192 research outputs found
A survey of comics research in computer science
Graphical novels such as comics and mangas are well known all over the world.
The digital transition started to change the way people are reading comics,
more and more on smartphones and tablets and less and less on paper. In the
recent years, a wide variety of research about comics has been proposed and
might change the way comics are created, distributed and read in future years.
Early work focuses on low level document image analysis: indeed comic books are
complex, they contains text, drawings, balloon, panels, onomatopoeia, etc.
Different fields of computer science covered research about user interaction
and content generation such as multimedia, artificial intelligence,
human-computer interaction, etc. with different sets of values. We propose in
this paper to review the previous research about comics in computer science, to
state what have been done and to give some insights about the main outlooks
The twofold debris disk around HD 113766 A - Warm and cold dust as seen with VLTI/Midi and Herschel/Pacs
Warm debris disks are a sub-sample of the large population of debris disks,
and display excess emission in the mid-IR. Around solar-type stars, very few
objects show emission features in mid-IR spectroscopic observations, that are
attributed to small, warm silicate dust grains. The origin of this warm dust
can possibly be explained either by a collision between several bodies or by
transport from an outer belt. We present and analyse new far-IR Herschel/Pacs
observations, supplemented by ground-based data in the mid-IR (VLTI/Midi and
VLT/Visir), for one of these rare systems: the 10-16 Myr old debris disk around
HD 113766 A. We improve an existing model to account for these new
observations, and better constrain the spatial distribution of the dust and its
composition. We underline the limitations of SED modelling and the need for
spatially resolved observations. We find that the system is best described by
an inner disk located within the first AU, well constrained by the Midi data,
and an outer disk located between 9-13 AU. In the inner dust belt, our previous
finding of Fe-rich crystalline olivine grains still holds. We do not observe
time variability of the emission features over at least a 8 years time span, in
a environment subjected to strong radiation pressure. The time stability of the
emission features indicates that {\mu}m-sized dust grains are constantly
replenished from the same reservoir, with a possible depletion of
sub-{\mu}m-sized grains. We suggest that the emission features may arise from
multi-composition aggregates. We discuss possible scenarios concerning the
origin of the warm dust. The compactness of the innermost regions as probed by
Midi, as well as the dust composition, suggest that we are witnessing the
outcomes of (at least) one collision between partially differentiated bodies,
in an environment possibly rendered unstable by terrestrial planetary
formation
Searching for faint companions with VLTI/PIONIER. II. 92 main sequence stars from the Exozodi survey
The Exozodi survey aims to determine the occurrence rate of bright
exozodiacal discs around nearby main sequence stars using infrared
interferometry. Although the Exozodi survey targets have been carefully
selected to avoid the presence of binary stars, the results of this survey can
still be biased by the presence of unidentified stellar companions. Using the
PIONIER data set collected within the Exozodi survey, we aim to search for the
signature of point-like companions around the Exozodi target stars. We use both
the closure phases and squared visibilities collected by PIONIER to search for
companions within the ~100 mas interferometric field of view. The presence of a
companion is assessed by computing the goodness of fit to the data for a series
of binary models with various separations and contrasts. Five stellar
companions are resolved for the first time around five A-type stars: HD 4150,
HD 16555, HD 29388, HD 202730, and HD 224392 (although the companion to HD
16555 was independently resolved by speckle interferometry while we were
carrying out the survey). In the most likely case of main sequence companions,
their spectral types range from A5V to K4V. Three of these stars were already
suspected to be binaries from Hipparcos astrometric measurements, although no
information was available on the companions themselves so far. In addition to
debiasing the statistics of the Exozodi survey, these results can also be used
to revise the fraction of visual binaries among A-type stars, suggesting that
an extra ~13% A-type stars are visual binaries in addition to the ones detected
in previous direct imaging surveys. We estimate that about half the population
of nearby A-type stars could be resolved as visual binaries using a combination
of state-of-the-art interferometry and single-aperture imaging, and we suggest
that a significant fraction of these binaries remains undetected to date.Comment: Accepted for publication in A&
A near-infrared interferometric survey of debris-disc stars. IV. An unbiased sample of 92 southern stars observed in H-band with VLTI/PIONIER
Context. Detecting and characterizing circumstellar dust is a way to study
the architecture and evolution of planetary systems. Cold dust in debris disks
only traces the outer regions. Warm and hot exozodiacal dust needs to be
studied in order to trace regions close to the habitable zone.
Aims. We aim to determine the prevalence and to constrain the properties of
hot exozodiacal dust around nearby main-sequence stars.
