Browsing by Author "Pohl, A."

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    Discovery of a planetary-mass companion within the gap of the transition disk around PDS 70
    (EDP Sciences, 2018) Keppler, M.; Benisty, M.; Müller, A.; Henning, Th.; van Boekel, R.; Cantalloube, F.; Ginski, C.; van Holstein, R.G.; Maire, A.-L.; Pohl, A.; Samland, M.; Avenhaus, H.; Baudino, J.-L.; Boccaletti, A.; de Boer, J.; Bonnefoy, M.; Chauvin, G.; Desidera, S.; Langlois, M.; Lazzoni, C.; Marleau, G.-D.; Mordasini, C.; Pawellek, N.; Stolker, T.; Vigan, A.; Zurlo, A.; Birnstiel, T.; Brandner, W.; Feldt, M.; Flock, M.; Girard, J.; Gratton, R.; Hagelberg, J.; Isella, A.; Janson, M.; Juhasz, A.; Kemmer, J.; Kral, Q.; Lagrange, A.-M.; Launhardt, R.; Matter, A.; Ménard, F.; Milli, J.; Mollière, P.; Olofsson, J.; Pérez, L.; Pinilla, P.; Pinte, C.; Quanz, S.P.; Schmidt, T.; Udry, S.; Wahhaj, Z.; Williams, J.P.; Buenzli, E.; Cudel, M.; Dominik, C.; Galicher, R.; Kasper, M.; Lannier, J.; Mesa, D.; Mouillet, D.; Peretti, S.; Perrot, C.; Salter, G.; Sissa, E.; Wildi, F.; Abe, L.; Antichi, J.; Augereau, J.-C.; Baruffolo, A.; Baudoz, P.; Bazzon, A.; Beuzit, J.-L.; Blanchard, P.; Brems, S.S.; Buey, T.; De Caprio, V.; Carbillet, M.; Carle, M.; Cascone, E.; Cheetham, A.; Claudi, R.; Costille, A.; Delboulbé, A.; Dohlen, K.; Fantinel, D.; Feautrier, P.; Fusco, T.; Giro, E.; Gluck, L.; Gry, C.; Hubin, N.; Hugot, E.; Jaquet, M.; Le Mignant, D.; Llored, M.; Madec, F.; Magnard, Y.; Martinez, P.; Maurel, D.; Meyer, M.; Möller-Nilsson, O.; Moulin, T.; Mugnier, L.; Origné, A.; Pavlov, A.; Perret, D.; Petit, C.; Pragt, J.; Puget, P.; Rabou, P.; Ramos, J.; Rigal, F.; Rochat, S.; Roelfsema, R.; Rousset, G.; Roux, A.; Salasnich, B.; Sauvage, J.-F.; Sevin, A.; Soenke, C.; Stadler, E.; Suarez, M.; Turatto, M.; Weber, L.
    Context. Young circumstellar disks are the birthplaces of planets. Their study is of prime interest to understand the physical and chemical conditions under which planet formation takes place. Only very few detections of planet candidates within these disks exist, and most of them are currently suspected to be disk features. Aims. In this context, the transition disk around the young star PDS 70 is of particular interest, due to its large gap identified in previous observations, indicative of ongoing planet formation. We aim to search for the presence of an embedded young planet and search for disk structures that may be the result of disk–planet interactions and other evolutionary processes. Methods. We analyse new and archival near-infrared images of the transition disk PDS 70 obtained with the VLT/SPHERE, VLT/NaCo, and Gemini/NICI instruments in polarimetric differential imaging and angular differential imaging modes. Results. We detect a point source within the gap of the disk at about 195 mas (~22 au) projected separation. The detection is confirmed at five different epochs, in three filter bands and using different instruments. The astrometry results in an object of bound nature, with high significance. The comparison of the measured magnitudes and colours to evolutionary tracks suggests that the detection is a companion of planetary mass. The luminosity of the detected object is consistent with that of an L-type dwarf, but its IR colours are redder, possibly indicating the presence of warm surrounding material. Further, we confirm the detection of a large gap of ~54 au in size within the disk in our scattered light images, and detect a signal from an inner disk component. We find that its spatial extent is very likely smaller than ~17 au in radius, and its position angle is consistent with that of the outer disk. The images of the outer disk show evidence of a complex azimuthal brightness distribution which is different at different wavelengths and may in part be explained by Rayleigh scattering from very small grains. Conclusions. The detection of a young protoplanet within the gap of the transition disk around PDS 70 opens the door to a so far observationally unexplored parameter space of planetary formation and evolution. Future observations of this system at different wavelengths and continuing astrometry will allow us to test theoretical predictions regarding planet–disk interactions, planetary atmospheres, and evolutionary models.
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    Dust modeling of the combined ALMA and SPHERE datasets of HD 163296. Is HD 163296 really a Meeus group II disk?
    (EDP Sciences, 2018) Muro-Arena, G.A.; Dominik, C.; Waters, L.B.F.M.; Min, M.; Klarmann, L.; Ginski, C.; Isella, A.; Benisty, M.; Pohl, A.; Garufi, A.; Hagelberg, J.; Langlois, M.; Menard, F.; Pinte, C.; Sezestre, E.; van der Plas, G.; Villenave, M.; Delboulbé, A.; Magnard, Y.; Möller-Nilsson, O.; Pragt, J.; Rabou, P.; Roelfsema, R.
    Context. Multiwavelength observations are indispensable in studying disk geometry and dust evolution processes in protoplanetary disks. Aims. We aim to construct a three-dimensional model of HD 163296 that is capable of reproducing simultaneously new observations of the disk surface in scattered light with the SPHERE instrument and thermal emission continuum observations of the disk midplane with ALMA. We want to determine why the spectral energy distribution of HD 163296 is intermediary between the otherwise well-separated group I and group II Herbig stars. Methods. The disk was modeled using the Monte Carlo radiative transfer code MCMax3D. The radial dust surface density profile was modeled after the ALMA observations, while the polarized scattered light observations were used to constrain the inclination of the inner disk component and turbulence and grain growth in the outer disk. Results. While three rings are observed in the disk midplane in millimeter thermal emission at ~80, 124, and 200 AU, only the innermost of these is observed in polarized scattered light, indicating a lack of small dust grains on the surface of the outer disk. We provide two models that are capable of explaining this difference. The first model uses increased settling in the outer disk as a mechanism to bring the small dust grains on the surface of the disk closer to the midplane and into the shadow cast by the first ring. The second model uses depletion of the smallest dust grains in the outer disk as a mechanism for decreasing the optical depth at optical and near-infrared wavelengths. In the region outside the fragmentation-dominated regime, such depletion is expected from state-of-the-art dust evolution models. We studied the effect of creating an artificial inner cavity in our models, and conclude that HD 163296 might be a precursor to typical group I sources.