The%20unusual%20X-ray%20spectrum%20of%20MCG-2-58-22

1
The unusual X-ray spectrum of MCG-2-58-22
-as seen by XMM-Newton and BeppoSAX
N.Salvi, A Orr, M.Page, K.Mason, P.Barr, M.
Guainazzi, A. Parmer,
M. Santos-Lleo, R. Staubert
We present preliminary results from combined
XMM-Newton and BeppoSAX spectroscopy of the
luminous Seyfert I galaxy MCG-2-58-22. Previous
high energy observations of this source were not
able to determine whether the underlying X-ray
continuum in the source is intrinsically flat or
whether the spectral hardness is in fact due to
the presence of a reflection component.
Low level X-ray variability is seen during the
long BeppoSAX observation. The light curves from
both instruments, LECS (0.1-2.0 keV) and MECS
(2-10 keV) show variations in X-ray flux. The
largest changes in count rate are 27 ? (MECS) and
42? (LECS) within 7000 sec (Fig 4).
Our new data set shows that the spectrum between
2-100 keV is indeed hard and can be well
represented by a power-law continuum (? 1.6) and
Fe K? line emission (6.6 keV). We find that
reflection contributes very little to the
continuum spectrum of MCG-2-58-22. The upper
limit to the reflection fraction is 16 at 90
confidence. The ionization parameter is low with
? lt 30 ergs cm s-1 (Fig 2)
Fig 4. The light curves and hardness ratio for
the long BeppaSAX exposure. The length of the XMM
Observation is marked in green.
Fig 2. Contour plot illustrating the fit of a
reflection model to the combined XMMSAX data
(0.1-100 keV MOS RGS LECS MECS PDS). The
plot shows the confidence contours for the
reflection fraction, R (Model Incident R
Reflected) and log (?) the ionization parameter
(defined between 0.01-100 keV)
Fig 1. Simultaneous broken powerlaw model fit to
the BeppoSAX (LECS, MECS, PDS) and XMM (RGS, MOS)
data (?0.1-2 1.8, ?2-100 1. 6 , Ebreak 2.3
keV). The residuals show an Fe line at 6.6 keV
and a complex low energy spectrum.


The XMM-Newton EPIC 0.1-2.0 keV and 2-10 keV
light curves do not exhibit significant flux
variations during the 10 ks exposure (Fig 5).
The high resolution and sensitivity of the
XMM-Newton RGS and EPIC-MOS detectors show a
complex low energy spectrum (E lt 2 keV) with line
and/or continuum flux in excess of the underlying
powerlaw. The low energy residuals remain even
with the addition of a black body excess. The
soft X-ray features can be well described by
relativistic O VIII, N VII and C VI lines (Fig
3). The goodness of fit is improved at ? 99?
confidence level when the lines are added to the
powerlaw model.
Fig 5. The light curves and hardness ratio for
the 10 ks XMM-Newton exposure.
Fig 3. Relativistic disk lines in the soft X-ray
spectrum of MCG-2-58-22.. The best fit lines have
equivalent widths of 20 eV (O VIII), 20 eV (N
VII) and 12 eV (C IV). The plot shows the RGS
data (blue) , MOS data (red), Laor line model
(pink) and powerlaw model (green).