459 research outputs found
Constraining the Spin of the Black Hole in Fairall 9 with Suzaku
We report on the results of spectral fits made to data obtained from a 168
ksec Suzaku observation of the Seyfert-1 galaxy Fairall 9. The source is
clearly detected out to 30 keV. The observed spectrum is fairly simple; it is
well-described by a power-law with a soft excess and disk reflection. A broad
iron line is detected, and easily separated from distinct narrow components
owing to the resolution of the CCDs in the X-ray Imaging Spectrometer (XIS).
The broad line is revealed to be asymmetric, consistent with a disk origin. We
fit the XIS and Hard X-ray Detector (HXD) spectra with relativistically-blurred
disk reflection models. With the assumption that the inner disk extends to the
innermost stable circular orbit, the best-fit model implies a black hole spin
parameter of a = 0.60(7) and excludes extremal values at a high level of
confidence. We discuss this result in the context of Seyfert observations and
models of the cosmic distribution of black hole spin.Comment: Accepted for publication in Ap
The changing X-ray time lag in MCG-6-30-15
MCG-6-30-15 is one of the most observed Narrow Line Seyfert 1 galaxies in the
X-ray band. In this paper we examine the X-ray time lags in this source using a
total of 600 ks in observations (440 ks exposure) taken with the XMM-Newton
telescope (300 ks in 2001 and 300 ks in 2013). Both the old and new
observations show the usual hard lag that increases with energy, however, the
hard lag turns over to a soft lag at frequencies below ~1e-4 Hz. The highest
frequencies (~1e-3 Hz) in this source show a clear soft lag, as previously
presented for the first 300 ks observation, but no clear iron K lag is detected
in either the old or new observation. The soft lag is more significant in the
old observation than the new. The observations are consistent with a
reverberation interpretation, where the soft, reflected emission is delayed
with respect to the hard powerlaw component. These spectral timing results
suggest that two distinct variability mechanisms are important in this source:
intrinsic coronal variations (which lead to correlated variability in the
reprocessed emission), and geometrical changes in the corona. Variability due
to geometrical changes does not result in correlated variability in the
reflection, and therefore inhibits the clear detection of an iron K lag.Comment: Resubmitted to MNRAS after minor corrections. 11 pages, 10 figure
A Suzaku, NuSTAR, and XMM-Newton view on variable absorption and relativistic reflection in NGC 4151
We disentangle X-ray disk reflection from complex line-of-sight absorption in
the nearby Seyfert NGC 4151, using a suite of Suzaku, NuSTAR, and XMM-Newton
observations. Extending upon earlier published work, we pursue a physically
motivated model using the latest angle-resolved version of the lamp-post
geometry reflection model relxillCp_lp together with a Comptonization
continuum. We use the long-look simultaneous Suzaku/NuSTAR observation to
develop a baseline model wherein we model reflected emission as a combination
of lamp-post components at the heights of 1.2 and 15.0 gravitational radii. We
argue for a vertically extended corona as opposed to two compact and distinct
primary sources. We find two neutral absorbers (one full-covering and one
partial-covering), an ionized absorber (), and a highly-ionized
ultra-fast outflow, which have all been reported previously. All analyzed
spectra are well described by this baseline model. The bulk of the spectral
variability between 1 keV and 6 keV can be accounted for by changes in the
column density of both neutral absorbers, which appear to be degenerate and
inversely correlated with the variable hard continuum component flux. We track
variability in absorption on both short (2 d) and long (1 yr) timescales;
the observed evolution is either consistent with changes in the absorber
structure (clumpy absorber at distances ranging from the broad line region
(BLR) to the inner torus or a dusty radiatively driven wind) or a geometrically
stable neutral absorber that becomes increasingly ionized at a rising flux
level. The soft X-rays below 1 keV are dominated by photoionized emission from
extended gas that may act as a warm mirror for the nuclear radiation.Comment: 21 pages, 19 figures, 8 tables, accepted for publication by A&
Revealing the X-ray Variability of AGN with Principal Component Analysis
We analyse a sample of 26 active galactic nuclei with deep XMM-Newton
observations, using principal component analysis (PCA) to find model
independent spectra of the different variable components. In total, we identify
at least 12 qualitatively different patterns of spectral variability, involving
several different mechanisms, including five sources which show evidence of
variable relativistic reflection (MCG-6-30-15, NGC 4051, 1H 0707-495, NGC 3516
and Mrk 766) and three which show evidence of varying partial covering neutral
absorption (NGC 4395, NGC 1365, and NGC 4151). In over half of the sources
studied, the variability is dominated by changes in a power law continuum, both
in terms of changes in flux and power law index, which could be produced by
propagating fluctuations within the corona. Simulations are used to find unique
predictions for different physical models, and we then attempt to qualitatively
match the results from the simulations to the behaviour observed in the real
data. We are able to explain a large proportion of the variability in these
sources using simple models of spectral variability, but more complex models
may be needed for the remainder. We have begun the process of building up a
library of different principal components, so that spectral variability in AGN
can quickly be matched to physical processes. We show that PCA can be an
extremely powerful tool for distinguishing different patterns of variability in
AGN, and that it can be used effectively on the large amounts of high-quality
archival data available from the current generation of X-ray telescopes.Comment: 25 pages, 27 figures, accepted to MNRAS. Analysis code available on
request to lead author. Edit: Rogue table remove
NuSTAR Reveals the Comptonizing Corona of the Broad-Line Radio Galaxy 3C 382
Broad-line radio galaxies (BLRGs) are active galactic nuclei that produce
powerful, large-scale radio jets, but appear as Seyfert 1 galaxies in their
optical spectra. In the X-ray band, BLRGs also appear like Seyfert galaxies,
