The Gamma-Ray Emitting Radio-Loud Narrow-Line Seyfert 1 Galaxy PKS
  2004-447 I. The X-Ray View
  As part of the TANAMI multiwavelength progam, we discuss new X-ray
observations of the $\gamma$-ray and radio-loud Narrow Line Seyfert galaxy
($\gamma$-NLS1) PKS 2004-447. The active galaxy is a member of a small sample
of radio-loud NLS1s detected in $\gamma$-rays by the Fermi Large Area
Telescope. It is the radio-loudest and only southern-hemisphere source in this
sample. We present results from our X-ray monitoring program comprised of Swift
snapshot observations from 2012 through 2014 and two new X-ray observations
with XMM-Newton in 2012. We analyze the X-ray spectrum and variability of this
peculiar source using supplementary archival data from 2004 and 2011. The
(0.5-10) keV spectrum is well described by a flat power law, which can be
interpreted as non-thermal emission from a relativistic jet. The source
exhibits moderate flux variability on timescales of both months and years.
Correlated brightness variations in the (0.5-2) keV and (2-10) keV bands are
explained by a single variable spectral component, such as the jet. A possible
soft excess seen in the data from 2004 cannot be confirmed by the new \xmm{}
observations in 2012. Any contribution to the total flux in 2004 is less than
$20\%$ of the power-law component. The (0.5-10) keV luminosities of PKS
2004-447 are in the range of (0.5--2.7)$\times10^{44}\,\mathrm{erg\,s}^{-1}$. A
comparison of the X-ray properties among the known $\gamma$-NLS1 galaxies shows
that X-ray spectrum is typically dominated by a flat power law without
intrinsic absorption. These objects are moderately variable in their
brightness, while spectral variability is observed in at least two sources. The
major difference across the X-ray spectra of $\gamma$-NLS1s is the luminosity,
which spans a range of almost two orders of magnitude, from
$10^{44}\,\mathrm{erg\,s}^{-1}$ to $10^{46}\,\mathrm{erg\,s}^{-1}$ in the
(0.5-10) keV band.
