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Astron. Astrophys. 333, 31-37 (1998)


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BeppoSAX observations of narrow-line Seyfert 1 galaxies

I. Ton S 180

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

1 Osservatorio Astronomico di Bologna, Via Zamboni 33, I-40126 Bologna, Italy
2 Osservatorio Astronomico di Roma, Via dell'Osservatorio, I-00040 Monteporzio-Catone, Italy
3 SAX-Science Data Center, Nuova Telespazio, Via Corcolle 19, I-00131 Roma, Italy
4 Dipartimento di Fisica "E. Amaldi", Università degli Studi "Roma Tre", Via della Vasca Navale 84, I-00146 Roma, Italy
5 Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802, USA
6 Department of Astronomy, Columbia University, 538 West 120th Street, New York, NY 10027, USA
7 Istituto di Astrofisica Spaziale - C.N.R., via E. Fermi 21, I-00044 Frascati, Italy
8 Istituto di Fisica Cosmica e Tecnologie Relative - C.N.R., via Bassini 15, I-20133 Milano, Italy
9 Astrophysics Division, Space Science Department of ESA ESTEC/SA, 2200 AG Noordwijk, The Netherlands
10 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA
11 Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK

Received 9 September 1997 / Accepted 9 December 1997

Abstract

We report on the first spectrum up to 10 keV of the bright narrow-line Seyfert 1 galaxy Ton S 180, obtained with the imaging instruments onboard BeppoSAX. This is the first observed source in a sample of a dozen narrow-line Seyfert 1 galaxies in the BeppoSAX Core Program. We also present and discuss a high quality optical spectrum taken at the 1.5 m telescope at La Silla two months before the BeppoSAX observation.

The X-ray spectrum shows a clear hardening above about 2 keV, where a power law with [FORMULA] plus an iron line provide a good description of the data. This slope is significantly steeper than the typical one for classical Seyfert 1's and quasars. The best fit line energy is suggestive of highly ionized iron, which would support the idea that the high accretion rate is (one of) the fundamental parameter(s) characterizing the Narrow Line Seyfert 1 phenomenon.

Key words: X-rays: galaxies – galaxies: Seyfert – galaxies: individual: Ton S 180

Send offprint requests to: A. Comastri (e-mail: comastri@astbo3.bo.astro.it)

© European Southern Observatory (ESO) 1998

Online publication: April 15, 1998
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