469 research outputs found
X-ray variability analysis of a large series of XMM-Newton + NuSTAR observations of NGC 3227
We present a series of X-ray variability results from a long XMM-Newton +
NuSTAR campaign on the bright, variable AGN NGC 3227. We present an analysis of
the lightcurves, showing that the source displays typically
softer-when-brighter behaviour, although also undergoes significant spectral
hardening during one observation which we interpret as due to an occultation
event by a cloud of absorbing gas. We spectrally decompose the data and show
that the bulk of the variability is continuum-driven and, through rms
variability analysis, strongly enhanced in the soft band. We show that the
source largely conforms to linear rms-flux behaviour and we compute X-ray power
spectra, detecting moderate evidence for a bend in the power spectrum,
consistent with existing scaling relations. Additionally, we compute X-ray
Fourier time lags using both the XMM-Newton and - through maximum-likelihood
methods - NuSTAR data, revealing a strong low-frequency hard lag and evidence
for a soft lag at higher frequencies, which we discuss in terms of
reverberation models.Comment: Accepted for publication in MNRAS; 19 pages, 13 figures, 4 tables;
minor typographical errors corrected and reference list update
Evidence for a Truncated Accretion Disc in the Low Luminosity Seyfert Galaxy, NGC 7213?
We present the broad-band 0.6-150 keV Suzaku and Swift BAT spectra of the low
luminosity Seyfert galaxy, NGC 7213. The time-averaged continuum emission is
well fitted by a single powerlaw of photon index Gamma = 1.75 and from
consideration of the Fermi flux limit we constrain the high energy cutoff to be
350 keV < E < 25 MeV. Line emission from both near-neutral iron K_alpha at 6.39
keV and highly ionised iron, from Fe_(xxv) and Fe_(xxvi), is strongly detected
in the Suzaku spectrum, further confirming the results of previous observations
with Chandra and XMM-Newton. We find the centroid energies for the Fe_(xxv) and
Fe_(xxvi) emission to be 6.60 keV and 6.95 keV respectively, with the latter
appearing to be resolved in the Suzaku spectrum. We show that the Fe_(xxv) and
Fe_(xxvi) emission can result from a highly photo-ionised plasma of column
density N_(H) ~ 3 x 10^(23) cm^(-2). A Compton reflection component, e.g.,
originating from an optically-thick accretion disc or a Compton-thick torus,
appears either very weak or absent in this AGN, subtending < 1 sr to the X-ray
source, consistent with previous findings. Indeed the absence of either neutral
or ionised Compton reflection coupled with the lack of any relativistic Fe K
signatures in the spectrum suggests that an inner, optically-thick accretion
disc is absent in this source. Instead, the accretion disc could be truncated
with the inner regions perhaps replaced by a Compton-thin Radiatively
Inefficient Accretion Flow. Thus, the Fe_(xxv) and Fe_(xxvi) emission could
both originate in ionised material perhaps at the transition region between the
hot, inner flow and the cold, truncated accretion disc on the order of 10^(3) -
10^(4) gravitational radii from the black hole. The origin for the unresolved
neutral Fe K_alpha emission is then likely to be further out, perhaps
originating in the optical BLR or a Compton-thin pc-scale torus.Comment: 15 pages, 11 figures, accepted for publication by MNRA
Significant X-ray Line Emission in the 5-6 keV band of NGC 4051
A Suzaku X-ray observation of NGC 4051 taken during 2005 Nov reveals line
emission at 5.44 keV in the rest-frame of the galaxy which does not have an
obvious origin in known rest-frame atomic transitions. The improvement to the
fit statistic when this line is accounted for establishes its reality at >99.9%
confidence: we have also verified that the line is detected in the three XIS
units independently. Comparison between the data and Monte Carlo simulations
shows that the probability of the line being a statistical fluctuation is p <
3.3 x 10^-4. Consideration of three independent line detections in Suzaku data
taken at different epochs yields a probability p< 3 x 10^-11 and thus
conclusively demonstrates that it cannot be a statistical fluctuation in the
data. The new line and a strong component of Fe Ka emission from neutral
material are prominent when the source flux is low, during 2005. Spectra from
2008 show evidence for a line consistent with having the same flux and energy
as that observed during 2005, but inconsistent with having a constant
equivalent width against the observed continuum. The stability of the line flux
and energy suggests that it may not arise in transient hotspots, as has been
suggested for similar lines in other sources, but could arise from a special
location in the reprocessor, such as the inner edge of the accretion disk.
