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

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1H0419-577: a "two-state" soft X-ray Seyfert galaxy *

M. Guainazzi 1, 2, A. Comastri 3, G.M. Stirpe 3, W.N. Brandt 4, F. Fiore 5, 2, K.M. Leighly 6, G. Matt 7, S. Molendi 8, E.M. Puchnarewicz 9, L. Piro 10 and A. Siemiginowska 11

1 Astrophysics Division, Space Science Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
2 Beppo-SAX Science Data Center, c/o Nuova Telespazio, Via Corcolle 19, I-00131 Roma, Italy
3 Osservatorio Astronomico di Bologna, Via Zamboni 33, I-40126 Bologna, Italy
4 Department of Astronomy and Astrophysics, Penn State University, 525 Davey Lab, University Park, PA 16802, USA
5 Osservatorio Astronomico di Roma, Via dell'Osservatorio 5, I-00040 Monteporzio-Catone (RM), Italy
6 Columbia Astrophysical Laboratory, Columbia University, 538 West 120th Street, New York, NY 10027, USA
7 Dipartimento di Fisica, Università degli Studi "Roma 3", Via della Vasca Navale 84, I-00146 Roma, Italy
8 Istituto di Fisica Cosmica e Tecnologie Relative/C.N.R., Via Bassini 15, I-20133 Milano, Italy
9 Mullard Space Science Laboratory, University College London, Holmbury St.Mary, Dorking, Surrey RH5 6NT, UK
10 Istituto di Astrofisica Spaziale - C.N.R., Via Fosso del Cavaliere, I-00133 Roma, Italy
11 Harvard-Smithsonian Center for Astrophysics,60 Garden St., Cambridge, MA 02138, USA

Received 4 March 1998 / Accepted 15 July 1998


In this paper we report on the first simultaneous optical and X-ray (Beppo-SAX) observations of the radio-quiet AGN 1H0419-577. The optical spectrum clearly leads us to classify this source as a Seyfert 1. The X-ray spectrum is, however, somewhat at odds with this classification: a simple flat ([FORMULA]) and featureless power-law is a good description of the whole 1.8-40 keV spectrum, even if the upper limit to a broad iron line is not very tight. An analysis of a still unpublished ROSAT observation of the same target reveals that the soft X-ray spectrum has undergone a transition from a steep ([FORMULA]) to a flat ([FORMULA]) state, at least in the 0.7-2 keV band. If this difference is due to a remarkably variable soft excess, it is unlikely that a single component is responsible for the optical/UV/soft X-ray spectral distribution. The hypothesis that the difference is due to a change in the primary X-ray continuum and its implications for current Comptonization models are discussed.

Key words: X-rays: galaxies – galaxies: Seyfert – galaxies: individual: 1H0419-577

* Partly based on observations collected at the European Southern Observatory, La Silla, Chile

Send offprint requests to: M. Guainazzi, (mguainaz@astro.estec.esa.nl)

© European Southern Observatory (ESO) 1998

Online publication: October 21, 1998