Littérature scientifique sur le sujet « Protoplanetary disks, planet formation, radio interferometry »
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Articles de revues sur le sujet "Protoplanetary disks, planet formation, radio interferometry"
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Andrews, Sean M. « Radio Interferometry Observations of the Hallmarks of Planet Formation ». Proceedings of the International Astronomical Union 8, S299 (juin 2013) : 80–89. http://dx.doi.org/10.1017/s1743921313007977.
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AbstractSome of the fundamental processes involved in the evolution of circumstellar disks and the assembly of planetary systems are just now becoming accessible to astronomical observations. The new promise of observational work in the field of planet formation makes for a very dynamic research scenario, which is certain to be amplified in the coming years as the revolutionary Atacama Large Millimeter/submillimeter Array (ALMA) facility ramps up to full operations. To highlight the new directions being explored in these fields, this brief review will describe how high angular resolution measurements at millimeter/radio wavelengths are being used to study several crucial aspects of the formation and early evolution of planetary systems, including: the gas and dust structures of protoplanetary disks, the growth and migration of disk solids, and the interactions between a young planetary system and its natal, gas-rich disk.
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Anthonioz, Fabien, F. Ménard, C. Pinte, W.-F. Thi, J. B. Lebouquin, J. P. Berger, M. Benisty et al. « The VLTi/PIONIER survey of southern TTauri disks ». Proceedings of the International Astronomical Union 8, S299 (juin 2013) : 94–98. http://dx.doi.org/10.1017/s1743921313007990.
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AbstractStudying the inner regions of protoplanetary disks (1-10 AU) is of importance to understand the formation of planets and the accretion process feeding the forming central star. Herbig AeBe stars are bright enough to be routinely observed by Near IR interferometers. The data for the fainter T Tauri stars is much more sparse. In this contribution we present the results of our ongoing survey at the VLTI. We used the PIONIER combiner that allows the simultaneous use of 4 telescopes, yielding 6 baselines and 3 independent closure phases at once. PIONIER's integrated optics technology makes it a sensitive instrument. We have observed 22 T Tauri stars so far, the largest survey for T Tauri stars to this date.Our results demonstrate the very significant contribution of an extended component to the interferometric signal. The extended component is different from source to source and the data, with several baselines, offer a way to improve our knowledge of the disk geometry and/or composition. These results validate an earlier study by Pinte et al. 2008 and show that the dust inner radii of T Tauri disks now appear to be in better agreement with the expected position of the dust sublimation radius, contrary to previous claims.
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Kraus, Adam L., et Michael J. Ireland. « The Role of Multiplicity in Protoplanetary Disk Evolution ». Proceedings of the International Astronomical Union 5, H15 (novembre 2009) : 766. http://dx.doi.org/10.1017/s174392131001149x.
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AbstractInteractions with close stellar or planetary companions can significantly influence the evolution and lifetime of protoplanetary disks. It has recently become possible to search for these companions, directly studying the role of multiplicity in protoplanetary disk evolution. We have described an ongoing survey to directly detect these stellar and planetary companions in nearby star-forming regions. Our program uses adaptive optics and sparse aperture mask interferometry to achieve typical contrast limits of Δ K=5-6 at the diffraction limit (5–8 MJup at 5–30 AU), while also detecting similar-flux binary companions at separations as low as 15 mas (2.5 AU). In most cases, our survey has found no evidence of companions (planetary or binary) among the well-known “transitional disk” systems; if the inner clearings are due to planet formation, as has been previously suggested, then this paucity places an upper limit on the mass of any resulting planet. Our survey also has uncovered many new binary systems, with the majority falling among the diskless (WTTS) population. This disparity suggests that disk evolution for close (5–30 AU) binary systems is very different from that for single stars. As we show in Figure 1, most circumbinary disks are cleared by ages of 1–2 Myr, while most circumstellar disks are not. These diskless binary systems have biased the disk frequency downward in previous studies. If we remove our new systems from those samples, we find that the disk fraction for single stars could be higher than was previously suggested.
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Brown, Joanna M. « SpS1-Dust and gas clearing in transitional disks ». Proceedings of the International Astronomical Union 5, H15 (novembre 2009) : 521. http://dx.doi.org/10.1017/s1743921310010483.
