Suchergebnisse

High dust density in the midplane of protoplanetary disks is favorable for efficient grain growth and can allow fast formation of planetesimals and planets, before disks dissipate. Vertical settling and dust trapping in pressure maxima are two mechanisms allowing dust to concentrate in geometrically thin and high-density regions. In this work, we aim to study these mechanisms in the highly inclined protoplanetary disk SSTC2D J163131.2-242627 (Oph 163131, i similar to 84 degrees). We present new high-angular-resolution continuum and (CO)-C-12 ALMA observations of Oph 163131. The gas emission appears significantly more extended in the vertical and radial direction compared to the dust emission, consistent with vertical settling and possibly radial drift. In addition, the new continuum observations reveal two clear rings. The outer ring, located at similar to 100 au, is well-resolved in the observations, allowing us to put stringent constraints on the vertical extent of millimeter dust particles. We model the disk using radiative transfer and find that the scale height of millimeter-sized grains is 0.5 au or less at 100 au from the central star. This value is about one order of magnitude smaller than the scale height of smaller micron-sized dust grains constrained by previous modeling, which implies that efficient settling of the large grains is occurring in the disk. When adopting a parametric dust settling prescription, we find that the observations are consistent with a turbulent viscosity coefficient of about alpha less than or similar to 10(-5) at 100 au. Finally, we find that the thin dust scale height measured in Oph 163131 is favorable for planetary growth by pebble accretion: a 10 M (E) planet may grow within less than 10 Myr, even in orbits exceeding 50 au. ; National Aeronautics & Space Administration (NASA) European Union's Horizon 2020 research and innovation program under the Marie Skodowska-Curie grant 210021 National Aeronautics & Space Administration (NASA) NNX15AC89G NNX15AD95G/NExSS ...

Context. Shadows in scattered light images of protoplanetary disks are a common feature and support the presence of warps or misalignments between disk regions. These warps are possibly caused by an inclined (sub-)stellar companion embedded in the disk. Aims. We aim to study the morphology of the protoplanetary disk around the Herbig Ae star HD 139614 based on the first scattered light observations of this disk, which we model with the radiative transfer code MCMax3D. Methods. We obtained J- and H-band observations that show strong azimuthal asymmetries in polarized scattered light with VLT/SPHERE. In the outer disk, beyond similar to 30 au, a broad shadow spans a range of similar to 240 deg in position angle, in the east. A bright ring at similar to 16 au also shows an azimuthally asymmetric brightness, with the faintest side roughly coincidental with the brightest region of the outer disk. Additionally, two arcs are detected at similar to 34 and similar to 50 au. We created a simple four-zone approximation to a warped disk model of HD 139614 in order to qualitatively reproduce these features. The location and misalignment of the disk components were constrained from the shape and location of the shadows they cast. Results. We find that the shadow on the outer disk covers a range of position angles too wide to be explained by a single inner misaligned component. Our model requires a minimum of two separate misaligned zones - or a continuously warped region - to cast this broad shadow on the outer disk. A small misalignment of similar to 4 degrees between adjacent components can reproduce most of the observed shadow features. Conclusions. Multiple misaligned disk zones, potentially mimicking a warp, can explain the observed broad shadows in the HD 139614 disk. A planetary mass companion in the disk, located on an inclined orbit, could be responsible for such a feature and for the dust-depleted gap responsible for a dip in the SED. ; SO Centre National de la Recherche Scientifique (CNRS) MPIA (Germany) Istituto Nazionale Astrofisica (INAF) FINES (Switzerland) NOVA (The Netherlands) European Union (EU) RII3Ct2004-001566 European Union (EU) 226604 312430 Netherlands Organisation for Scientific Research (NWO) TOP-1 grant as part of the research program "Herbig Ae/Be stars, Rosetta stones for understanding the formation of planetary systems" 614.001.552 French National Research Agency (ANR) ANR16-CE31-0013 CONICYT + PAI/Convocatoria nacional subvencion a la instalacion en la academia, convocatoria 2017 + Folio PAI77170087

