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1. Revealing asymmetrical dust distribution in the inner regions of HD 141569

Author

Singh, Garima, Bhowmik, Trisha, Boccaletti, Anthony, Thébault, Philippe, Kral, Quentin, Milli, Julien, Mazoyer, Johan, Pantin, Eric, Olofsson, Johan, Boukrouche, Ryan, Di Folco, Emmanuel, Janson, Markus, Langlois, Maud, Maire, Anne Lise, Vigan, Arthur, Benisty, Myriam, Augereau, Jean-Charles, Perrot, Clement, Gratton, Raffaele, Henning, Thomas, Ménard, Francois, Rickman, Emily, Wahhaj, Zahed, Zurlo, Alice, Biller, Beth, Bonnefoy, Mickael, Chauvin, Gael, Delorme, Philippe, Desidera, Silvano, D'Orazi, Valentina, Feldt, Markus, Hagelberg, Janis, Keppler, Miriam, Kopytova, Taisiya, Lagadec, Eric, Lagrange, Anne-Marie, Mesa, Dino, Meyer, Michael, Rouan, Daniel, Sissa, Elena, Schmidt, Tobias, Jaquet, Marc, Fusco, Thierry, Pavlov, Alexei, and Rabou, Patrick

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

We obtained polarimetric differential imaging of a gas-rich debris disk around HD 141569A with SPHERE in the H-band to compare the scattering properties of the innermost ring at 44 au with former observations in total intensity with the same instrument. In polarimetric imaging, we observed that the intensity of the ring peaks in the south-east, mostly in the forward direction, whereas in total intensity imaging, the ring is detected only at the south. This noticeable characteristic suggests a non-uniform dust density in the ring. We implemented a density function varying azimuthally along the ring and generated synthetic images both in polarimetry and in total intensity, which are then compared to the actual data. We find that the dust density peaks in the south-west at an azimuthal angle of $220^{\circ} \sim 238^{\circ}$ with a rather broad width of $61^{\circ} \sim 127^{\circ}$. Although there are still uncertainties that remain in the determination of the anisotropic scattering factor, the implementation of an azimuthal density variation to fit the data proved to be robust. Upon elaborating on the origin of this dust density distribution, we conclude that it could be the result of a massive collision when we account for the effect of the high gas mass that is present in the system on the dynamics of grains. Using the outcome of this modelization, we further measured the polarized scattering phase function for the observed scattering angle between 33$^{\circ}$ and 147$^{\circ}$ as well as the spectral reflectance of the southern part of the ring between 0.98 $\mu$m and 2.1 $\mu$m. We tentatively derived the grain properties by comparing these quantities with MCFOST models and assuming Mie scattering. Our preliminary interpretation indicates a mixture of porous sub-micron sized astro-silicate and carbonaceous grains., Comment: 21 pages, 18 figures, Accepted for publication in Astronomy & Astrophysics journal

Published
2021
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2. First resolved observations of a highly asymmetric debris disc around HD 160305 with VLT/SPHERE

Author

Perrot, Clément, Thebault, Philippe, Lagrange, Anne-Marie, Boccaletti, Anthony, Vigan, Arthur, Desidera, Silvano, Augereau, Jean-Charles, Bonnefoy, Mickael, Choquet, Élodie, Kral, Quentin, Loh, Alan, Maire, Anne-Lise, Ménard, François, Messina, Sergio, Olofsson, Johan, Gratton, Raffaele, Biller, Beth, Brandner, Wolfgang, Buenzli, Esther, Chauvin, Gaël, Cheetham, Anthony, Daemgen, Sebastien, Delorme, Philippe, Feldt, Markus, Lagadec, Eric, Langlois, Maud, Lannier, Justine, Mesa, Dino, Mouillet, David, Peretti, Sébastien, Janin-Potiron, Pierre, Salter, Graeme, Sissa, Elena, Roux, Alain, Llored, Marc, Buey, Jean-Tristan, Pavlov, Alexei, Weber, Luc, and Petit, Cyril

