42 research outputs found
Masses of the components of SB2 binaries observed with Gaia. II. Masses derived from PIONIER interferometric observations for Gaia validation
In anticipation of the Gaia astrometric mission, a sample of spectroscopic
binaries is being observed since 2010 with the Sophie spectrograph at the
Haute--Provence Observatory. Our aim is to derive the orbital elements of
double-lined spectroscopic binaries (SB2s) with an accuracy sufficient to
finally obtain the masses of the components with relative errors as small as 1
% when combined with Gaia astrometric measurements. In order to validate the
masses derived from Gaia, interferometric observations are obtained for three
SB2s in our sample with F-K components: HIP 14157, HIP 20601 and HIP 117186.
The masses of the six stellar components are derived. Due to its edge-on
orientation, HIP 14157 is probably an eclipsing binary. We note that almost all
the derived masses are a few percent larger than the expectations from the
standard spectral-type-mass calibration and mass-luminosity relation. Our
calculation also leads to accurate parallaxes for the three binaries, and the
Hipparcos parallaxes are confirmed.Comment: 10 pages, 3 figures, accepted by MNRA
Consistent dust and gas models for protoplanetary disks:IV. A panchromatic view of protoplanetary disks
Consistent Dust and Gas Models for Protoplanetary Disks:III. Models for Selected Objects from the FP7 DIANA Project
Consistent Dust and Gas Models for Protoplanetary Disks. III. Models for Selected Objects from the FP7 DIANA Project
The European FP7 project DIANA has performed a coherent analysis of a large set of observational data of protoplanetary disks by means of thermo-chemical disk models. The collected data include extinction-corrected stellar UV and X-ray input spectra (as seen by the disk), photometric fluxes, low and high resolution spectra, interferometric data, emission line fluxes, line velocity profiles and line maps, which probe the dust, polycyclic aromatic hydrocarbons (PAHs) and the gas in these objects. We define and apply a standardized modeling procedure to fit these data by state-of-the-art modeling codes (ProDiMo, MCFOST, MCMax), solving continuum and line radiative transfer (RT), disk chemistry, and the heating and cooling balance for both the gas and the dust. 3D diagnostic RT tools (e.g., FLiTs) are eventually used to predict all available observations from the same disk model, the DIANA-standard model. Our aim is to determine the physical parameters of the disks, such as total gas and dust masses, the dust properties, the disk shape, and the chemical structure in these disks. We allow for up to two radial disk zones to obtain our best-fitting models that have about 20 free parameters. This approach is novel and unique in its completeness and level of consistency. It allows us to break some of the degeneracies arising from pure Spectral Energy Distribution (SED) modeling. In this paper, we present the results from pure SED fitting for 27 objects and from the all inclusive DIANA-standard models for 14 objects. Our analysis shows a number of Herbig Ae and T Tauri stars with very cold and massive outer disks which are situated at least partly in the shadow of a tall and gas-rich inner disk. The disk masses derived are often in excess to previously published values, since these disks are partially optically thick even at millimeter wavelength and so cold that they emit less than in the Rayleigh–Jeans limit. We fit most infrared to millimeter emission line fluxes within a factor better than 3, simultaneously with SED, PAH features and radial brightness profiles extracted from images at various wavelengths. However, some line fluxes may deviate by a larger factor, and sometimes we find puzzling data which the models cannot reproduce. Some of these issues are probably caused by foreground cloud absorption or object variability. Our data collection, the fitted physical disk parameters as well as the full model output are available to the community through an online database (http://www.univie.ac.at/diana)
Consistent dust and gas models for protoplanetary disks IV. A panchromatic view of protoplanetary disks
Context. Consistent modeling of protoplanetary disks requires the simultaneous solution of both continuum and line radiative transfer, heating and cooling balance between dust and gas and, of course, chemistry. Such models depend on panchromatic observations that can provide a complete description of the physical and chemical properties and energy balance of protoplanetary systems. Along these lines, we present a homogeneous, panchromatic collection of data on a sample of 85 T Tauri and Herbig Ae objects for which data cover a range from X-rays to centimeter wavelengths. Datasets consist of photometric measurements, spectra, along with results from the data analysis such as line fluxes from atomic and molecular transitions. Additional properties resulting from modeling of the sources such as disk mass and shape parameters, dust size, and polycyclic aromatic hydrocarbon (PAH) properties are also provided for completeness.