Alternatively, the line energy may be explained by spallation of Fe into Cr, as
discussed in a companion paper.Comment: 18 pages, accepted for publication by Ap
High Resolution X-ray Spectroscopy of the Seyfert 1, Mrk 1040. Revealing the Failed Nuclear Wind with Chandra
High resolution X-ray spectroscopy of the warm absorber in the nearby X-ray bright Seyfert 1 galaxy, Mrk 1040 is presented. The observations were carried out in the 2013-2014 timeframe using the Chandra High Energy Transmission Grating with a total exposure of 200 ks. A multitude of absorption lines from Ne, Mg and Si are detected from a wide variety of ionization states. In particular, the detection of inner K-shell absorption lines from Ne, Mg and Si, from charge states ranging from F-like to Li-like ions, suggests the presence of a substantial amount of low ionization absorbing gas, illuminated by a steep soft X-ray continuum. The observations reveal at least 3 warm absorbing components ranging in ionization parameter from and with column densities of cm. The velocity profiles imply that the outflow velocities of the absorbing gas are low and within km s of the systemic velocity of Mrk 1040, which suggests any outflowing gas may have stalled in this AGN on large enough scales. The warm absorber is likely located far from the black hole, within 300 pc of the nucleus and is spatially coincident with emission from an extended Narrow Line Region as seen in the HST images. The iron K band spectrum reveals only narrow emission lines, with Fe K at 6.4 keV consistent with originating from reflection off Compton thick pc-scale reprocessing gas
Observations of Outflowing UV Absorbers in NGC 4051 with the Cosmic Origins Spectrograph
We present new Hubble Space Telescope (HST)/Cosmic Origins Spectrograph
observations of the Narrow-Line Seyfert 1 galaxy NGC 4051. These data were
obtained as part of a coordinated observing program including X-ray
observations with the Chandra/High Energy Transmission Grating (HETG)
Spectrometer and Suzaku. We detected nine kinematic components of UV
absorption, which were previously identified using the HST/Space Telescope
Imaging Spectrograph. None of the absorption components showed evidence for
changes in column density or profile within the \sim 10 yr between the STIS and
COS observations, which we interpret as evidence of 1) saturation, for the
stronger components, or 2) very low densities, i.e., n_H < 1 cm^-3, for the
weaker components. After applying a +200 km s^-1 offset to the HETG spectrum,
we found that the radial velocities of the UV absorbers lay within the O VII
profile. Based on photoionization models, we suggest that, while UV components
2, 5 and 7 produce significant O VII absorption, the bulk of the X-ray
absorption detected in the HETG analysis occurs in more highly ionized gas.
Moreover, the mass loss rate is dominated by high ionization gas which lacks a
significant UV footprint.Comment: 41 pages, 10 Figures; accepted for publication in the Astrophysical
Journa
Importance and Assessment of Quality of Life in Symptomatic Permanent Atrial Fibrillation: Patient Focus Groups from the RATE-AF Trial.
AIMS: To establish the extent and impact of symptoms in patients with atrial fibrillation (AF), the importance of different aspects of quality of life (QoL), and how we should assess wellbeing. METHODS: Focus groups of patients with symptomatic permanent AF in a trial of heart rate control; the RATE-AF trial randomised 160 patients aged ≥60 years with permanent AF and at least NYHA class II dyspnoea to either digoxin or beta-blockers. Patient and public representatives led the focus groups and performed all data acquisition and analysis, using thematic approaches to interpret patient views about QoL and its measurement. RESULTS: Substantial impairment of health-related QoL was noted in 160 trial patients, with impact on all domains apart from mental health. Eight women and 11 men aged 61-87 years participated in the focus groups. Common themes were a lack of information from healthcare professionals about AF, a lack of focus on QoL in consultations, and a sense of frustration, isolation, and reduced confidence. There was marked variability in symptoms in individual patients, with some describing severe impact on activities of daily living, and profound interaction with comorbidities such as arthritis. Day-to-day variation in QoL and difficulty in attributing symptom burden to AF or other comorbidities led to challenges in questionnaire completion. Consensus was reached that collecting both general and AF-specific QoL would be useful in routine practice, along with participation in peer support, which was empowering for the patients. CONCLUSIONS: The impact of comorbidities is poorly appreciated in the context of AF, with considerable variability in QoL that requires both generic and AF-specific assessment. Improvement in QoL should direct the appraisal, and reappraisal, of treatment decisions for patients with permanent AF
Development of an international standard set of outcome measures for patients with atrial fibrillation: a report of the International Consortium for Health Outcomes Measurement (ICHOM) atrial fibrillation working group.
