34 research outputs found
The VLTI / PIONIER near-infrared interferometric survey of southern T Tauri stars. I. First results
Context : The properties of the inner disks of bright Herbig AeBe stars have
been studied with near infrared (NIR) interferometry and high resolution
spectroscopy. The continuum and a few molecular gas species have been studied
close to the central star; however, sensitivity problems limit direct
information about the inner disks of the fainter T Tauri stars.
Aims : Our aim is to measure some of the properties of the inner regions of
disks surrounding southern T Tauri stars.
Methods : We performed a survey with the PIONIER recombiner instrument at
H-band of 21 T Tauri stars. The baselines used ranged from 11 m to 129 m,
corresponding to a maximum resolution of 3mas (0.45 au at 150 pc).
Results : Thirteen disks are resolved well and the visibility curves are
fully sampled as a function of baseline in the range 45-130 m for these 13
objects. A simple qualitative examination of visibility profiles allows us to
identify a rapid drop-off in the visibilities at short baselines in 8 resolved
disks. This is indicative of a significant contribution from an extended
contribution of light from the disk. We demonstrate that this component is
compatible with scattered light, providing strong support to a prediction made
by Pinte et al. (2008). The amplitude of the drop-off and the amount of dust
thermal emission changes from source to source suggesting that each disk is
different. A by-product of the survey is the identification of a new
milli-arcsec separation binary: WW Cha. Spectroscopic and interferometric data
of AK Sco have also been fitted with a binary and disk model.
Conclusions : Visibility data are reproduced well when thermal emission and
scattering form dust are fully considered. The inner radii measured are
consistent with the expected dust sublimation radii. Modelling of AK Sco
suggests a likely coplanarity between the disk and the binary's orbital planeComment: 19 pages, 11 figure
Phase Referencing in Optical Interferometry
One of the aims of next generation optical interferometric instrumentation is
to be able to make use of information contained in the visibility phase to
construct high dynamic range images. Radio and optical interferometry are at
the two extremes of phase corruption by the atmosphere. While in radio it is
possible to obtain calibrated phases for the science objects, in the optical
this is currently not possible. Instead, optical interferometry has relied on
closure phase techniques to produce images. Such techniques allow only to
achieve modest dynamic ranges. However, with high contrast objects, for faint
targets or when structure detail is needed, phase referencing techniques as
used in radio interferometry, should theoretically achieve higher dynamic
ranges for the same number of telescopes. Our approach is not to provide
evidence either for or against the hypothesis that phase referenced imaging
gives better dynamic range than closure phase imaging. Instead we wish to
explore the potential of this technique for future optical interferometry and
also because image reconstruction in the optical using phase referencing
techniques has only been performed with limited success. We have generated
simulated, noisy, complex visibility data, analogous to the signal produced in
radio interferometers, using the VLTI as a template. We proceeded with image
reconstruction using the radio image reconstruction algorithms contained in
AIPS IMAGR (CLEAN algorithm). Our results show that image reconstruction is
successful in most of our science cases, yielding images with a 4
milliarcsecond resolution in K band. (abridged)Comment: 11 pages, 36 figure
Phase Closure Image Reconstruction for Future VLTI Instrumentation
Classically, optical and near-infrared interferometry have relied on closure
phase techniques to produce images. Such techniques allow us to achieve modest
dynamic ranges. In order to test the feasibility of next generation optical
interferometers in the context of the VLTI-spectro-imager (VSI), we have
embarked on a study of image reconstruction and analysis. Our main aim was to
test the influence of the number of telescopes, observing nights and
distribution of the visibility points on the quality of the reconstructed
images. Our results show that observations using six Auxiliary Telescopes (ATs)
during one complete night yield the best results in general and is critical in
most science cases; the number of telescopes is the determining factor in the
image reconstruction outcome. In terms of imaging capabilities, an optical, six
telescope VLTI-type configuration and ~200 meter baseline will achieve 4 mas
spatial resolution, which is comparable to ALMA and almost 50 times better than
JWST will achieve at 2.2 microns. Our results show that such an instrument will
be capable of imaging, with unprecedented detail, a plethora of sources,
ranging from complex stellar surfaces to microlensing events.Comment: 11 pages, 26 figure