Context. The innermost astronomical unit (au) in protoplanetary disks is a key region for stellar and planet formation, as exoplanet searches have shown a large occurrence of close-in planets that are located within the first au around their host star. Aims. We aim to reveal the morphology of the disk inner rim using near-infrared interferometric observations with milli-arcsecond resolution provided by near-infrared multitelescope interferometry. Methods. We provide model-independent reconstructed images of 15 objects selected from the Herbig AeBe survey carried out with PIONIER at the Very Large Telescope Interferometer, using the semi-parametric approach for image reconstruction of chromatic objects. We propose a set of methods to reconstruct and analyze the images in a consistent way. Results. We find that 40% of the systems (6/15) are centrosymmetric at the angular resolution of the observations. For the rest of the objects, we find evidence for asymmetric emission due to moderate-to-strong inclination of a disk-like structure for similar to 30% of the objects (5/15) and noncentrosymmetric morphology due to a nonaxisymmetric and possibly variable environment (4/15, similar to 27%). Among the systems with a disk-like structure, 20% (3/15) show a resolved dust-free cavity. Finally, we do not detect extended emission beyond the inner rim. Conclusions. The image reconstruction process is a powerful tool to reveal complex disk inner rim morphologies, which is complementary to the fit of geometrical models. At the angular resolution reached by near-infrared interferometric observations, most of the images are compatible with a centrally peaked emission (no cavity). For the most resolved targets, image reconstruction reveals morphologies that cannot be reproduced by generic parametric models (e.g., perturbed inner rims or complex brightness distributions). Moreover, the nonaxisymmetric disks show that the spatial resolution probed by optical interferometers makes the observations of the near-infrared emission (inside a few au) sensitive to temporal evolution with a time-scale down to a few weeks. The evidence of nonaxisymmetric emission that cannot be explained by simple inclination and radiative transfer effects requires alternative explanations, such as a warping of the inner disks. Interferometric observations can therefore be used to follow the evolution of the asymmetry of those disks at an au or sub-au scale. ; French National Research Agency (ANR) ANR-10-BLAN-0511 European Union (EU) SH-06192 Philip Leverhulme Prize PLP-2013-110 KU Leuven C14/17/082 National Science Foundation (NSF) 1210972 1616483 European Research Council (ERC) 639889 European Union (EU) 284405 French National Research Agency (ANR) ANR-16-CE31-0013 Australian Research Council FT170100040 DP180104235 Universite Joseph Fourier (UJF, Grenoble) through its Pole TUNES Universite Joseph Fourier (UJF, Grenoble) through its Pole SMING Institut de Planetologie et d'Astrophysique de Grenoble French National Research Agency (ANR) French National Research Agency (ANR) Institut National des Science de l'Univers (INSU) via the "Programme National de Physique Stellaire" Institut National des Science de l'Univers (INSU) via "Programme National de Planetologie"

Context. A large portion of stars is found to be part of binary or higher-order multiple systems. The ubiquity of planets found around single stars raises the question of whether and how planets in binary systems form. Protoplanetary disks are the birthplaces of planets, and characterizing them is crucial in order to understand the planet formation process. Aims. Our goal is to characterize the morphology of the GG Tau A disk, one of the largest and most massive circumbinary disks. We also aim to trace evidence for binary-disk interactions. Methods. We obtained observations in polarized scattered light of GG Tau A using the SPHERE/IRDIS instrument in the H-band filter. We analyzed the observed disk morphology and substructures. We ran 2D hydrodynamical models to simulate the evolution of the circumbinary ring over the lifetime of the disk. Results. The disk and also the cavity and the inner region are highly structured, with several shadowed regions, spiral structures, and streamer-like filaments. Some of these are detected here for the first time. The streamer-like filaments appear to connect the outer ring with the northern arc. Their azimuthal spacing suggests that they may be generated through periodic perturbations by the binary, which tear off material from the inner edge of the outer disk once during each orbit. By comparing observations to hydrodynamical simulations, we find that the main features, in particular, the gap size, but also the spiral and streamer filaments, can be qualitatively explained by the gravitational interactions of a binary with a semimajor axis of similar to 35 au on an orbit coplanar with the circumbinary ring. ; European Research Council under the Horizon 2020 Framework Program via the ERC Advanced Grant Origins 83 24 28 French National Research Agency (ANR) ANR-16-CE31-0013 Australian Research Council FT170100040 DP180104235 European Union's Horizon 2020 research and innovation programme under the Marie Skodowska-Curie grant 823823 Comisión Nacional de Investigación Científica y Tecnológica (CONICYT) CONICYT FONDECYT 11190837 ESO Centre National de la Recherche Scientifique (CNRS) MPIA (Germany) Istituto Nazionale Astrofisica (INAF) FINES (Switzerland) NOVA (The Netherlands) European Union (EU) RII3-Ct2004-001566 European Union (EU) 226604 312430