AIMS: As health systems around the world increasingly look to measure and improve the value of care that they provide to patients, being able to measure the outcomes that matter most to patients is vital. To support the shift towards value-based health care in atrial fibrillation (AF), the International Consortium for Health Outcomes Measurement (ICHOM) assembled an international Working Group (WG) of 30 volunteers, including health professionals and patient representatives to develop a standardized minimum set of outcomes for benchmarking care delivery in clinical settings. METHODS AND RESULTS: Using an online-modified Delphi process, outcomes important to patients and health professionals were selected and categorized into (i) long-term consequences of disease outcomes, (ii) complications of treatment outcomes, and (iii) patient-reported outcomes. The WG identified demographic and clinical variables for use as case-mix risk adjusters. These included baseline demographics, comorbidities, cognitive function, date of diagnosis, disease duration, medications prescribed and AF procedures, as well as smoking, body mass index (BMI), alcohol intake, and physical activity. Where appropriate, and for ease of implementation, standardization of outcomes and case-mix variables was achieved using ICD codes. The standard set underwent an open review process in which over 80% of patients surveyed agreed with the outcomes captured by the standard set. CONCLUSION: Implementation of these consensus recommendations could help institutions to monitor, compare and improve the quality and delivery of chronic AF care. Their consistent definition and collection, using ICD codes where applicable, could also broaden the implementation of more patient-centric clinical outcomes research in AF
The Hot and Energetic Universe: Astrophysics of feedback in local AGN
Understanding the astrophysics of feedback in active galactic nuclei (AGN) is
key to understanding the growth and co-evolution of supermassive black holes
and galaxies. AGN-driven winds/outflows are potentially the most effective way
of transporting energy and momentum from the nuclear scales to the host galaxy,
quenching star formation by sweeping away the gas reservoir. Key questions in
this field are: 1) how do accretion disks around black holes launch
winds/outflows, and how much energy do these carry? 2) How are the energy and
metals accelerated in winds/outflows transferred and deposited into the
circumgalactic medium? X-ray observations are a unique way to address these
questions because they probe the phase of the outflows which carries most of
the kinetic energy. We show how a high throughput, high spectral resolution
instrument like the X-ray Integral Field Unit (X-IFU) on Athena+ will allow us
to address these questions by determining the physical parameters (ionization
state, density, temperature, abundances, velocities, geometry, etc.) of the
outflows on a dynamical time-scale, in a broad sample of nearby bright AGN. The
X-IFU will also allow direct spectral imaging of the impact of these winds on
the host galaxy for local AGN, forming a template for understanding AGN at
higher redshifts where wind shocks cannot be resolved.Comment: Supporting paper for the science theme "The Hot and Energetic
Universe" to be implemented by the Athena+ X-ray observatory
(http://www.the-athena-x-ray-observatory.eu). 10 pages, 6 figure
Ice XII in its second regime of metastability
We present neutron powder diffraction results which give unambiguous evidence
for the formation of the recently identified new crystalline ice phase[Lobban
et al.,Nature, 391, 268, (1998)], labeled ice XII, at completely different
conditions. Ice XII is produced here by compressing hexagonal ice I_h at T =
77, 100, 140 and 160 K up to 1.8 GPa. It can be maintained at ambient pressure
in the temperature range 1.5 < T < 135 K. High resolution diffraction is
carried out at T = 1.5 K and ambient pressure on ice XII and accurate
structural properties are obtained from Rietveld refinement. At T = 140 and 160
K additionally ice III/IX is formed. The increasing amount of ice III/IX with
increasing temperature gives an upper limit of T ~ 150 K for the successful
formation of ice XII with the presented procedure.Comment: 3 Pages of RevTeX, 3 tables, 3 figures (submitted to Physical Review
Letters
Search for Narrow Diphoton Resonances and for gamma-gamma+W/Z Signatures in p\bar p Collisions at sqrt(s)=1.8 TeV
We present results of searches for diphoton resonances produced both
inclusively and also in association with a vector boson (W or Z) using 100
pb^{-1} of p\bar p collisions using the CDF detector. We set upper limits on
the product of cross section times branching ratio for both p\bar
p\to\gamma\gamma + X and p\bar p\to\gamma\gamma + W/Z. Comparing the inclusive
production to the expectations from heavy sgoldstinos we derive limits on the
supersymmetry-breaking scale sqrt{F} in the TeV range, depending on the
sgoldstino mass and the choice of other parameters. Also, using a NLO
prediction for the associated production of a Higgs boson with a W or Z boson,
we set an upper limit on the branching ratio for H\to\gamma\gamma. Finally, we
set a lower limit on the mass of a `bosophilic' Higgs boson (e.g. one which
couples only to \gamma, W, and Z$ bosons with standard model couplings) of 82
GeV/c^2 at 95% confidence level.Comment: 30 pages, 11 figure
- …