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Understanding how disks dissipate is essential to studies of planet formation. Infrared observations of young stars demonstrate that optically-thick circumstellar disks disappear from around half the stars in low-mass star-forming regions by an age of 3 Myr and are almost entirely absent in 10 Myr old associations (e.g. Haisch et al., 2001). Accretion ceases on the same approximate timescale (e.g. Calvet et al. 2005). The disappearence of gas and dust - planetary building material - places stringent limits on the timescales of giant planet formation. During this crucial interval, planet(esimal)s form and the remaining disk material is accreted or dispersed. Mid-infrared spectrophotometry of protoplanetary disks has revealed a small sub-class of objects in the midst of losing their disk material. These disks have spectral energy distributions (SEDs) suggestive of large inner gaps with low dust content, often interpreted as a signature of young planets. Such objects are still rare although Spitzer surveys have significantly increased the number of known transitional objects (e.g. Brown et al. 2007, D'Alessio et al., 2005). However, spectrophotometric signatures are indirect and notoriously difficult to interpret as multiple physical scenarios can result in the same SED. Recent direct imaging from millimeter interferometry has confirmed the presence of large inner holes in transitional disks, providing additional constraints and lending confidence to current SED interpretations (Brown et al. 2008, Brown et al. 2009, Andrews et al. 2009, Isella et al., 2009).
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Xin, Z., C. C. Espaillat, A. M. Rilinger, Á. Ribas et E. Macías. « Measuring the Dust Masses of Protoplanetary Disks in Lupus with ALMA : Evidence That Disks Can Be Optically Thick at 3 mm ». Astrophysical Journal 942, no 1 (28 décembre 2022) : 4. http://dx.doi.org/10.3847/1538-4357/aca52b.
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Abstract Accurate disk mass measurements are necessary to constrain disk evolution and the timescale of planet formation, but such measurements are difficult to make and are very dependent on assumptions. Here, we look at the assumption that the disk is optically thin at radio wavelengths and the effect of this assumption on measurements of disk dust mass. We model the optical to radio spectral energy distributions of 41 protoplanetary disks located in the young (∼1–3 Myr old) Lupus star-forming region, including 0.89 1.33 and 3 mm flux densities when available. We measure disk dust masses that are ∼1.5–6 times higher than when using the commonly adopted disk dust mass equation under the assumption of optically thin emission in the (sub)millimeter range. The cause of this discrepancy is that most disks are optically thick at millimeter wavelengths, even up to 3 mm, demonstrating that observations at longer wavelengths are needed to trace the fully optically thin emission of disks.
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Brunngräber, Robert, et Sebastian Wolf. « Constraints on observing brightness asymmetries in protoplanetary disks at solar system scale ». Astronomy & ; Astrophysics 611 (mars 2018) : A90. http://dx.doi.org/10.1051/0004-6361/201731907.
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We have quantified the potential capabilities of detecting local brightness asymmetries in circumstellar disks with the Very Large Telescope Interferometer (VLTI) in the mid-infrared wavelength range. The study is motivated by the need to evaluate theoretical models of planet formation by direct observations of protoplanets at early evolutionary stages, when they are still embedded in their host disk. Up to now, only a few embedded candidate protoplanets have been detected with semi-major axes of 20–50 au. Due to the small angular separation from their central star, only long-baseline interferometry provides the angular resolving power to detect disk asymmetries associated to protoplanets at solar system scales in nearby star-forming regions. In particular, infrared observations are crucial to observe scattered stellar radiation and thermal re-emission in the vicinity of embedded companions directly. For this purpose we performed radiative transfer simulations to calculate the thermal re-emission and scattered stellar flux from a protoplanetary disk hosting an embedded companion. Based on that, visibilities and closure phases are calculated to simulate observations with the future beam combiner MATISSE, operating at the L, M and N bands at the VLTI. We find that the flux ratio of the embedded source to the central star can be as low as 0.5 to 0.6% for a detection at a feasible significance level due to the heated dust in the vicinity of the embedded source. Furthermore, we find that the likelihood for detection is highest for sources at intermediate distances r ≈ 2–5 au and disk masses not higher than ≈10−4 M⊙.