Aim. The purpose of this data collection is to provide a solid base that can enable consistent modeling of the properties of protoplanetary disks. To this end, we performed an unbiased collection of publicly available data that were combined to homogeneous datasets adopting consistent criteria. Targets were selected based on both their properties and the availability of data.
Methods. Data from more than 50 different telescopes and facilities were retrieved and combined in homogeneous datasets directly from public data archives or after being extracted from more than 100 published articles. X-ray data for a subset of 56 sources represent an exception as they were reduced from scratch and are presented here for the first time.
Results. Compiled datasets, along with a subset of continuum and emission-line models are stored in a dedicated database and distributed through a publicly accessible online system. All datasets contain metadata descriptors that allow us to track them back to their original resources. The graphical user interface of the online system allows the user to visually inspect individual objects but also compare between datasets and models. It also offers to the user the possibility to download any of the stored data and metadata for further processing
A 'Rosetta Stone' for protoplanetary disks:the synergy of multi-wavelength observations
The recent progress in instrumentation and telescope development has brought
us different ways to observe protoplanetary disks, including interferometers,
space missions, adaptive optics, polarimetry, and time- and spectrally-resolved
data. While the new facilities have changed the way we can tackle the existing
open problems in disk structure and evolution, there is a substantial lack of
interconnection between different observing techniques and their user
communities. Here, we explore the complementarity of some of the
state-of-the-art observing techniques, and how they can be brought together in
a collective effort to understand how disks evolve and disperse at the time of
planet formation.
This paper was born at the "Protoplanetary Discussions" meeting in Edinburgh,
2016. Its goal is to clarify where multi-wavelength observations of disks
converge in unveiling disk structure and evolution, and where they diverge and
challenge our current understanding. We discuss caveats that should be
considered when linking results from different observations, or when drawing
conclusions based on limited datasets (in terms of wavelength or sample). We
focus on disk properties that are currently being revolutionized by
multi-wavelength observations. Specifically: the inner disk radius, holes and
gaps and their link to large-scale disk structures, the disk mass, and the
accretion rate. We discuss how the links between them, as well as the apparent
contradictions, can help us to disentangle the disk physics and to learn about
disk evolution.Comment: Accepted for publication in PASA. 37 pages, 9 figures, 1 table.
Revised version: corrected problem in Fig
First light for GRAVITY: Phase referencing optical interferometry for the Very Large Telescope Interferometer
Integration of Pore Features into the Evaluation of Fingerprint Evidence
Fingerprint practitioners rely on level 3 features to make decisions in relation to the source of an unknown friction ridge skin impression. This research proposes to assess the strength of evidence associated with pores when shown in (dis)agreement between a mark and a reference print. Based upon an algorithm designed to automatically detect pores, a metric is defined in order to compare different impressions. From this metric, the weight of the findings is quantified using a likelihood ratio. The results obtained on four configurations and 54 donors show the significant contribution of the pore features and translate into statistical terms what latent fingerprint examiners have developed holistically through experience. The system provides LRs that are indicative of the true state under both the prosecution and the defense propositions. Not only such a system brings transparency regarding the weight to assign to such features, but also forces a discussion in relation to the risks of such a model to mislead
Etude géologique des terrains cristallins de Ligugé (Vienne) et de leur contexte sédimentaire. Cartographie, structure et signification du "horst" dans le détroit du Poitou
87e Congrès des Sociétés Savantes, 1962L’étude du horst de Ligugé présente un intérêt particulier en raison de sa situation géographique dans le seuil du Poitou à mi-distance entre le Massif Central et le Massif Vendéen.Nous avons essayé par différentes méthodes (cartographie détaillée, étude structurologique et tectonique) de préciser les rapports entre les terrains cristallins de Ligugé et les formations analogues de la Vendée et du Limousin, ainsi que les relations du socle primaire avec sa couverture sédimentaire. Les résultats obtenus de cette façon complètent les nombreuses observations antérieures sur ce secteur déjà très bien étudié, notamment par Briotey et Garran (1843), A. Le Touze de Longuemar (1859, 1867, 1870, 1876), J. Welsch (1892, 1895, 1903, 1927), P. A. Gillard (1929, 1938, 1941) et G. Mathieu (1952, 1953, 1959)