530 research outputs found
A study of the X-rayed outflow of APM 08279+5255 through photoionization codes
We present new results from our study of the X-rayed outflow of the z = 3.91
gravitationally lensed broad absorption line (BAL) quasar APM 08279+5255. These
results are based on spectral fits to all the long exposure observations of APM
08279+5255 using a new quasar-outflow model. This model is based on cloudy
simulations of a near-relativistic quasar outflow. The main conclusions from
our multi-epoch spectral re-analysis of Chandra, XMM-Newton and Suzaku
observations of APM 08279+5255 are: 1) In every observation we confirm the
presence of two strong features, one at rest-frame energies between 1-4 keV,
and the other between 7-18 keV. 2) We confirm that the low-energy absorption
(1-4 keV rest-frame) arises from a low-ionization absorber with logNH~23 and
the high-energy absorption (7-18 keV rest-frame) arises from highly ionized
(3>log xi>4; where xi is the ionization parameter) iron in a near-relativistic
outflowing wind. Assuming this interpretation, we find that the velocities on
the outflow could get up to ~0.7c. 3) We confirm a correlation between the
maximum outflow velocity and the photon index and find possible trends between
the maximum outflow velocity and the X-ray luminosity, and between the total
column density and the photon index. We performed calculations of the force
multipliers of material illuminated by absorbed power laws and a
Mathews-Ferland SED. We found that variations of the X-ray and UV parts of the
SEDs and the presence of a moderate absorbing shield will produce important
changes in the strength of the radiative driving force. These results support
the observed trend found between the outflow velocity and X-ray photon index in
APM 08279+5255. If this result is confirmed it will imply that radiation
pressure is an important mechanism in producing quasar outflows.Comment: Paper accepted in the Astrophysical journa
Confirmation of and Variable Energy Injection by a Near-Relativistic Outflow in APM 08279+5255
We present results from multi-epoch spectral analysis of XMM-Newton and
Chandra observations of the broad absorption line (BAL) quasar APM 08279+5255.
Our analysis shows significant X-ray BALs in all epochs with rest-frame
energies lying in the range of ~ 6.7-18 keV. The X-ray BALs and 0.2-10 keV
continuum show significant variability on timescales as short as 3.3 days
(proper time) implying a source size-scale of ~ 10 r_g, where r_g is the
gravitational radius. We find a large gradient in the outflow velocity of the
X-ray absorbers with projected outflow velocities of up to 0.76 c. The maximum
outflow velocity constrains the angle between the wind velocity and our line of
sight to be less than ~ 22 degrees. We identify the following components of the
outflow: (a) Highly ionized X-ray absorbing material (2.9 < logxi < 3.9) and a
column density of log N_H ~ 23 outflowing at velocities of up to 0.76 c. (b)
Low-ionization X-ray absorbing gas with log N_H ~ 22.8. We find that flatter
spectra appear to result in lower outflow velocities. Based on our spectral
analysis of observations of APM 08279+5255 over a period of 1.2 years (proper
time) we estimate the mass-outflow rate and efficiency of the outflow to have
varied between 16(-8,+12) M_solar yr^-1 and 64(-40,+66) M_solar yr^-1 and
0.18(-0.11,+0.15) to 1.7(-1.2+1.9), respectively. Assuming that the outflow
properties of APM 08279+5255 are a common property of most quasars at similar
redshifts, our results then imply that quasar winds are massive and energetic
enough to influence significantly the formation of the host galaxy, provide
significant metal enrichment to the interstellar medium and intergalactic
medium, and are a viable mechanism for feedback at redshifts near the peak in
the number density of galaxy mergers.Comment: 27 pages, includes 12 figures, accepted for publication in Ap
Revealing the Structure of an Accretion Disk Through Energy Dependent X-ray Microlensing
We present results from monitoring observations of the gravitationally lensed
quasar RX J1131-1231 performed with the Chandra X-ray Observatory. The X-ray
observations were planned with relatively long exposures that allowed a search
for energy-dependent microlensing in the soft (0.2-2 keV) and hard (2-10 keV)
light curves of the images of RX J1131-1231. We detect significant microlensing
in the X-ray light-curves of images A and D, and energy-dependent microlensing
of image D. The magnification of the soft band appears to be larger than that
in the hard band by a factor of ~ 1.3 when image D becomes more magnified. This
can be explained by the difference between a compact, softer-spectrum corona
that is producing a more extended, harder spectrum reflection component off the
disk. This is supported by the evolution of the fluorescent iron line in image
D over three consecutive time-averaged phases of the light curve. In the first
period, a Fe line at E = 6.36(-0.16,+0.13) keV is detected (at > 99%
confidence). In the second period, two Fe lines are detected, one at E =
5.47(-0.08,+0.06) keV (detected at > 99% confidence) and another at E =
6.02(-0.07,+0.09) keV (marginally detected at > 90% confidence), and in the
third period, a broadened Fe line at 6.42(-0.15,+0.19) keV is detected (at >
99% confidence). This evolution of the Fe line profile during the microlensing
event is consistent with the line distortion expected when a caustic passes
over the inner disk where the shape of the fluorescent Fe line is distorted by
General Relativistic and Doppler effects.Comment: 20 pages, includes 10 figures, submitted to Ap
Remarkable Spectral Variability of PDS 456
We report on the highest to date signal-to-noise-ratio X-ray spectrum of the
