Simultaneous XMM-Newton and BeppoSAX observation of the Seyfert I galaxy IC 4329A

Free access article

Issue		A&A Volume 378, Number 3, November II 2001


Page(s)		806 - 816
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20011258

A&A 378, 806-816 (2001)
DOI: 10.1051/0004-6361:20011258

Simultaneous XMM-Newton and BeppoSAX observation of the Seyfert I galaxy IC 4329A

P. Gondoin, P. Barr, D. Lumb, T. Oosterbroek, A. Orr and A. N. Parmar

Astrophysics Division, European Space Agency -Postbus 299, 2200 AG Noordwijk, The Netherlands

(Received 1 June 2001 / Accepted 6 September 2001)

Abstract
We report on a simultaneous XMM-Newton and BeppoSAX observation of the Seyfert 1 galaxy IC 4329A performed in 2001 January. Above 1 keV, EPIC spectra show a narrow Fe K emission line at 6.42 ^+0.04_-0.03 keV with an equivalent width of $43\pm1$ eV. An absorption edge is detected at $7.1\pm0.4$ keV in the source rest frame that has not been reported before. The energy of these features is consistent with reflection of the primary X-ray continuum by a optically thick material containing iron in low states of ionization. The narrow Fe K feature suggests that the reflection arises relatively far from a putative central black hole. Spectral fitting of simultaneous XMM-Newton and BeppoSAX data over the 0.3-130 keV energy range shows that the primary continuum is well described by a cut-off power law with a photon index of $1.93\pm0.03$ and a folding energy of $260\pm130$ keV. The high energy tail >10 keV constrains the reflection fraction close to unity. Fitting over the overall spectral range indicates that the Fe abundance within the cool reflecting material is not significantly different from the cosmic value. The extrapolation of the primary power law continuum to energies <1 keV indicates the presence of absorption edges produced by neutral and ionized oxygen. The optical depth of the O ${\rm I}$ edge at 0.54 keV constrains the intrinsic absorption by neutral material to an hydrogen column density of $=(33 \pm 3)\times10^{20}$ cm^-2 along the line of sight to IC 4329A nucleus. The energy of the edge at $0.854\pm0.009$ keV is consistent with absorption by O ${\rm VIII}$ . A third edge at $0.660\pm0.008$ keV is likely related to absorption by O ${\rm VI}$ and N ${\rm VII}$ . The simultaneous presence of O ${\rm VI}$ and O ${\rm VIII}$ edges without significant O ${\rm VII}$ absorption indicates that the warm absorber originates from at least two zones.

Key words: galaxies: individual: IC 4329A -- galaxies: nuclei -- galaxies: Seyfert

Offprint request: P. Gondoin, pgondoin@astro.estec.esa.nl

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