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

Context. Direct imaging of debris discs gives important information about their nature, their global morphology, and allows us to identify specific structures possibly in connection with the presence of gravitational perturbers. It is the most straightforward technique to observe planetary systems as a whole. Aims. We present the first resolved images of the debris disc around the young F-type star HD 160305, detected in scattered light using the VLT/SPHERE instrument in the near infrared. Methods. We used a post-processing method based on angular differential imaging and synthetic images of debris discs produced with a disc modelling code (GRaTer) to constrain the main characteristics of the disc around HD 160305. All of the point sources in the field of the IRDIS camera were analysed with an astrometric tool to determine whether they are bound objects or background stars. Results. We detect a very inclined (~ 82{\deg}) ring-like debris disc located at a stellocentric distance of about 86au (deprojected width ~27 au). The disc displays a brightness asymmetry between the two sides of the major axis, as can be expected from scattering properties of dust grains. We derive an anisotropic scattering factor g>0.5. A second right-left asymmetry is also observed with respect to the minor axis. We measure a surface brightness ratio of 0.73 $\pm$ 0.18 between the bright and the faint sides. Because of the low signal-to-noise ratio (S/N) of the images we cannot easily discriminate between several possible explanations for this left-right asymmetry, such as perturbations by an unseen planet, the aftermath of the breakup of a massive planetesimal, or the pericenter glow effect due to an eccentric ring. Two epochs of observations allow us to reject the companionship hypothesis for the 15 point sources present in the field., Comment: 13 pages

Published
2019
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3. The SPHERE view of the planet-forming disk around HD100546

Author

Garufi, Antonio, Quanz, Sascha P., Schmid, Hans Martin, Mulders, Gijs D., Avenhaus, Henning, Boccaletti, Anthony, Ginski, Christian, Langlois, Maud, Stolker, Tomas, Augereau, Jean-Charles, Benisty, Myriam, Lopez, Bruno, Dominik, Carsten, Gratton, Raffaele, Henning, Thomas, Janson, Markus, Menard, Francois, Meyer, Michael R., Pinte, Christophe, Sissa, Elena, Vigan, Arthur, Zurlo, Alice, Bazzon, Andreas, Buenzli, Esther, Bonnefoy, Mickael, Brandner, Wolfgang, Chauvin, Gael, Cheetham, Anthony, Cudel, Maxime, Desidera, Silvano, Feldt, Markus, Galicher, Raphael, Kasper, Markus, Lagrange, Anne-Marie, Lannier, Justine, Maire, Anne-Lise, Mesa, Dino, Mouillet, David, Peretti, Sebastien, Perrot, Clement, Salter, Graeme, and Wildi, Francois

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

We image with unprecedented spatial resolution and sensitivity disk features that could be potential signs of planet-disk interaction. Two companion candidates have been claimed in the disk around the young Herbig Ae/Be star HD100546. Thus, this object serves as an excellent target for our investigation of the natal environment of giant planets. We exploit the power of extreme adaptive optics operating in conjunction with the new high-contrast imager SPHERE to image HD100546 in scattered light. We obtain the first polarized light observations of this source in the visible (with resolution as fine as 2 AU) and new H and K band total intensity images that we analyze with the Pynpoint package. The disk shows a complex azimuthal morphology, where multiple scattering of photons most likely plays an important role. High brightness contrasts and arm-like structures are ubiquitous in the disk. A double-wing structure (partly due to ADI processing) resembles a morphology newly observed in inclined disks. Given the cavity size in the visible (11 AU), the CO emission associated to the planet candidate 'c' might arise from within the circumstellar disk. We find an extended emission in the K band at the expected location of 'b'. The surrounding large-scale region is the brightest in scattered light. There is no sign of any disk gap associated to 'b'., Comment: Accepted by A&A. 13 pages, 5 figures

Published
2016
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4. The B-Star Exoplanet Abundance Study: a co-moving 16–25 M Jup companion to the young binary system HIP 79098