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Lee, Eve J., J. R. Fuentes et Philip F. Hopkins. « Establishing Dust Rings and Forming Planets within Them ». Astrophysical Journal 937, no 2 (1 octobre 2022) : 95. http://dx.doi.org/10.3847/1538-4357/ac8cfe.
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Abstract Radio images of protoplanetary disks demonstrate that dust grains tend to organize themselves into rings. These rings may be a consequence of dust trapping within gas pressure maxima, wherein the local high dust-to-gas ratio is expected to trigger the formation of planetesimals and eventually planets. We revisit the behavior of dust near gas pressure perturbations enforced by a planet in two-dimensional, shearing-box simulations. While dust grains collect into generally long-lived rings, particles with a small Stokes parameter τ s < 0.1 tend to advect out of the ring within a few drift timescales. Scaled to the properties of ALMA disks, we find that rings composed of larger particles (τ s ≥ 0.1) can nucleate a dust clump massive enough to trigger pebble accretion, which proceeds to ingest the entire dust ring well within ∼1 Myr. To ensure the survival of the dust rings, we favor a nonplanetary origin and typical grain size τ s ≲ 0.05–0.1. Planet-driven rings may still be possible but if so we would expect the orbital distance of the dust rings to be larger for older systems.
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Mesa, D., C. Ginski, R. Gratton, S. Ertel, K. Wagner, M. Bonavita, D. Fedele et al. « Signs of late infall and possible planet formation around DR Tau using VLT/SPHERE and LBTI/LMIRCam ». Astronomy & ; Astrophysics 658 (février 2022) : A63. http://dx.doi.org/10.1051/0004-6361/202142219.
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Context. Protoplanetary disks around young stars often contain substructures like rings, gaps, and spirals that could be caused by interactions between the disk and forming planets. Aims. We aim to study the young (1–3 Myr) star DR Tau in the near-infrared and characterize its disk, which was previously resolved through submillimeter interferometry with ALMA, and to search for possible substellar companions embedded into it. Methods. We observed DR Tau with VLT/SPHERE both in polarized light (H broad band) and total intensity (in Y, J, H, and K spectral bands). We also performed L′ band observations with LBTI/LMIRCam on the Large Binocular Telescope (LBT). We applied differential imaging techniques to analyze both the polarized data, using dual beam polarization imaging, and the total intensity data, using angular and spectral differential imaging. Results. We found two previously undetected spirals extending north-east and south of the star, respectively. We further detected an arc-like structure north of the star. Finally a bright, compact and elongated structure was detected at a separation of 303 ± 10 mas and a position angle 21.2 ± 3.7 degrees, just at the root of the north-east spiral arm. Since this feature is visible both in polarized light and total intensity and has a blue spectrum, itis likely caused by stellar light scattered by dust. Conclusions. The two spiral arms are at different separations from the star, have very different pitch angles, and are separated by an apparent discontinuity, suggesting they might have a different origin. The very open southern spiral arm might be caused by infalling material from late encounters with cloudlets into the formation environment of the star itself. The compact feature could be caused by interaction with a planet in formation still embedded in its dust envelope and it could be responsible for launching the north–east spiral. We estimate a mass of the putative embedded object of the order of few MJup.
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Kluska, J., J. P. Berger, F. Malbet, B. Lazareff, M. Benisty, J. B. Le Bouquin, O. Absil et al. « A family portrait of disk inner rims around Herbig Ae/Be stars ». Astronomy & ; Astrophysics 636 (avril 2020) : A116. http://dx.doi.org/10.1051/0004-6361/201833774.
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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 ~30% of the objects (5/15) and noncentrosymmetric morphology due to a nonaxisymmetric and possibly variable environment (4/15, ~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.
Thèses sur le sujet "Protoplanetary disks, planet formation, radio interferometry"
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Sallum, Stephanie Elise, et Stephanie Elise Sallum. « Imaging Planet Formation Inside the Diffraction Limit ». Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625645.
