3,958 research outputs found
On the apparent absence of broad iron lines in Seyfert galaxies
We present an analysis of XMM-Newton observations of eleven Seyfert galaxies
that appear to be missing a broad iron K alpha line. These objects represent a
challenge to the established paradigm for active galactic nuclei, where a
relatively cold accretion disc feeds the central black hole. In that paradigm,
X-ray illumination of the accretion disc should lead to continuum and
fluorescence emission from iron which is broadened and shifted by relativistic
effects close the hole. We extend the work of Nandra et al. (2007), who found
no evidence for such a component in an earlier analysis of these objects, by
testing a variety of more complex relativistic reflection models. Specifically,
we consider the possibility that the disc is highly ionised, and/or that the
the reflection is heavily blurred by strong relativistic effects in a Kerr
geometry. We find that in 8/11 of the observations with no apparent broad iron
line, the fit is significantly improved when an ionised or strongly blurred
reflector is included, and that all 11 observations allow for such a component.
The disc inclinations are found generally to be around 60 degrees, which when
combined with a steep emissivity profile results in strong relativistic
blurring of the reflection, rendering the K alpha line difficult to distinguish
from the underlying continuum. Nevertheless, relativistic reflection does
appear to be present, and the strength of the smeared reflection is similar to
that expected from a flat disc illuminated by a point source. Such blurred
reflection and the associated steep radial emissivity profiles are consistent
with the gravitational light bending of the continuum photons close to the
black hole.Comment: 9 pages, 2 figures. Accepted for publication in MNRA
A Variable-Density Absorption Event in NGC 3227 mapped with Suzaku and Swift
The morphology of the circumnuclear gas accreting onto supermassive black
holes in Seyfert galaxies remains a topic of much debate. As the innermost
regions of Active Galactic Nuclei (AGN) are spatially unresolved, X-ray
spectroscopy, and in particular line-of-sight absorption variability, is a key
diagnostic to map out the distribution of gas. Observations of variable X-ray
absorption in multiple Seyferts and over a wide range of timescales indicate
the presence of clumps/clouds of gas within the circumnuclear material. Eclipse
events by clumps transiting the line of sight allow us to explore the
properties of the clumps over a wide range of radial distances from the
optical/UV Broad Line Region (BLR) to beyond the dust sublimation radius.
Time-resolved absorption events have been extremely rare so far, but suggest a
range of density profiles across Seyferts. We resolve a weeks-long absorption
event in the Seyfert NGC 3227. We examine six Suzaku and twelve Swift
observations from a 2008 campaign spanning 5 weeks. We use a model accounting
for the complex spectral interplay of three differently-ionized absorbers. We
perform time-resolved spectroscopy to discern the absorption variability
behavior. We also examine the IR-to-X-ray spectral energy distribution (SED) to
test for reddening by dust. The 2008 absorption event is due to
moderately-ionized () gas covering 90% of the line of
sight. We resolve the density profile to be highly irregular, in contrast to a
previous symmetric and centrally-peaked event mapped with RXTE in the same
object. The UV data do not show significant reddening, suggesting that the
cloud is dust-free. The 2008 campaign has revealed a transit by a filamentary,
moderately-ionized cloud of variable density that is likely located in the BLR,
and possibly part of a disk wind.Comment: Accepted for publication by A&
FERO: Finding Extreme Relativistic Objects. I. Statistics of Relativistic Fe Kalpha lines in Radio-Quiet Type 1 AGN
Accretion models predict that fluorescence lines broadened by relativistic
effects should arise from reflection of X-ray emission onto the inner region of
the accretion disc surrounding the central black hole of active galactic nuclei
(AGN). The theory behind the origin of relativistic lines is well established,
and observational evidence from a moderate number of sources seems to support
the existence of these lines. The aim of this work is to establish the fraction
of AGN with relativistic Fe Kalpha lines, and study possible correlations with
source physical properties. An XMM-Newton collection of 149 radio-quiet Type 1
AGN has been systematically and uniformly analyzed in order to search for
significant evidence of a relativistically broadened Fe Kalpha line. To enable
statistical studies, an almost complete, flux-limited subsample of 31 sources
has been defined. The 2-10 keV spectra of the FERO sources have been compared
with a complex model including most of the physical components observed in the
X-ray spectra of Seyfert galaxies: a power law primary continuum modified by
non-relativistic Compton reflection and warm absorption, plus a series of
narrow Fe line reflection features. The observed fraction of sources in the
flux-limited sample that show significant evidence of a relativistic Fe Kalpha
line is 36%. The average line Equivalent Width (EW) is of the order of 100 eV,
while the average disc inclination angle is 28+/-5 deg and the average
power-law index of the radial disc emissivity law is 2.4+/-0.4. The spin value
is well constrained only in 2 cases (MCG-6-30-15 and MRK509), and in the rest
of the cases, whenever a constraint can be placed, it always implies the
rejection of the static black hole solution. The Fe Kalpha line EW does not
correlate with disc parameters or with system physical properties, such as
black hole mass, accretion rate and hard X-ray luminosity.Comment: 22 pages, 7 figures. Accepted for publication in A&
Accretion, ejection and reprocessing in supermassive black holes
This is a White Paper in support of the mission concept of the Large
Observatory for X-ray Timing (LOFT), proposed as a medium-sized ESA mission. We
discuss the potential of LOFT for the study of active galactic nuclei. For a
summary, we refer to the paper.Comment: White Paper in Support of the Mission Concept of the Large
Observatory for X-ray Timin
IFNβ Protects Neurons from Damage in a Murine Model of HIV-1 Associated Brain Injury.
