221 research outputs found
A new type of photoionized code required for the new era of X-ray spectroscopy
With the advent of the present and future spatial X-ray missions, it becomes
crucial to model correctly the line spectrum of X-ray emitting media. We have
built a photoionization code, Titan, solving the transfer of a thousand lines
and of the continuum with the "Accelerated Lambda Iteration" method, which is
most reliable for line transfer. In all other photoionization codes the line
intensities are computed with the so-called "escape probability formalism",
used in its simplest approximation. In a previous paper (Dumont et al. 2003),
it was shown that this approximation leads to errors which can exceed one order
of magnitude in the case a Thomson thickness of the order of unity. We show
here that it also happens in the case of a Thomson thickness of 0.001 to 0.1.
The errors on the line fluxes and line ratios are of the order of 30% for a
column density of 10^{20} cm^{-2}, and a factor five for a column density of
10^{23} cm^{-2}, in conditions appropriate for Seyfert 2 and for the Warm
Absorber of Seyfert 1.Comment: 11 pages, 7 figures. accepted by A&
Investigating the mass of the intermediate mass black hole candidate HLX-1 with the SLIMBH model
In this paper we present a comprehensive study of the mass of the
intermediate mass black hole candidate HLX-1 in the galaxy ESO 243-49. We
analyse the continuum X-ray spectra collected by Swift, XMM-Newton, and Chandra
with the slim disc model, SLIMBH, and estimate the black hole mass for the full
range of inclination (inc = 0{\deg} - 85{\deg}) and spin (a* = 0 - 0.998). The
relativistic SLIMBH model is particularly suited to study high luminosity disc
spectra as it incorporates the effects of advection, such as the shift of the
inner disc edge towards smaller radii and the increasing height of the disc
photosphere (including relativistic ray-tracing from its proper location rather
than the mid-plane of the disc). We find for increasing values of inclination
that a zero spin black hole has a mass range of 6,300 - 50,900 M_sun and a
maximally spinning black hole has a mass between 16,900 - 191,700 M_sun. This
is consistent with previous estimates and reinforces the idea that HLX-1
contains an intermediate mass black hole.Comment: updated version, published in Astronomy and Astrophysic
A search for hyperluminous X-ray sources in the XMM-Newton source catalog
We present a new method to identify luminous off-nuclear X-ray sources in the
outskirts of galaxies from large public redshift surveys, distinguishing them
from foreground and background interlopers. Using the 3XMM-DR5 catalog of X-ray
sources and the SDSS DR12 spectroscopic sample of galaxies, with the help of
this off-nuclear cross-matching technique, we selected 98 sources with inferred
X-ray luminosities in the range , compatible with hyperluminous X-ray objects (HLX). To validate
the method, we verify that it allowed us to recover known HLX candidates such
as ESO 24349 HLX1 and M82 X1. From a statistical study, we
conservatively estimate that up to of these sources may be fore- or
background sources, statistically leaving at least 16 that are likely to be
HLXs, thus providing support for the existence of the HLX population. We
identify two good HLX candidates and using other publicly available datasets,
in particular the VLA FIRST in radio, UKIDSS in the near-infrared, GALEX in the
ultra-violet and CFHT Megacam archive in the optical, we present evidence that
these objects are unlikely to be foreground or background X-ray objects of
conventional types, e.g. active galactic nuclei, BL Lac objects, Galactic X-ray
binaries or nearby stars. However, additional dedicated X-ray and optical
observations are needed to confirm their association with the assumed host
galaxies and thus secure their HLX classification.Comment: 20 pages, 6 figures, accepted to Ap
De la rédaction assistée à l'appréhension syntaxique : comment le numérique peut éclairer la compréhension de la langue
International audienceDe la rĂ©daction assistĂ©e Ă lâapprĂ©hension syntaxiqueComment rendre sensible la notion de syntagme et de fonction grammaticale en sâaffranchissant de la question terminologique ? Les programmes de 2015 insistent sur lâimportance des manipulations pour mettre en Ă©vidence lâorganisation syntaxique tout en Ă©vitant lâinflation terminologique 1. Ils prĂ©conisent Ă cet effet lâutilisation du TNI ou du traitement de texte. Comment cet outil peut-il faciliter la production de texte en rendant perceptibles la cohĂ©sion dessyntagmes, ainsi que les principes dâorganisation de la phrase et de progression textuelle ? Câest ce que nous avons cherchĂ© Ă mettre en Ă©vidence
Radio Detections During Two State Transitions of the Intermediate Mass Black Hole HLX-1