Methods. We search a magnitude limited (H < 5) sample of 92 stars for bright
exozodiacal dust using our VLTI visitor instrument PIONIER in the H-band. We
derive statistics of the detection rate with respect to parameters such as the
stellar spectral type and age or the presence of a debris disk in the outer
regions of the systems. We derive more robust statistics by combining our
sample with the results from our CHARA/FLUOR survey in the K-band. In addition,
our spectrally dispersed data allows us to put constraints on the emission
mechanism and the dust properties in the detected systems.
Results. We find an over-all detection rate of bright exozodiacal dust in the
H-band of 11% (9 out of 85 targets) and three tentative detections. The
detection rate decreases from early type to late type stars and increases with
the age of the host star. We do not confirm the tentative correlation between
the presence of cold and hot dust found in our earlier analysis of the FLUOR
sample alone. Our spectrally dispersed data suggest that either the dust is
extremely hot or the emission is dominated by the scattered light in most
cases. The implications of our results for the target selection of future
terrestrial planet finding missions using direct imaging are discussed.Comment: 20 pages, 16 figures, 4 tables, updated references and minor changes
to the text, accepted for publication in A&
Diffusion géométrique pour le masquage d'erreurs de quantification et de transmission sur des images JPEG couleur
Nous proposons ici une méthode de masquage d'erreurs de transmission basée contenue. Contrairement aux schémas classiques de correction d'erreurs de type FEQ/ARQ, notre méthode ne nécessite pas l'ajout de données de contrôle, et exploite directement la redondance spatiale de l'image source. Elle consiste en effet à interpoler les zones valides de l'image reçue dans les zones corrompues, à l'aide d'un processus de diffusion sous contraintes géométriques couplé à une approche multi-résolution. Outre les erreurs de transmission, ce modèle de diffusion nous permet de masquer également les erreurs de quantification (artefacts de compression)
An Unbiased Near-infrared Interferometric Survey for Hot Exozodiacal Dust
Exozodiacal dust is warm or hot dust found in the inner regions of planetary
systems orbiting main sequence stars, in or around their habitable zones. The
dust can be the most luminous component of extrasolar planetary systems, but
predominantly emits in the near- to mid-infrared where it is outshone by the
host star. Interferometry provides a unique method of separating this dusty
emission from the stellar emission. The visitor instrument PIONIER at the Very
Large Telescope Interferometer (VLTI) has been used to search for hot
exozodiacal dust around a large sample of nearby main sequence stars. The
results of this survey are summarised: 9 out of 85 stars show excess
exozodiacal emission over the stellar photospheric emission.Comment: Invited review of our paper (Ertel et al., 2014) for ESO's The
Messenger, issue 159. Final version as published in The Messenge
An interferometric study of the Fomalhaut inner debris disk. I. Near-infrared detection of hot dust with VLTI/VINCI
The innermost parts of dusty debris disks around main sequence stars are
currently poorly known due to the high contrast and small angular separation
with their parent stars. Using near-infrared interferometry, we aim to detect
the signature of hot dust around the nearby A4 V star Fomalhaut, which has
already been suggested to harbor a warm dust population in addition to a cold
dust ring located at about 140 AU. Archival data obtained with the VINCI
instrument at the VLTI are used to study the fringe visibility of the Fomalhaut
system at projected baseline lengths ranging from 4 m to 140 m in the K band. A
significant visibility deficit is observed at short baselines with respect to
the expected visibility of the sole stellar photosphere. This is interpreted as
the signature of resolved circumstellar emission, producing a relative flux of
0.88% +/- 0.12% with respect to the stellar photosphere. While our
interferometric data cannot directly constrain the morphology of the excess
emission source, complementary data from the literature allow us to discard an
off-axis point-like object as the source of circumstellar emission. We argue
that the thermal emission from hot dusty grains located within 6 AU from
Fomalhaut is the most plausible explanation for the detected excess. Our study
also provides a revised limb-darkened diameter for Fomalhaut (2.223 +/- 0.022
mas), taking into account the effect of the resolved circumstellar emission.Comment: 13 pages, accepted for publication in Ap
Deep imaging of β Pictoris at L’: asymmetries in the disc and constraints on planets
We demonstrate here the potential of VLT/NaCo at
L’ (3.8μm) in Angular Differential Imaging (ADI). We detect
the β Pictoris disc above 5σ between 0.4’’ and 3.8’’, after
combining data from 7 epochs or 3.1 years. To avoid the
smearing of the planet due to its orbital motion within this
time span (green arrow), we subtracted the planet from the
7 datasets. We used a star subtraction technique based on
PCA (Soummer et al. 2012) and corrected for ADI biases by
iterating. We implemented a forward modeling approach to
constrain the dust distribution
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
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