Infection with human immunodeficiency virus-1 (HIV-1) causes brain injury. Type I interferons (IFNα/β) are critical mediators of any anti-viral immune response and IFNβ has been implicated in the temporary control of lentiviral infection in the brain. Here we show that transgenic mice expressing HIV-1 envelope glycoprotein 120 in their central nervous system (HIVgp120tg) mount a transient IFNβ response and provide evidence that IFNβ confers neuronal protection against HIVgp120 toxicity. In cerebrocortical cell cultures, neuroprotection by IFNβ against gp120 toxicity is dependent on IFNα receptor 1 (IFNAR1) and the β-chemokine CCL4, as IFNAR1 deficiency and neutralizing antibodies against CCL4, respectively, abolish the neuroprotective effects. We find in vivo that IFNβ mRNA is significantly increased in HIVgp120tg brains at 1.5, but not 3 or 6 months of age. However, a four-week intranasal IFNβ treatment of HIVgp120tg mice starting at 3.5 months of age increases expression of CCL4 and concomitantly protects neuronal dendrites and pre-synaptic terminals in cortex and hippocampus from gp120-induced damage. Moreover, in vivo and in vitro data suggests astrocytes are a major source of IFNβ-induced CCL4. Altogether, our results suggest exogenous IFNβ as a neuroprotective factor that has potential to ameliorate in vivo HIVgp120-induced brain injury
Religion and returns in Europe
Drawing on social identity and social impact theory, this paper is the first to investigate the impact of religious preferences on share prices and expected returns at the country level. Using data from 12 European countries, our findings suggest that religion has a significant effect on the share price of companies whose activities are considered unethical, i.e., tobacco manufacturers and alcohol producers. The share price of these companies (called sin stocks) is depressed when they are located in a predominantly Protestant environment (relative to a Catholic environment). With investors in Protestant countries being more sin averse than in Catholic countries, they insist upon higher expected returns on sin stocks. Conversely, religious preferences do not have the same impact on the performance of other companies, e.g. socially responsible companies. Our results are robust to various methodologies and controlling for several firm-specific, industry-specific and country-specific characteristics
Identifying DNA methylation biomarkers for non-endoscopic detection of Barrett’s esophagus
We report a biomarker-based non-endoscopic method for detecting Barrett’s esophagus (BE), based on detecting methylated DNAs retrieved via a swallowable balloon-based esophageal sampling device. BE is the precursor of, and a major recognized risk factor for, developing esophageal adenocarcinoma (EAC). Endoscopy, the current standard for BE detection, is not cost-effective for population screening. We performed genome-wide screening to ascertain regions targeted for recurrent aberrant cytosine methylation in BE, identifying high-frequency methylation within the CCNA1 locus. We tested CCNA1 DNA methylation as a BE biomarker in cytology brushings of the distal esophagus from 173 individuals with or without BE. CCNA1 DNA methylation demonstrated an area under the curve (AUC)=0.95 for discriminating BE-related metaplasia and neoplasia cases versus normal individuals, performing identically to methylation of VIM DNA, an established BE biomarker. When combined, the resulting two biomarker panel was 95% sensitive and 91% specific. These results were replicated in an independent validation cohort of 149 individuals, who were assayed using the same cutoff values for test positivity established in the training population. To progress toward non-endoscopic esophageal screening, we engineered a well-tolerated, swallowable, encapsulated balloon device able to selectively sample the distal esophagus within 5 minutes. In balloon samples from 86 individuals, tests of CCNA1 plus VIM DNA methylation detected BE metaplasia with 90.3% sensitivity and 91.7% specificity. Combining the balloon sampling device with molecular assays of CCNA1 plus VIM DNA methylation enables an efficient, well-tolerated, sensitive, and specific method of screening at-risk populations for BE
The INTEGRAL/IBIS AGN catalogue I: X-ray absorption properties versus optical classification
In this work we present the most comprehensive INTEGRAL AGN sample which