but with flatter spectra and weaker reflection features. One explanation for
these properties is that the X-ray continuum is diluted by emission from the
jet. Here, we present two NuSTAR observations of the BLRG 3C 382 that show
clear evidence that the continuum of this source is dominated by thermal
Comptonization, as in Seyfert 1 galaxies. The two observations were separated
by over a year and found 3C 382 in different states separated by a factor of
1.7 in flux. The lower flux spectrum has a photon-index of
, while the photon-index of the higher flux
spectrum is . Thermal and anisotropic
Comptonization models provide an excellent fit to both spectra and show that
the coronal plasma cooled from keV in the low flux data to
keV in the high flux observation. This cooling behavior is
typical of Comptonizing corona in Seyfert galaxies and is distinct from the
variations observed in jet-dominated sources. In the high flux observation,
simultaneous Swift data are leveraged to obtain a broadband spectral energy
distribution and indicates that the corona intercepts % of the optical
and ultraviolet emitting accretion disk. 3C 382 exhibits very weak reflection
features, with no detectable relativistic Fe K line, that may be best
explained by an outflowing corona combined with an ionized inner accretion
disk.Comment: 8 pages, 8 figures, accepted by Ap
A Hard Look at NGC 5347: Revealing a Nearby Compton-thick AGN
Current measurements show that the observed fraction of Compton-thick (CT) active galactic nuclei (AGN) is smaller than the expected values needed to explain the cosmic X-ray background. Prior fits to the X-ray spectrum of the nearby Seyfert-2 galaxy NGC 5347 (z = 0.00792, D = 35.5 Mpc ) have alternately suggested a CT and Compton-thin source. Combining archival data from Suzaku, Chandra, and—most importantly—new data from NuSTAR, ... See full text for complete abstrac
NuSTAR and Suzaku X-ray Spectroscopy of NGC 4151: Evidence for Reflection from the Inner Accretion Disk
We present X-ray timing and spectral analyses of simultaneous 150 ks Nuclear
Spectroscopic Telescope Array (NuSTAR) and Suzaku X-ray observations of the
Seyfert 1.5 galaxy NGC 4151. We disentangle the continuum emission, absorption,
and reflection properties of the active galactic nucleus (AGN) by applying
inner accretion disk reflection and absorption-dominated models. With a
time-averaged spectral analysis, we find strong evidence for relativistic
reflection from the inner accretion disk. We find that relativistic emission
arises from a highly ionized inner accretion disk with a steep emissivity
profile, which suggests an intense, compact illuminating source. We find a
preliminary, near-maximal black hole spin a>0.9 accounting for statistical and
systematic modeling errors. We find a relatively moderate reflection fraction
with respect to predictions for the lamp post geometry, in which the
illuminating corona is modeled as a point source. Through a time-resolved
spectral analysis, we find that modest coronal and inner disk reflection flux
variation drives the spectral variability during the observations. We discuss
various physical scenarios for the inner disk reflection model, and we find
that a compact corona is consistent with the observed features.Comment: 20 pages, 12 figures, accepted for publication in Ap
The broad band spectral variability of MCG-6-30-15 observed by NuSTAR and XMM-Newton
MCG-6-30-15, at a distance of 37 Mpc (z=0.008), is the archetypical Seyfert 1
galaxy showing very broad Fe K emission. We present results from a
joint NuSTAR and XMM-Newton observational campaign that, for the first time,
allows a sensitive, time-resolved spectral analysis from 0.35 keV up to 80 keV.
The strong variability of the source is best explained in terms of intrinsic
X-ray flux variations and in the context of the light bending model: the
primary, variable emission is reprocessed by the accretion disk, which produces
secondary, less variable, reflected emission. The broad Fe K profile
is, as usual for this source, well explained by relativistic effects occurring
in the innermost regions of the accretion disk around a rapidly rotating black
hole. We also discuss the alternative model in which the broadening of the Fe
K is due to the complex nature of the circumnuclear absorbing
structure. Even if this model cannot be ruled out, it is disfavored on
statistical grounds. We also detected an occultation event likely caused by BLR
clouds crossing the line of sight.Comment: 19 pages, 16 figures, accepted for publication on Ap
Self-consistent Black Hole Accretion Spectral Models and the Forgotten Role of Coronal Comptonization of Reflection Emission
Continuum and reflection spectral models have each been widely employed in measuring the spins of accreting black holes. However, the two approaches have not been implemented together in a photon-conserving, self-consistent framework. We develop such a framework using the black hole X-ray binary GX 339–4 as a touchstone source, and we demonstrate three important ramifications. (1) Compton scattering of reflection emission in the corona is routinely ignored, but is an essential consideration given that reflection is linked to the regimes with strongest Comptonization. Properly accounting for this causes the inferred reflection fraction to increase substantially, especially for the hard state. Another important impact of the Comptonization of reflection emission by the corona is the downscattered tail. Downscattering has the potential to mimic the relativistically broadened red wing of the Fe line associated with a spinning black hole. (2) Recent evidence for a reflection component with a harder spectral index than the power-law continuum is naturally explained as Compton-scattered reflection emission. (3) Photon conservation provides an important constraint on the hard state's accretion rate. For bright hard states, we show that disk truncation to large scales R ≫ R[subscript ISCO] is unlikely as this would require accretion rates far in excess of the observed [dotM] of the brightest soft states. Our principal conclusion is that when modeling relativistically broadened reflection, spectral models should allow for coronal Compton scattering of the reflection features, and when possible, take advantage of the additional constraining power from linking to the thermal disk component.United States. National Aeronautics and Space Administration (PF5-160144
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