The Regibul Register: A Tool for Monitoring the Distribution and Incidence of Autoimmune Bullous Dermatoses in Three French Regions, 2010 to 2015
The Regibul Register: A Tool for Monitoring the Distribution and Incidence of Autoimmune Bullous Dermatoses in Three French Regions, 2010 to 2015
International audienceAutoimmune bullous dermatoses (AIBD) are rare in Western countries (1). The French Rare Diseases Reference Centre was set up in 2005, and encompasses 3 university hospital departments (Reims, Limoges and Rouen) located in 3 distinct French regions (Champagne-Ardenne, Limou-sin and Haute-Normandie) encompassing a total population of 3.9 million. The aim of the centre is to improve health-care, research, nursing staff and patient information, and to provide national and international recommendations. In this context, a computerized database was prospectively created in 2010, giving rise to the Regibul Register. Data from all new cases of AIBD seen in the reference centre were collected using an anonymous standardized questionnaire (CNIL authorization no. 911 0021). Despite diagnosis and treatment advances, to date only a few studies have described the distribution and incidence of sub-epidermal AIBD (2-10, Table SI 1) and pemphigus (11, 12). Using data collected over a 6-year period (2010 to 2015) from the 3 reference centre sites, the aim was to describe clinical characteristics along with the initial management of included patients (primary objective), and to estimate both the distribution and standardized incidence rates of these AIBD after exclusion of patients who were not living in our 3 regions (secondary objective)
Direct determination of physical parameters for main sequence stars
The environment of planetary formation and evolution is mainly characterized by its host star's physical properties. Until recently most fundamental stellar parameters, like e. g. the star's radius and effective temperature, have only been estimated indirectly; but with advances in interferometric observing technique it is now possible to obtain a direct estimate of them. In this poster we present preliminary results from measured interferometric fringe visibilities of main-sequence stars. These visibilities were collected using the four-beam combiner VLTI/PIONIER instrument and the 1.8m Auxiliary Telescopes (ATs) in A1-G1-K0-J3 quadruplet configuration. We bracketed each science target with different calibrators to ensure reducing the systematic errors in our data. For each target star, the data reduction was performed several hundred times, each time randomizing the set of fringes by the bootstrap method and the calibrators' diameters. This allowed us to take into account error correlations across spectral channels, between consecutive observations, and overnight. Each result was least-squares fitted by a uniform disc, yielding a value for the target's diameter. From the distribution of diameters we assessed the statistical error in the respective measurement. Using the HIPPARCOS parallax we estimated the distance and obtained the star's linear radius. Combined with the bolometric flux we obtained a direct quantification of the effective temperature from the Stefan-Boltzmann equation. Finally, these direct determinations of stellar radii and effective temperatures enable us to better characterize planets around main-sequence stars
No impact of passive smoke on the somatic profile of lung cancers in never-smokers
International audienceEGFR and HER2 mutations and ALK rearrangement are known to be related to lung cancer in never-smokers, while KRAS, BRAF and PIK3CA mutations are typically observed among smokers. There is still debate surrounding whether never-smokers exposed to passive smoke exhibit a "smoker-like" somatic profile compared with unexposed never-smokers. Passive smoke exposure was assessed in the French BioCAST/IFCT-1002 never-smoker lung cancer cohort and routine molecular profiles analyses were compiled. Of the 384 patients recruited into BioCAST, 319 were tested for at least one biomarker and provided data relating to passive smoking. Overall, 219 (66%) reported having been exposed to passive smoking. No significant difference was observed between mutation frequency and passive smoke exposure (EGFR mutation: 46% in never exposed versus 41% in ever exposed; KRAS: 7% versus 7%; ALK: 13% versus 11%; HER2: 4% versus 5%; BRAF: 6% versus 5%; PIK3CA: 4% versus 2%). We observed a nonsignificant trend for a negative association between EGFR mutation and cumulative duration of passive smoke exposure. No association was found for other biomarkers. There is no clear association between passive smoke exposure and somatic profile in lifelong, never-smoker lung cancer
Recommandations pour la prise en charge buccodentaire des patients atteints de maladies bulleuses auto-immunes avec atteinte buccale
International audienc
Incidence and Mortality of Pemphigus in France
International audienceNo abstract availabl