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Astron. Astrophys. 356, 33-40 (2000)

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The hard X-ray properties of the Seyfert nucleus in NGC 1365

G. Risaliti 1, R. Maiolino 2 and L. Bassani 3

1 Università di Firenze, Dipartimento di Astronomia e Scienza dello Spazio, Largo E. Fermi 5, 50125 Firenze, Italy (risaliti@arcetri.astro.it)
2 Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy (maiolino@arcetri.astro.it)
3 Istituto T.E.S.R.E., CNR, Via Gobetti 101, 40129 Bologna, Italy (bassani@tesre.bo.cnr.it)

Received 6 July 1999 / Accepted 7 December 1999

Abstract

We present BeppoSAX observations of the Seyfert 1.8 galaxy NGC1365 in the 0.1-100 keV range. The source was 6 times brighter than during an ASCA observation 3 years earlier. The 4-10 keV flux is highly variable during the BeppoSAX observation, while the soft (0.1-4 keV) emission is constant within the errors. Both a cold and a warm reflector and a cold absorber are required to explain the observed spectrum. The comparison between ASCA and BeppoSAX spectra strongly suggests that the circumnuclear material has a more complex structure than a simple homogeneous torus, with quite different absorbing gas columns along different lines of sight. A broad iron K[FORMULA] line is also present in the spectrum, with the peak energy significantly redshifted. This can be explained by means of a relativistic disk line model. Alternatively, a warm absorption Fe line system with NH [FORMULA] 1023 cm-2 could account for the observed line profile.

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

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© European Southern Observatory (ESO) 2000

Online publication: March 28, 2000
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