Issue |
A&A
Volume 466, Number 3, May II 2007
|
|
---|---|---|
Page(s) | 855 - 863 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20066439 | |
Published online | 24 April 2007 |
XMM-Newton broad-band observations of NGC 7582: N
variations and fading out of the active nucleus
1
Osservatorio Astronomico di Roma (INAF), via Frascati 33, 00040 Monteporzio Catone, Italy e-mail: piconcelli@oa-roma.inaf.it
2
European Space Astronomy Center of ESA, Apartado 50727, 28080 Madrid, Spain
3
Dipartimento di Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy
4
Space Telescope Science Institute, 3700 San Martin Drive, MD 21218, USA
Received:
25
September
2006
Accepted:
7
February
2007
We present results from two XMM–Newton observations of the bright
classical Seyfert 2 galaxy NGC 7582 taken four years apart (2001 May and 2005
April). We present the analysis of the
high-resolution (0.3-1 keV) RGS and low-resolution (0.3-10 keV)
EPIC spectroscopic data.
A comparison with a 1998 BeppoSAX observation suggests that XMM–Newton caught the
source in a “reflection-dominated” phase, measuring the lowest continuum
flux level ever (F2-10 = 2.3 10-12 erg cm-2 s-1) in 2005. NGC 7582 therefore
experienced a dramatic spectral transition most likely due to the partial
switching-off of the nuclear activity. The XMM–Newton spectrum of the continuum
emission is very complex. It can be well described by a model consisting of
a combination of a heavily absorbed (NH ~ 1024 cm-2) power law and
a pure reflection component both obscured by a column density of ~
cm-2. Notably, we detect a significant increase by a
factor of ~2 in the column density of the inner, thicker absorber covering
the primary X-ray source between 2001 and 2005. The 2005 XMM–Newton spectrum shows the
strongest Fe Kα emission line
ever measured in this source. This is consistent with the line delayed
time response to the decrease of the nuclear activity.
Our analysis also reveals that the soft
X-ray spectrum is dominated by emission lines from highly ionized
metals. The detection of a narrow OVIII radiative recombination continuum
suggests an origin in a photoionized plasma.
Key words: galaxies: individual: NGC 7582 / galaxies: active / Galaxy: nucleus / X-ray: galaxies
© ESO, 2007
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