579 research outputs found
XMM-Newton discovery of soft X-ray absorption in the high-z superluminous Blazar RBS 315
We present the analysis and the results of a 20 ks XMM-Newton observation of
the extremely X-ray loud (L_X ~ 5 x 10^{47} erg/s) flat-spectrum radio quasar
RBS 315 at a redshift of 2.69. This EPIC observation has allowed us to strongly
constrain the slope of the continuum (Gamma = 1.23+/-0.01) as well as to
discover the presence of a sharp drop below ~ 2 keV in its spectrum. Such a
flat photon index and the huge luminosity suggest that the X-ray emission is
due to the low energy tail of the Comptonized spectrum, produced from plasma in
a relativistic jet oriented close to our line of sight. Even though the
hypothesis of a break in the continuum cannot be completely discarded as an
explanation of the soft X-ray cutoff, the presence of intrinsic absorption
appears more plausible. Spectral fits with cold (Nh(z) = 1.62+/-0.09 x 10^{22}
cm^{-2}) and lukewarm (Nh(z) = 2.2^{+0.9}_{-0.3} x 10^{22} cm^{-2}; xi =
15^{+38}_{-12} erg/cm^{2}/s) absorbers are statistically indistinguishable.
Remarkably, our results are very similar to those reported so far for other
absorbed high-z Blazars observed by XMM-Newton. The existence of this
``homogeneous'' class of jet-dominated superluminous obscured QSOs at high z
therefore could be important in the context of the formation and cosmological
evolution of radio-loud objectsComment: Accepted by A&A Letter
An X-ray variable absorber within the Broad Line Region in Fairall 51
Fairall 51 is a polar-scattered Seyfert 1 galaxy, a type of active galaxies
believed to represent a bridge between unobscured type-1 and obscured type-2
objects. Fairall 51 has shown complex and variable X-ray absorption but only
little is known about its origin. In our research, we observed Fairall 51 with
the X-ray satellite Suzaku in order to constrain a characteristic time-scale of
its variability. We performed timing and spectral analysis of four observations
separated by 1.5, 2 and 5.5 day intervals. We found that the 0.5-50 keV
broadband X-ray spectra are dominated by a primary power-law emission (with the
photon index ~ 2). This emission is affected by at least three absorbers with
different ionisations (log(xi) ~ 1-4). The spectrum is further shaped by a
reprocessed emission, possibly coming from two regions -- the accretion disc
and a more distant scattering region. The accretion disc emission is smeared by
the relativistic effects, from which we measured the spin of the black hole as
a ~ 0.8 (+-0.2). We found that most of the spectral variability can be
attributed to the least ionised absorber whose column density changed by a
factor of two between the first (highest-flux) and the last (lowest-flux)
observation. A week-long scale of the variability indicates that the absorber
is located at the distance ~ 0.05 pc from the centre, i.e., in the Broad Line
Region.Comment: 12 pages, 9 figures, accepted to A&
Active galaxy 4U 1344-60: did the relativistic line disappear?
