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Astron. Astrophys. 341, L39-L42 (1999)

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Letter to the Editor

One more surprise from the Circinus Galaxy: BeppoSAX discovery of a transmission component in hard X-rays

G. Matt 1, M. Guainazzi 2, R. Maiolino 3, S. Molendi 4, G.C. Perola 1, L.A. Antonelli 5,6, L. Bassani 7, W.N. Brandt 8, A.C. Fabian 9, F. Fiore 5,6, K. Iwasawa 9, G. Malaguti 7, A. Marconi 3 and J. Poutanen 10

1 Dipartimento di Fisica "E. Amaldi", Università degli Studi "Roma Tre", Via della Vasca Navale 84, I-00146 Roma, Italy
2 Astrophysics Division, Space Science Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
3 Osservatorio Astrofisico di Arcetri, L.E. Fermi 5, I-50125 Firenze, Italy
4 Istituto di Fisica Cosmica e Tecnologie Relative, Via Bassini 15, I-20133 Milano, Italy
5 Osservatorio Astronomico di Roma, Via dell'Osservatorio, I-00044 Monteporzio-Catone, Italy
6 SAX/SDC Nuova Telespazio, Via Corcolle 19, I-00131 Roma, Italy
7 Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Via Gobetti 101, I-40129 Bologna, Italy
8 Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA
9 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK
10 Stockholm Observatory, SE-133 36 Saltsjöbaden, Sweden

Received 27 October 1998 / Accepted 19 November 1998


The Circinus Galaxy has been observed, for the first time above 10 keV, by BeppoSAX. An excess emission above the extrapolation of the best fit 0.1-10 keV spectrum is apparent in the PDS data. The most likely explanation is that we are observing the nucleus through a column density of [FORMULA] cm-2, i.e. large enough to completely block the radiation below 10 keV but small enough to permit partial transmission above this energy.

Key words: X-rays: galaxies – galaxies: Seyfert – galaxies: individual: Circinus

SIMBAD Objects


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© European Southern Observatory (ESO) 1999

Online publication: December 4, 1998