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Astron. Astrophys. 344, 857-867 (1999)


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BeppoSAX observations of Mkn 3: Piercing through the torus of a Seyfert 2 galaxy

M. Cappi 1, L. Bassani 1, A. Comastri 2, M. Guainazzi 3, T. Maccacaro 4, G. Malaguti 1, G. Matt 5, G.G.C. Palumbo 6,1, P. Blanco 7, M. Dadina 8, D. DalFiume 1, G. DiCocco 1, A.C. Fabian 9, F. Frontera 1, R. Maiolino 10, L. Piro 11, M. Trifoglio 1 and N. Zhang 12

1 Istituto TeSRE-CNR, Via Gobetti 101, I-40129 Bologna, Italy
2 Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna, Italy
3 Astrophysics Division, SCD -ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
4 Osservatorio Astronomico di Brera, Via Brera 28, I-20121 Milano, Italy
5 Dipartimento di Fisica, Universita' di RomaIII, Via della Vasca Navale 84, I-00146 Roma, Italy
6 Dipartimento di Astronomia, Universita` di Bologna, Via Ranzani 1, I-40127 Bologna, Italy
7 UCSD, San Diego-Ca, USA
8 BeppoSAX S.D.C., ASI, Via Corcolle 19, I-00131 Rome, Italy
9 Institute of Astronomy, Cambridge University, Madingley Road, Cambridge CB3 0HA, UK
10 Osservatorio Astrofisico di Arcetri, Via L.E. Fermi 5, I-5015 Firenze, Italy
11 Istituto di Astrofisica Spaziale, Via Del Fosso del Cavaliere, I-001333 Roma, Italy
12 University Space Research Association, Huntsville-Al, USA

Received 19 October 1998 / Accepted 5 January 1999

Abstract

A new BeppoSAX broad-band (0.6-150 keV) spectrum of the Seyfert 2 galaxy Mkn 3 is presented. The spectrum provides a direct measurement of a large, neutral column of gas with [FORMULA] [FORMULA] 1024 cm-2 in the source direction. The source, as bright as 3C 273 above 10 keV, has a steep ([FORMULA] [FORMULA] 1.8) spectrum without any evidence of a high-energy cutoff up to at least 150 keV. At lower energies, the data are best modeled with the addition of an unabsorbed reflection component. Combining these data with previous Ginga and ASCA observations, the Fe [FORMULA] and reflection continuum indicate that the reprocessed emission is responding slower than the intrinsic continuum variations suggesting a size of the reprocessor [FORMULA] 2 pc. Identifying such a reprocessor with a (close to edge-on) obscuring torus, the overall result fits well into unified models since, presumably, one can interpret the strong absorption as due to transmission through the rim of the torus and the unabsorbed (directly viewed) reflection component as due to reprocessing from the torus inner surface.

Key words: galaxies: individual: Mkn 3 – galaxies: Seyfert – X-rays: galaxies

Send offprint requests to: M. Cappi (mcappi@tesre.bo.cnr.it)

© European Southern Observatory (ESO) 1999

Online publication: March 29, 1999

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