Relativistic jets are streams of plasma moving at appreciable fractions of
the speed of light. They have been observed from stellar mass black holes
(320 solar masses, M) as well as supermassive black holes
(1010 M) found in the centres of most galaxies. Jets
should also be produced by intermediate mass black holes (1010
M), although evidence for this third class of black hole has until
recently been weak. We report the detection of transient radio emission at the
location of the intermediate mass black hole candidate ESO 243-49 HLX-1, which
is consistent with a discrete jet ejection event. These observations also allow
us to refine the mass estimate of the black hole to be between 9
10 M and 9 10 M.Comment: 13 pages, includes supplementary online information. Published in
Science in August 201
X-ray Variability and Hardness of ESO 243-49 HLX-1: Clear Evidence for Spectral State Transitions
The ultra-luminous X-ray (ULX) source ESO 243-49 HLX-1 currently provides the
strongest evidence for the existence of intermediate mass black holes. We
conduct an ongoing monitoring campaign with the Swift X-ray Telescope and found
that HLX-1 showed two fast rise and exponential decay with increases in the
count rate of a factor ~40 separated by 375+/-13 days. We obtained new
XMM-Newton and Chandra dedicated pointings that were triggered at the lowest
and highest luminosities, respectively. The unabsorbed luminosities ranged from
1.9x10^40 to 1.25x10^42 erg/s. We confirm here the detection of spectral state
transitions from HLX-1 reminiscent of Galactic black hole binaries: at high
luminosities, the X-ray spectrum showed a thermal state dominated by a disk
component with temperatures of 0.26 keV at most, and at low luminosities the
spectrum is dominated by a hard power law with a photon index in the range
1.4-2.1, consistent with a hard state. The source was also observed in a steep
power law state. In the thermal state, the luminosity of the disk component
appears to scale with the fourth power of the inner disk temperature which
supports the presence of an optically thick, geometrically thin accretion disk.
The low fractional variability (rms of 9+/-9%) in this state also suggests the
presence of a dominant disk. The spectral changes and long-term variability of
the source cannot be explained by variations of the beaming angle and are not
consistent with the source being in a super-Eddington accretion state. HLX-1 is
thus an unusual ULX as it is similar to Galactic black hole binaries, which
have non-beamed and sub-Eddington emission, but with luminosities 3 orders of
magnitude higher. In this picture, a lower limit on the mass of the black hole
of >9000 M_sun can be derived, and the disk temperature in the thermal state
also suggests the presence of a black hole of a few 10^3 M_sun.Comment: accepted for publication in ApJ (October 10, 2011, v740-1); 11
figures, 13 pages with emulateapj styl
Severe Occupational Asthma : Insights From a Multicenter European Cohort
BACKGROUND: Although sensitizer-induced occupational asthma (OA) accounts for an appreciable fraction of adult asthma, the severity of OA has received little attention. OBJECTIVE: The aim of this study was to characterize the burden and determinants of severe OA in a large multicenter cohort of subjects with OA. METHODS: This retrospective study included 997 subjects with OA ascertained by a positive specific inhalation challenge completed in 20 tertiary centers in 11 European countries during the period 2006 to 2015. Severe asthma was defined by a high level of treatment and any 1 of the following criteria: (1) daily need for a reliever medication, (2) 2 or more severe exacerbations in the previous year, or (3) airflow obstruction. RESULTS: Overall, 162 (16.2%; 95% CI, 14.0%-18.7%) subjects were classified as having severe OA. Multivariable logistic regression analysis revealed that severe OA was associated with persistent (vs reduced) exposure to the causal agent at work (odds ratio [OR], 2.78; 95% CI, 1.50-5.60); a longer duration of the disease (OR, 1.04; 95% CI, 1.00-1.07); a low level of education (OR, 2.69; 95% CI, 1.73-4.18); childhood asthma (OR, 2.92; 95% CI, 1.13-7.36); and sputum production (OR, 2.86; 95% CI, 1.87-4.38). In subjects removed from exposure, severe OA was associated only with sputum production (OR, 3.68; 95% CI, 1.87-7.40); a low education level (OR, 3.41; 95% CI, 1.72-6.80); and obesity (OR, 1.98; 95% CI, 0.97-3.97). CONCLUSIONS: This study indicates that a substantial proportion of subjects with OA experience severe asthma and identifies potentially modifiable risk factors for severe OA that should be targeted to reduce the adverse impacts of the disease. (C) 2019 Published by Elsevier Inc. on behalf of the American Academy of Allergy, Asthma & ImmunologyPeer reviewe
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