501 research outputs found
On why the Iron K-shell absorption in AGN is not a signature of the local Warm/Hot Intergalactic Medium
We present a comparison between the 2001 XMM-Newton and 2005 Suzaku
observations of the quasar, PG1211+143 at z=0.0809. Variability is observed in
the 7 keV iron K-shell absorption line (at 7.6 keV in the quasar frame), which
is significantly weaker in 2005 than during the 2001 XMM-Newton observation.
From a recombination timescale of <4 years, this implies an absorber density
n>0.004 particles/cm3, while the absorber column is 5e22<N_H <1 1e24
particles/cm2. Thus the sizescale of the absorber is too compact (pc scale) and
the surface brightness of the dense gas too high (by 9-10 orders of magnitude)
to arise from local hot gas, such as the local bubble, group or Warm/Hot
Intergalactic Medium (WHIM), as suggested by McKernan et al. (2004, 2005).
Instead the iron K-shell absorption must be associated with an AGN outflow with
mildly relativistic velocities. Finally we show that the the association of the
absorption in PG1211+143 with local hot gas is simply a coincidence, the
comparison between the recession and iron K absorber outflow velocities in
other AGN does not reveal a one to one kinematic correlation.Comment: accepted for publication in MNRAS LETTERS. 5 pages, 4 figure
Probing the face-on disc-corona system of the bare AGN Mrk 110 from UV to hard X-rays: a moderate changing-state AGN?
[Abridged] The X-ray broadband spectra of the bare AGN Mrk 110, obtained by
simultaneous XMM-Newton and NuSTAR observations (Nov 2019 and April 2020), are
characterised by the presence of a prominent and absorption-free smooth soft
X-ray excess, moderately broad OVII and Fe Kalpha emission lines, and a lack of
a strong Compton hump. While relativistic reflection as the sole emission is
ruled out, a simplified combination of soft and hard Comptonisation from a warm
and a hot coronae, plus mild relativistic disc reflection reproduces the data
very well. We aim to confirm the physical origin of the soft X-ray excess of
Mrk 110 and to determine its disc-corona system properties from its energetics
using two new sophisticated models: reXcor and relagn, respectively. At both
epochs, the inferred high-values of the warm-corona heating from the X-ray
broadband spectral analysis using reXcor confirm that the soft X-ray excess
originates mainly from a warm corona rather than relativistic reflection. The
intrinsic best-fit SED determined at both epochs using relagn show a high X-ray
contribution relative to the UV and are very well reproduced by a warm and hot
coronae plus mild relativistic reflection. The outer radii of the hot and warm
coronae are located at a few 10s and ~100 Rg, respectively. Moreover, combining
the inferred low Eddington ratio (~ a few %) from this work, and previous
multi-wavelength spectral and timing studies suggests that Mrk 110 could be
classified as a moderate changing-state AGN. Our analysis confirms the
existence of a warm corona as a significant contribution to the soft X-ray
excess and UV emission in Mrk 110, adding to growing evidence that AGN
accretion deviates from standard disc theory. This strengthens the importance
of long-term multi-wavelength monitoring on both single targets and large AGN
surveys to reveal the real nature of disc-corona system in AGN.Comment: 12 pages, 7 figures, accepted for publication in A&
Suzaku wide-band X-ray Spectroscopy of the Seyfert 2 AGN in NGC 4945
Suzaku observed a nearby Seyfert 2 galaxy NGC4945, which hosts one of the
brightest active galactic nuclei above 20 keV. Combining data from the X-ray
CCD camera (XIS) and the Hard X-ray Detector (HXD), the AGN intrinsic nuclear
emission and its reprocessed signals were observed simultaneously. The
intrinsic emission is highly obscured with an absorbing column of cm, and was detectable only above keV. The
spectrum below 10 keV is dominated by reflection continuum and emission lines
from neutral/ionized material. Along with a neutral iron K line, a
neutral iron K and a neutral nickel K line were detected for the
first time from this source. The neutral lines and the cold reflection
continuum are consistent with both originating in the same location. The
Compton down-scattered shoulder in the neutral Fe-K line is
in flux of the narrow core, which confirms that the line originates from
reflection rather than transmission. The weakness of the Compton shoulder also
indicates that the reflector is probably seen nearly edge-on. Flux of the
intrinsic emission varied by a factor of within ks, which
requires the obscuring material to be geometrically thin. Broadband spectral
modeling showed that the solid angle of the neutral reflector is less than a
few . All this evidence regarding the reprocessed
signals suggests that a disk-like absorber/reflector is viewed from a near
edge-on angle.Comment: 11 pages, 11 figure
Simulating North American Weather Types With Regional Climate Models