luminous quasar PDS 456, as obtained during two XMM-Newton orbits in September
2007. The present spectrum is considerably different from several previous
X-ray spectra recorded for PDS 456 since 1998. The ultra-high-velocity outflow
seen as recently as February 2007 is not detected in absorption. Conversely, a
significant reflection component is detected. The reflection model suggests the
reflecting medium may be outflowing at a velocity v/c = -0.06 +/- 0.02. The
present spectrum is analyzed in the context of the previous ones in an attempt
to understand all spectra within the framework of a single model. We examine
whether an outflow with variable partial covering of the X-ray source along the
line of sight that also reflects the source from other lines of sight can
explain the dramatic variations in the broad-band spectral curvature of PDS
456. It is established that absorption plays a major role in shaping the
spectrum of other epochs, while the 2007 XMM-Newton spectrum is dominated by
reflection, and the coverage of the source by the putative outflow is small (<
20%).Comment: submitted to Ap
X-ray Monitoring of Gravitational Lenses With Chandra
We present \emph{Chandra} monitoring data for six gravitationally lensed
quasars: QJ 01584325, HE 04351223, HE 11041805, SDSS 0924+0219, SDSS
1004+4112, and Q 2237+0305. We detect X-ray microlensing variability in all six
lenses with high confidence. We detect energy dependent microlensing in HE
04351223, SDSS 1004+4112, SDSS 0924+0219 and Q 2237+0305. We present a
detailed spectral analysis for each lens, and find that simple power-law models
plus Gaussian emission lines give good fits to the spectra. We detect intrinsic
spectral variability in two epochs of Q 2237+0305. We detect differential
absorption between images in four lenses. We also detect the \feka\ emission
line in all six lenses, and the Ni XXVII K line in two images of Q
2237+0305. The rest frame equivalent widths of the \feka\ lines are measured to
be 0.4--1.2 keV, significantly higher than those measured in typical active
galactic nuclei of similar X-ray luminosities. This suggests that the \feka\
emission region is more compact or centrally concentrated than the continuum
emission region.Comment: 55 pages, 22 figure
Does the X-ray outflow quasar PDS 456 have a UV outflow at 0.3c?
The quasar PDS 456 (at redshift ~0.184) has a prototype ultra-fast outflow
(UFO) measured in X-rays. This outflow is highly ionized with relativistic
speeds, large total column densities log N_H(cm^-2) > 23, and large kinetic
energies that could be important for feedback to the host galaxy. A UV spectrum
of PDS 456 obtained with the Hubble Space Telescope in 2000 contains one
well-measured broad absorption line (BAL) at ~1346A (observed) that might be
Ly-alpha at v ~ 0.06c or NV 1240 at v ~ 0.08c. However, we use photoionisation
models and comparisons to other outflow quasars to show that these BAL
identifications are problematic because other lines that should accompany them
are not detected. We argue that the UV BAL is probably CIV 1549 at v ~ 0.30c.
This would be the fastest UV outflow ever reported, but its speed is similar to
the X-ray outflow and its appearance overall is similar to relativistic UV BALs
observed in other quasars. The CIV BAL identification is also supported
indirectly by the tentative detection of another broad CIV line at v ~ 0.19c.
The high speeds suggest that the UV outflow originates with the X-ray UFO
crudely 20 to 30 r_g from the central black hole. We speculate that the CIV BAL
might form in dense clumps embedded in the X-ray UFO, requiring density
enhancements of only >0.4 dex compared clumpy structures already inferred for
the soft X-ray absorber in PDS 456. The CIV BAL might therefore be the first
detection of low-ionisation clumps proposed previously to boost the opacities
in UFOs for radiative driving.Comment: in press with MNRA
The influence of gravitational lensing on the spectra of lensed QSOs
We consider the influence of (milli/micro)lensing on the spectra of lensed
QSOs. We propose a method for the observational detection of microlensing in
the spectra of lensed QSOs and apply it to the spectra of the three lensed QSOs
(PG 1115+080, QSO 1413+117 and QSO 0957+561) observed with Hubble Space
Telescope (HST). We find that the flux ratio between images A1 and A2 of PG
1115+080 is wavelength-dependent and shows differential magnification between
the emission lines and the continuum. We interpret this magnification as
arising from millilensing. We also find that the temporal variations in the
continuum of image C of QSO 1413+117 may be caused by microlensing, while the
temporal variation observed in QSO 0957+561 was probably an intrinsic one.Comment: 11 pages, accepted for publication in MNRA
Probing Broad Absorption Line Quasar Outflows: X-ray Insights
Energetic outflows appear to occur in conjunction with active mass accretion
onto supermassive black holes. These outflows are most readily observed in the
approximately 10% of quasars with broad absorption lines, where the observer's
line of sight passes through the wind. Until fairly recently, the paucity of
X-ray data from these objects was notable, but now sensitive hard-band missions
such as Chandra and XMM-Newton are routinely detecting broad absorption line
quasars. The X-ray regime offers qualitatively new information for the
understanding of these objects, and these new results must be taken into
account in theoretical modeling of quasar winds.Comment: Submitted to Advances in Space Research for New X-ray Results from
Clusters of Galaxies and Black Holes (Oct 2002; Houston, TX), eds. C. Done,
E.M. Puchnarewicz, M.J. Ward. Requires cospar.sty (6 pgs, 5 figs
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