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For decades, astronomers have used observations of mature planetary systems to constrain planet formation theories, beginning with our own solar system and now the thousands of known exoplanets. Recent advances in instrumentation have given us a direct view of some steps in the planet formation process, such as large-scale protostar and protoplanetary disk features and evolution. However, understanding the details of how planets accrete and interact with their environment requires direct observations of protoplanets themselves. Transition disks, protoplanetary disks with inner clearings that may be caused by forming planets, are the best targets for these studies. Their large distances, compared to the stars normally targeted for direct imaging of exoplanets, make protoplanet detection difficult and necessitate novel imaging techniques.
In this dissertation, I describe the results of using non-redundant masking (NRM) to search for forming planets in transition disk clearings. I first present a data reduction pipeline that I wrote to this end, using example datasets and simulations to demonstrate reduction and imaging optimizations. I discuss two transition disk NRM case studies: T Cha and LkCa 15. In the case of T Cha, while we detect significant asymmetries, the data cannot be explained by orbiting companions. The fluxes and orbital motion of the LkCa 15 companion signals, however, can be naturally explained by protoplanets in the disk clearing. I use these datasets and simulated observations to illustrate the effects of scattered light from transition disk material on NRM protoplanet searches. I then demonstrate the utility of the dual-aperture Large Binocular Telescope Interferometer's NRM mode on the bright B[e] star MWC 349A. I discuss the implications of this work for planet formation studies as well as future prospects for NRM and related techniques on next generation instruments.
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Kraus, Stefan, John D. Monnier, Michael J. Ireland, Gaspard Duchêne, Catherine Espaillat, Sebastian Hönig, Attila Juhasz et al. « Planet Formation Imager (PFI) : science vision and key requirements ». SPIE-INT SOC OPTICAL ENGINEERING, 2016. http://hdl.handle.net/10150/622530.
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The Planet Formation Imager (PFI) project aims to provide a strong scientific vision for ground-based optical astronomy beyond the upcoming generation of Extremely Large Telescopes. We make the case that a breakthrough in angular resolution imaging capabilities is required in order to unravel the processes involved in planet formation. PFI will be optimised to provide a complete census of the protoplanet population at all stellocentric radii and over the age range from 0.1 to similar to 100 Myr. Within this age period, planetary systems undergo dramatic changes and the final architecture of planetary systems is determined. Our goal is to study the planetary birth on the natural spatial scale where the material is assembled, which is the "Hill Sphere" of the forming planet, and to characterise the protoplanetary cores by measuring their masses and physical properties. Our science working group has investigated the observational characteristics of these young protoplanets as well as the migration mechanisms that might alter the system architecture. We simulated the imprints that the planets leave in the disk and study how PFI could revolutionise areas ranging from exoplanet to extragalactic science. In this contribution we outline the key science drivers of PFI and discuss the requirements that will guide the technology choices, the site selection, and potential science/technology tradeoffs.
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GUIDI, GRETA. « From dust to planets : high resolution observations of small-scale structures in evolving protoplanetary disks ». Doctoral thesis, 2018. http://hdl.handle.net/2158/1120851.
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This thesis work aimed at studying the first stages planet formation, focusing on protoplanetary disks of gas and dust around pre-main sequence stars. During their relatively short life (≥ 5 Million years) disks are expected to give origin to large solid bodies and planets, but the mechanisms and timescales of these process are still not well constrained. In particular, the so called "core accretion" scenario predicts that dust grains stick together via direct collisions and form larger aggregates up to planetesimals sizes; but both simulations and laboratory experiments show that grain growth should be hindered by two main mechanisms, the first leading to destructive outcomes when grains collide beyond a certain size/velocity ("fragmentation barrier"), the second removing bigger grains as a consequence of the aerodynamical drag that the gas exerts on the dust ("drift barrier"). The fact that we observe large grains in several protoplanetary disks, and the evidence of a large number of extrasolar planetary systems, suggest that there must be other mechanisms that promote grain growth, overcoming these two main barriers. In this framework I focused on studying disk evolution through high resolution observations taken with new-generation radio intreferometers, with the purpose of obtaining a better understanding of the mechanisms driving dust growth and ultimately planet formation.