Regional climate models (RCMs) are able to simulate small-scale processes that are missing in their coarser resolution driving data and thereby provide valuable climate information for climate impact assessments. Less attention has been paid to the ability of RCMs to capture large-scale weather types (WTs). An inaccurate representation of WTs can result in biases and uncertainties in current and future climate simulations that cannot be easily detected by standard model evaluation metrics. Here we define 12 hydrologically important WTs in the contiguous United States (CONUS). We test if RCMs from the North American CORDEX (NA-CORDEX) and the Weather Research and Forecasting (WRF) model large physics ensembles (WRF36) can capture those WTs in the current climate and how they simulate changes in the future. Our results show that the NA-CORDEX RCMs are able to simulate WTs more accurately than members of the WRF36 ensemble. The much larger WRF36 domain in combination with not constraining large-scale conditions by spectral nudging results in lower WT skill. The selection of the driving global climate model (GCM) has a large effect on the skill of NA-CORDEX simulations but a smaller impact on the WRF36 runs. The formulation of the RCM is of minor importance except for capturing the variability within WTs. Changing the model physics or increasing the RCM horizontal grid spacing has little effect. These results highlight the importance of selecting GCMs with accurate synoptic-scale variability for downscaling and to find a balance between large domains that can result in biased WT representations and small domains that inhibit the realistic development of mesoscale processes. At the end of the century, monsoonal flow conditions increase systematically by up to 30% and a WT that is a significant source of moisture for the Northern Plains during the growing seasons decreases systematically up to –30%
BC4GO: a full-text corpus for the BioCreative IV GO task
Gene function curation via Gene Ontology (GO) annotation is a common task among Model Organism Database groups. Owing to its manual nature, this task is considered one of the bottlenecks in literature curation. There have been many previous attempts at automatic identification of GO terms and supporting information from full text. However, few systems have delivered an accuracy that is comparable with humans. One recognized challenge in developing such systems is the lack of marked sentence-level evidence text that provides the basis for making GO annotations. We aim to create a corpus that includes the GO evidence text along with the three core elements of GO annotations: (i) a gene or gene product, (ii) a GO term and (iii) a GO evidence code. To ensure our results are consistent with real-life GO data, we recruited eight professional GO curators and asked them to follow their routine GO annotation protocols. Our annotators marked up more than 5000 text passages in 200 articles for 1356 distinct GO terms. For evidence sentence selection, the inter-annotator agreement (IAA) results are 9.3% (strict) and 42.7% (relaxed) in F1-measures. For GO term selection, the IAAs are 47% (strict) and 62.9% (hierarchical). Our corpus analysis further shows that abstracts contain ∼10% of relevant evidence sentences and 30% distinct GO terms, while the Results/Experiment section has nearly 60% relevant sentences and >70% GO terms. Further, of those evidence sentences found in abstracts, less than one-third contain enough experimental detail to fulfill the three core criteria of a GO annotation. This result demonstrates the need of using full-text articles for text mining GO annotations. Through its use at the BioCreative IV GO (BC4GO) task, we expect our corpus to become a valuable resource for the BioNLP research community
Patterns of variability in Be/X-ray pulsars during giant outbursts
The discovery of source states in the X-ray emission of black-hole binaries
and neutron-star low-mass X-ray binaries constituted a major step forward in
the understanding of the physics of accretion onto compact objects. While there
are numerous studies on the correlated timing and spectral variability of these
systems, very little work has been done on high-mass X-ray binaries, the third
major type of X-ray binaries. The main goal of this work is to investigate
whether Be accreting X-ray pulsars display source states and characterise those
states through their spectral and timing properties. We have made a systematic
study of the power spectra, energy spectra and X-ray hardness-intensity
diagrams of nine Be/X-ray pulsars. The evolution of the timing and spectral
parameters were monitored through changes over two orders of magnitude in
luminosity. We find that Be/X-ray pulsars trace two different branches in the
hardness-intensity diagram: the horizontal branch corresponds to a
low-intensity state of the source and it is characterised by fast colour and
spectral changes and high X-ray variability. The diagonal branch is a
high-intensity state that emerges when the X-ray luminosity exceeds a critical
limit. The photon index anticorrelates with X-ray flux in the horizontal branch
but correlates with it in the diagonal branch. The correlation between QPO
frequency and X-ray flux reported in some pulsars is also observed if the peak
frequency of the broad-band noise that accounts for the aperiodic variability
is used. The two branches may reflect two different accretion modes, depending
on whether the luminosity of the source is above or below a critical value.
