 1.

(2) 1H0419-577 is detected in X-rays up to 40 keV. The whole 1.8-40 keV spectrum is well modeled by a simple power-law with a rather flat ([FORMULA]) spectral index.

(3) No iron emission line or Compton reflection by an X-ray illuminated neutral disc are required by the data. However, the constraints on the spectral parameters are not so tight to rule out the possibility that this object follows the trend of high luminosity Seyferts to have fainter and/or ionized iron lines and Compton continua.

(4) The SED of the simultaneous optical and X-rays observations peaks apparently around 3500-4000Å, as typically observed in RQQ (Laor et al. 1997).

(5) The comparison with a 1992 ROSAT and a pair of 1996 ASCA observations (Turner et al. 1998) reveals that the spectrum has undergone a transition between a soft ([FORMULA]) and a hard ([FORMULA]) state, at least in the 0.7-2 keV band. We have discussed in this paper two possible explanations for this behavior and their implications:

  • a remarkably variable ([FORMULA] half an order of magnitude in flux and/or effective temperature) soft X-ray excess, which should come along with a corresponding dynamics of the optical and UV emission, if the SED is dominated by a single BgB. The optical historical monitoring of this source, albeit sparse, seems to rule out this possibility;

  • a change of the primary continuum spectrum, which could be explained either as a transition from a Compton thick to a Compton thin regime in the disk-corona two-phase model of Haardt & Maraschi (1993) or a transition between a bulk to a thermal motion regime in a viscuosless two-phase shock accretion disc (Chakrabarti and Titarchuk 1995; Ebisawa et al. 1996).

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© European Southern Observatory (ESO) 1998

Online publication: October 21, 1998