426 research outputs found
Spatially resolved PAH emission in the inner disks of Herbig Ae/Be stars
We present adaptive optics high angular resolution (\sim0.1\arcsec)
spectroscopic observations in the 3 \um region of eight well known Herbig Ae/Be
stars with circumstellar disks. We detect the aromatic emission feature at 3.3
\um for four out of six of our objects with flared disks (HD 169142, HD 97048,
HD 100453, HD 100546), some weaker additional features at 3.4 and 3.46 m
and nanodiamond features at 3.43 and 3.53 \um in two of our flared object (HD
100546 and HD 97048 respectively). We also detect hydrogen recombination line
at 3.74 \um in practically all objects. The emission in the polycyclic aromatic
hydrocarbons (PAHs) feature at 3.3 \um, additional and nanodiamond features in
the 3.4-3.5 \um region is, for the first time, spatially resolved in all the
sources where the features are detected. The full-width at half-maximum sizes
that we derive are typical of emission arising in a circumstellar disk. On the
other hand, the continuum emission is unresolved, with the exception of HD
97048 where it is marginally resolved. We compare the observed spatial
distribution of the 3.3 m PAH feature and the adjacent continuum to the
predictions of a disk model that includes transiently heated small grains and
PAHs in addition to large grains in thermal equilibrium \cite[]{habart2004a}.
The model predicts that, as observed, the 3.3 m PAH emission feature is
significantly broader than that of the adjacent continuum and that about 50% of
its integrated intensity comes from a radius 30 AU. We find that the
predicted brightness profiles reproduce very well the observed ones. This
proves beyond doubt that the energetic 3.3 m PAH emission feature takes
its origin in the inner disk regions.Comment: 7 figures, accepted to A&
Astronomical Imaging⊠Atmospheric Turbulence? Adaptive Optics!
This book is a collection of 19 articles which reflect the courses given at the CollĂšge de France/Summer school âReconstruction d'images â Applications astrophysiquesâ held in Nice and FrĂ©jus, France, from June 18 to 22, 2012. The articles presented in this volume address emerging concepts and methods that are useful in the complex process of improving our knowledge of the celestial objects, including Earth
Diamonds in HD 97048
We present adaptive optics high angular resolution (\sim0\farcs1)
spectroscopic observations in the 3 m region of the Herbig Ae/Be star HD
97048. For the first time, we spatially resolve the emission in the diamond
features at 3.43 and 3.53 m and in the adjacent continuum. Using both the
intensity profiles along the slit and reconstructed two-dimensional images of
the object, we derive full-width at half-maximum sizes consistent with the
predictions for a circumstellar disk seen pole-on. The diamond emission
originates in the inner region ( AU) of the disk.Comment: ApJLetter, in pres
The self-coherent camera as a focal plane fine phasing sensor
Direct imaging of Earth-like exoplanets requires high contrast imaging
capability and high angular resolution. Primary mirror segmentation is a key
technological solution for large-aperture telescopes because it opens the path
toward significantly increasing the angular resolution. The segments are kept
aligned by an active optics system that must reduce segment misalignments below
tens of nm RMS to achieve the high optical quality required for astronomical
science programs. The development of cophasing techniques is mandatory for the
next generation of space- and ground-based segmented telescopes, which both
share the need for increasing spatial resolution. We propose a new focal plane
cophasing sensor that exploits the scientific image of a coronagraphic
instrument to retrieve simultaneously piston and tip-tilt misalignments. The
self-coherent camera phasing sensor (SCC-PS) adequately combines the SCC
properties to segmented telescope architectures with adapted segment
misalignment estimators and image processing. An overview of the system
architecture, and a thorough performance and sensitivity analysis, including a
closed-loop efficiency, are presented by means of numerical simulations. The
SCC-PS estimates simultaneously piston and tip-tilt misalignments and corrects
them in closed-loop operation. The SCC-PS does not require any a priori on the
signal at the segment boundaries or any dedicated optical path. It has a
moderate sensitivity to misalignments, virtually none to pupil shear, and is
insensitive to segment gaps and edge effects. Primary mirror phasing can be
achieved with bright natural guide star. The SCC-PS is a noninvasive concept
and an efficient phasing sensor from the image domain. It is an attractive
candidate for segment cophasing at the instrument level or alternatively at the
telescope level, as usually envisioned in current space- and ground-based
observatories.Comment: 10 pages. 9 figures. Accepted for publication in Astronomy &
Astrophysic
Furdenheim â Lotissement Altenweg, route de Quatzenheim
Ă Furdenheim, une fouille en milieu rural portant sur 8 073 m2 dâun projet de lotissement de 43 651 m2 (maĂźtrise dâouvrage du CM-CIC AmĂ©nagement foncier) a permis la dĂ©couverte dâun site dâhabitat prĂ©sentant deux phases dâoccupation. Lâemprise de ce projet dâamĂ©nagement se situe sur la parcelle qui fait face au complexe judo-basket dont la construction avait dĂ©jĂ permis la dĂ©couverte, en 2013, de deux petits secteurs dâhabitat de type ferme isolĂ©e, lâun du Bronze final (deux fosses et un dĂ©pĂŽ..
Stutzheim-Offenheim â A355, contournement ouest de Strasbourg (tronçon 3)
LâopĂ©ration de diagnostic du tronçon 3 du contournement ouest de Strasbourg sur les communes dâAchenheim, Ittenheim, Hurtigheim et Stutzheim-Offenheim a permis de documenter, sur une superficie de 81,47 ha, plusieurs occupations nĂ©olithiques, protohistoriques, gallo-romaines et contribuĂ© Ă approfondir notre connaissance des paysages anciens et de lâoccupation humaine dans ce secteur du Kochersberg pour ces pĂ©riodes holocĂšnes. La rĂ©alisation de sondages profonds dans les zones du projet en exc..
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