This critical luminosity is mainly determined by the magnetic field strength,
hence it differs for different sources.Comment: Complete missing words in title. Proof corrections adde
BeppoSAX observations of soft X-ray Intermediate Polars
We present broad-band (0.1--90keV) spectral and temporal properties of the
three Intermediate Polars, RE0751+144 (PQ Gem), RXJ0558.0+5353 (V405Aur) and
RXJ1712.6-2414 (V2400 Oph) based on simultaneous soft and hard X-ray
observations with the BeppoSAX satellite. The analysis of their spectra over
the wide energy range of BeppoSAX instruments allows us to identify the soft
and hard X-ray components and to determine simultaneously their temperatures.
The black--body temperatures of the irradiated poles of the white dwarf
atmosphere are found to be 60--100eV, much higher than those found in their
synchronous analogues, the Polars. The temperature of the optically thin
post--shock plasma is well constrained in RXJ1712.6-2414 and in RE0751+144 (13
and 17keV) and less precisely determined in RXJ0558.0+5353. In the first two
systems evidence of subsolar abundances is found, similarly to what estimated
in other magnetic Cataclysmic Variables. A Compton reflection component is
present in RXJ0558.0+5353 and in RE0751+144 and it is favoured in
RXJ1712.6-2414. Its origin is likely at the irradiated white dwarf surface.
Although these systems share common properties (soft X-ray component and
optical polarized radiation), their X-ray power spectra and light curves at
different energies suggest accretion geometries which cannot be reconciled with
a single and simple configuration.Comment: 12 pages, 15 postscript figures, LateX, uses aa.cls. Accepted for
publications in Astronomy and Astrophysics Main Journa
Real-world and natural history data for drug evaluation in Duchenne muscular dystrophy: suitability of the North Star Ambulatory Assessment for comparisons with external controls
Using external controls based on real-world or natural history data (RWD/NHD) for drug evaluations in Duchenne muscular dystrophy (DMD) is appealing given the challenges of enrolling placebo-controlled trials, especially for multi-year trials. Comparisons to external controls, however, face risks of bias due to differences in outcomes between trial and RWD/NHD settings. To assess this bias empirically, we conducted a multi-institution study comparing mean 48-week changes in North Star Ambulatory Assessment (NSAA) total score between trial placebo arms and RWD/NHD sources, with and without adjustment for baseline prognostic factors. Analyses used data from three placebo arms (235 48-week intervals, N = 235 patients) and three RWD/NHD sources (348 intervals, N = 202 patients). Differences in mean ΔNSAA between placebo arms and RWD/NHD sources were small before adjustment (-1.2 units, 95% CI: [-2.0 -0.5]) and were attenuated and no longer statistically significant after adjustment (0.1 units (95% CI: [-0.6, 0.8]). Results were similar whether adjusting using multivariable regression or propensity score matching. This consistency in ΔNSAA between trial placebo arms and RWD/NHD sources accords with prior findings for the six-minute walk distance, provides a well-validated framework for baseline adjustment of prognostic factors, and supports the suitability of RWD/NHD external controls for drug evaluations in ambulatory DMD
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