X-ray bright active galactic nuclei represent a unique astrophysical
laboratory for studying accretion physics around super-massive black holes. 4U
1344-60 is a bright Seyfert galaxy which revealed relativistic reflection
features in the archival XMM-Newton observation. We present the spectroscopic
results of new data obtained with the Suzaku satellite and compare them with
the previous XMM-Newton observation. The X-ray continuum of 4U 1344-60 can be
well described by a power-law component with the photon index ~ 1.7 modified by
a fully and a partially covering local absorbers. We measured a substantial
decrease of the fraction of the partially absorbed radiation from around 45% in
the XMM-Newton observation to less than 10% in the Suzaku observation while the
power-law slope remains constant within uncertainties. The iron line in the
Suzaku spectrum is relatively narrow, keV, without any
suggestion for relativistic broadening. Regarding this, we interpret the iron
line in the archival XMM-Newton spectrum as a narrow line of the same width
plus an additional red-shifted emission around 6.1 keV. No evidence of the
relativistic reflection is present in the Suzaku spectra. The detected
red-shifted iron line during the XMM-Newton observation could be a temporary
feature either due to locally enhanced emission or decreased ionisation in the
innermost accretion flow.Comment: 10 pages, 11 figures, accepted to A&
Chandra imaging of the kpc extended outflow in 1H 0419-577
The Seyfert 1 galaxy 1H 0419-577 hosts a kpc extended outflow that is
evident in the [\ion{O}{iii}] image and that is also detected as a warm
absorber in the UV/X-ray spectrum. Here, we analyze a 30 ks Chandra-ACIS
X-ray image, with the aim of resolving the diffuse extranuclear X-ray emission
and of investigating its relationship with the galactic outflow. Thanks to its
sub-arcsecond spatial resolution, Chandra resolves the circumnuclear X-ray
emission, which extends up to a projected distance of at least 16 kpc
from the center. The morphology of the diffuse X-ray emission is spherically
symmetrical. We could not recover a morphological resemblance between the soft
X-ray emission and the ionization bicone that is traced by the [\ion{O}{iii}]
outflow. we argue that the photoionized gas nebula must be distributed mostly
along the polar directions, outside our line of sight. In this geometry, the
X-ray/UV warm absorber must trace a different gas component, physically
disconnected from the emitting gas, and located closer to the equatorial plane.Comment: accepted for publications A&
XMM-Newton view of the double-peaked Fe K-alpha complex in E1821+643
We present the results of the analysis of the hard band XMM-Newton spectra of
the luminous, L(2-10keV)~3.4E+45 erg/s, radio-quiet quasar, E1821+643. Two
emission features were observed in the 6-7 keV rest frame band, confirming
previous Chandra detection of these structures. We interpret these features as
two single emission lines, one consistent with the neutral Fe K-alpha line at
6.4 keV and the other most likely due to FeXXVI. If related to the quasar, the
high-energy emission line should originate in highly ionised matter, i.e. the
accretion disc or the clouds of the emission line regions. Alternatively, it
may be related to the intergalactic medium of the rich galaxy cluster in which
E1821+643 is embedded. A composite broad emission line in combination with an
absorption line model, however, also fits the data well. We discuss the
possible physical interpretations of the origin of these features.Comment: Accepted for publication in A&A, 7 pages and 7 figure
The XMM-Newton view of IRAS 09104+4109: evidence for a changing-look Type 2 quasar?
We analyzed the spectroscopic data from the PN and the MOS cameras in the
0.4-10 keV band. We also used an archival BeppoSAX 1-50 keV observation of IRAS
09104+4109 to investigate possible variations of the quasar emission. The X-ray
emission in the EPIC band is dominated by the intra-cluster medium thermal
emission. We found that the quasar contributes ~35% of the total flux in the
2-10 keV band. Both a transmission- (through a Compton-thin absorber with a
Compton optical depth of \tau_C~0.3, i.e. Nh~5 x 10^{23} cm^-2) and a
reflection-dominated (\tau_C>1) model provide an excellent fit to the quasar
continuum emission. However, the value measured for the EW of Fe Kalpha
emission line is only marginally consistent with the presence of a
Compton-thick absorber in a reflection-dominated scenario, which had been
suggested by a previous, marginal (i.e. 2.5\sigma) detection with the hard
X-ray (15-50 keV), non-imaging BeppoSAX/PDS instrument. Moreover, the value of
luminosity in the 2-10 keV band measured by the transmission-dominated model is
fully consistent with that expected on the basis of the bolometric luminosity
of IRAS 09104+4109. From the analysis of the XMM-Newton data we therefore
suggest the possibility that the absorber along the line of sight to the
nucleus of IRAS 09104+4109 is Compton-thin. Alternatively, the absorber column
density could have changed from Compton-thick to -thin in the five years
elapsed between the observations. If this is the case, then IRAS 09104+4109 is
the first 'changing-look' quasar ever detected.Comment: Accepted by Astronomy and Astrophysic
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