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

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1. Introduction

Soon after it was discovered that the X-ray spectra of Seyfert 1 galaxies can be described at 0-th order by a simple power-law (Mushotzky 1984), it became clear that significant deviations exist from this simple behavior. In particular, a soft excess above the extrapolation of the high-energy power-law was observed by all the main X-ray missions in the 80s: HEAO-1 (Pravdo et al. 1981; Singh et al. 1985), EXOSAT (Arnaud et al. 1985; Turner & Pounds 1989), Einstein (Kruper et al. 1990; Turner et al. 1990), BBXRT (Turner et al. 1993). Optical/UV and soft X-ray emissions are generally well correlated (Walter & Fink 1993; Puchnarewicz et al. 1996; Laor et al. 1997) and this has traditionally supported the idea that they are one and the same spectral component, probably originating as thermal emission in an accretion disk (Czerny & Elvis 1987). However, thin disc models generally fail to reproduce the observed Spectral Energy Distribution (SED, Ulrich & Molendi 1996; Laor et al. 1997). Moreover, the tight correlation between optical and UV variations in some Seyfert galaxies (Peterson et al. 1991, Clavel et al. 1991) argues against an origin as a thermal emission from accretion discs. If irradiation of the disc by a high-energy external source is taken self-consistently into account, the agreement between data and models improves (Molendi et al. 1992, Siemiginowska et al. 1995). There is nowadays formidable evidence that reprocessing of the primary radiation indeed occurs on µpc scale around the nuclei of Seyfert 1s, either from neutral (Pounds et al. 1990, Piro et al. 1990, Nandra & Pounds 1994, Nandra et al. 1997a) or ionized (Piro et al. 1997) matter.

Given this framework, we discuss in this paper the results of a Beppo-SAX observation of the radio-quiet AGN 1H0419-577 (1ES 0425-573), along with the analysis of a still unpublished pointed PSPC observation, which was performed four years earlier. 1H0419-577 is classified as a Seyfert 1 by Brissenden (1989) and as a Seyfert 1.5 by Grupe (1996). A high-quality optical spectrum was taken the same night as the Beppo-SAX observation, and the relevant results are presented in this paper.

1H0419-577 is a moderately distant ([FORMULA]) object. It is one of the brightest extragalactic sources in the EUVE catalog, with flux [FORMULA] erg cm-2 s-1 in the 58-174 Å band (Marshall et al. 1995, Fruscione 1996). It is also included in the Seyfert soft X-ray selected sample of Grupe et al. (1998, RXJ0426-57). No significant radio emission is reported, the upper limit on the 8.4 GHz flux being 3.6 mJy (Brissenden 1989). Despite the fact that it is a relatively bright source in X-ray (it was detected by HEAO A-2, Mushotzky 1995, private communication), its X-ray properties have not been well studied yet.

The paper is organized as follows: in Sect. 2 the optical data are presented. Reduction and analysis of the Beppo-SAX data are presented in Sect. 3 and Sect. 4 respectively. In Sect. 5 the PSPC data are analyzed and the relevant outcomes are compared with Beppo-SAX ones. The discussion of the main results is given in Sect. 6. Sect. 7 summarizes the main conclusions. [FORMULA] km s-1 Mpc-1 is assumed throughout the paper. Preliminary results have been published in Guainazzi et al. (1998).

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© European Southern Observatory (ESO) 1998

Online publication: October 21, 1998