lists 272 objects. Here we mainly use this sample to study the absorption
properties of active galaxies, to probe new AGN classes and to test the AGN
unification scheme. We find that half (48%) of the sample is absorbed while the
fraction of Compton thick AGN is small (~7%). In line with our previous
analysis, we have however shown that when the bias towards heavily absorbed
objects which are lost if weak and at large distance is removed, as it is
possible in the local Universe, the above fractions increase to become 80% and
17%. We also find that absorption is a function of source luminosity, which
implies some evolution in the obscuration properties of AGN. Few peculiar
classes, so far poorly studied in the hard X-ray band, have been detected and
studied for the first time such as 5 XBONG, 5 type 2 QSOs and 11 LINERs. In
terms of optical classification, our sample contains 57% of type 1 and 43% of
type 2 AGN; this subdivision is similar to that found in X-rays if unabsorbed
versus absorbed objects are considered, suggesting that the match between
optical and X-ray classification is overall good. Only a small percentage of
sources (12%) does not fulfill the expectation of the unified theory as we find
22 type 1 AGN which are absorbed and 10 type 2 AGN which are unabsorbed.
Studying in depth these outliers we found that most of the absorbed type 1 AGN
have X-ray spectra characterized by either complex or warm/ionized absorption
more likely due to ionized gas located in an accretion disk wind or in the
biconical structure associated to the central nucleus, therefore unrelated to
the toroidal structure. Among 10 type 2 AGN which resulted to be unabsorbed, at
most 3-4% is still eligible to be classified as a "true" type 2 AGN.Comment: 21 pages, 6 figures, 5 tables. Accepted for publication on MNRAS.
arXiv admin note: text overlap with arXiv:0709.2077 by other author
Display of probability densities for data from a continuous distribution
Based on cumulative distribution functions, Fourier series expansion and
Kolmogorov tests, we present a simple method to display probability densities
for data drawn from a continuous distribution. It is often more efficient than
using histograms.Comment: 5 pages, 4 figures, presented at Computer Simulation Studies XXIV,
Athens, GA, 201
Poly-ICLC, a TLR3 Agonist, Induces Transient Innate Immune Responses in Patients With Treated HIV-Infection: A Randomized Double-Blinded Placebo Controlled Trial
Objective: Toll-like receptor-3 agonist Poly-ICLC has been known to activate immune cells and induce HIV replication in pre-clinical experiments. In this study we investigated if Poly-ICLC could be used for disrupting HIV latency while simultaneously enhancing innate immune responses.Design: This was a randomized, placebo-controlled, double-blinded trial in aviremic, cART-treated HIV-infected subjects. Participants (n = 15) were randomized 3:1 to receive two consecutive daily doses of Poly-ICLC (1.4 mg subcutaneously) vs. placebo. Subjects were observed for adverse events, immune activation, and viral replication.Methods: Besides primary outcomes of safety and tolerability, several longitudinal immune parameters were evaluated including immune cell phenotype and function via flowcytometry, ELISA, and transcriptional profiling. PCR assays for plasma HIV-1 RNA, CD4+ T cell-associated HIV-1 RNA, and proviral DNA were performed to measure HIV reservoirs and latency.Results: Poly-ICLC was overall safe and well-tolerated. Poly-ICLC-related adverse events were Grade 1/2, with the exception of one Grade 3 neutropenia which was short-lived. Mild Injection site reactions were observed in nearly all participants in the Poly-ICLC arm. Transcriptional analyses revealed upregulation of innate immune pathways in PBMCs following Poly-ICLC treatment, including strong interferon signaling accompanied by transient increases in circulating IP-10 (CXCL10) levels. These responses generally peaked by 24–48 h after the first injection and returned to baseline by day 8. CD4+ T cell number and phenotype were unchanged, plasma viral control was maintained and no significant effect on HIV reservoirs was observed.Conclusions: These finding suggest that Poly-ICLC could be safely used for inducing transient innate immune responses in treated HIV+ subjects indicating promise as an adjuvant for HIV therapeutic vaccines.Trial Registration:www.ClinicalTrials.gov, identifier: NCT02071095
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