Author

Carbillet, M., Maurel, D., Origné, A., Rigal, F., Sevin, A., De Boer, J., van Holstein, R. G., Dohlen, K., Snik, F., Keller, C. U., Ginski, C., Stam, D. M., Wahhaj, Z., Kasper, M., Rabou, P., Hugot, E., Perret, D., Martinez, P., Pragt, J., Coroller, H. Le, Dominik, C., Turatto, M., Udry, S., Beuzit, J. -L., Le Coroller, H., Mennesson, B., Bailey, V., Kasdin, J., Trauger, J., Absil, O., Akeson, R., Armus, L., Baudoz, P., Bellini, A., Bennett, D., Berriman, B., Calchi-Novati, S., Carpenter, K., Chen, C., Danchi, W., Debes, J., Defrere, D., Ertel, S., Frerking, M., Gelino, C., Girard, J. H., Groff, T., Kane, S., Helou, G., Kalirai, J., Krist, J., Kruk, J., Hasegawa, Y., Laine, S., Lowrance, P., Malhotra, S., Mandell, A., Marshall, P., McElwain, M., Meshkat, T., Millan-Gabet, R., Moustakas, L., Nemati, B., Paladini, R., Postman, M., Pueyo, L., Quintana, E., Ramirez, S., Rhodes, J., Riggs, A. J. E., Rizzo, M., Soummer, R., Stapelfeldt, K., Stark, C., Turnbull, M., van der Marel, R., Ygouf, M., Wyatt, M., Zhao, F., Zimmerman, N., Loh, Alan, Messina, Sergio, Brandner, Wolfgang, Buenzli, Esther, Daemgen, Sebastien, Lagadec, Eric, Mouillet, David, Peretti, Sébastien, Janin-Potiron, Pierre, Salter, Graeme, Roux, Alain, Llored, Marc, Buey, Jean-Tristan, Pavlov, Alexei, Petit, C., Pawellek, Nicole, Moór, Attila, Milli, Julien, Kóspál, Ágnes, Olofsson, Johan, Ábrahám, Péter, Keppler, Miriam, Kral, Quentin, Pohl, Adriana, Augereau, Jean-Charles, Choquet, Elodie, Engler, Natalia, Lee, Eve J., Thebault, Philippe, Lee, Eve, Podio, L., Bacciotti, F., Antoniucci, S., Codella, C., Dougados, C., Nisini, B., Schmid, H. M., Stolker, T., Baudino, J. L., Biller, Beth, Bonavita, M., Galicher, R., Grandjean, A., Lagrange, Anne-Marie, Lannier, Justine, Maire, Anne-Lise, Perrot, Clément, Delboulbé, A., Mignant, D. Le, Fantinel, D., Moeller-Nilsson, O., Weber, Luc, Sauvage, J. -F., Le Mignant, D., Möller-Nilsson, O., Mesa, Dino, Garufi, A., D'Orazi, V., Flasseur, O., Barbieri, M., Benisty, M., Henning, Thomas, Ligi, R., Sissa, Elena, Zurlo, Alice, Boccaletti, Anthony, Cantalloube, F., Cheetham, Anthony, De Caprio, V., Feldt, Markus, Fusco, T., Gluck, L., Hagelberg, J., Lagrange, A. -M., Lazzoni, C., Madec, F., Maire, A. -L., Ménard, F., Meyer, M., Ramos, J., Rickman, E. L., Rouan, D., Schmidt, T., van der Plas, G., D’Orazi, V., De Caprio, V, Lagrange, A-M, Maire, A-L, Van der Plas, G, Janson, Markus, Asensio-Torres, Ruben, André, Damien, Bonnefoy, Mickaël, Delorme, Philippe, Reffert, Sabine, Desidera, Silvano, Langlois, M, Chauvin, G., Gratton, Raffaele, Bohn, Alexander J., Eriksson, Simon C., Marleau, Gabriel-Dominique, Mamajek, Eric E., Vigan, Arthur, Carson, Joseph C., Bohn, Alexander, Eriksson, Simon, Mamajek, Eric, Carson, Joseph, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Faculty of Aerospace Engineering [Delft], Delft University of Technology (TU Delft), Department of International Development, University of Oxford [Oxford], Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY PASADENA USA, Partenaires IRSTEA, Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), California Institute of Technology (CALTECH), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Space Sciences, Technologies and Astrophysics Research Institute (STAR), Université de Liège, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Konkoly Observatory, Research Centre for Astronomy and Earth Sciences [Budapest], Hungarian Academy of Sciences (MTA)-Hungarian Academy of Sciences (MTA), European Southern Observatory (ESO), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), INAF - Osservatorio Astrofisico di Arcetri (OAA), Istituto Nazionale di Astrofisica (INAF), INAF - Osservatorio Astronomico di Roma (OAR), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Department of Biochemistry and Molecular Biology, Mayo Clinic, INAF - Osservatorio Astronomico di Padova (OAPD), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), Collège de France (CdF (institution)), Département de Physique Nucléaire (ex SPhN) (DPHN), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Axe 4 : céramiques sous contraintes environnementales (SPCTS-AXE4), Science des Procédés Céramiques et de Traitements de Surface (SPCTS), Université de Limoges (UNILIM)-Ecole Nationale Supérieure de Céramique Industrielle (ENSCI)-Institut des Procédés Appliqués aux Matériaux (IPAM), Université de Limoges (UNILIM)-Université de Limoges (UNILIM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Limoges (UNILIM)-Ecole Nationale Supérieure de Céramique Industrielle (ENSCI)-Institut des Procédés Appliqués aux Matériaux (IPAM), Université de Limoges (UNILIM)-Université de Limoges (UNILIM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Grenoble (LAOG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Landessternwarte Königstuhl [ZAH] (LSW), Universität Heidelberg [Heidelberg], Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Stockholm University, Universität Heidelberg [Heidelberg] = Heidelberg University, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Departamento de Ingeniería Matemática [Santiago] (DIM), Universidad de Chile = University of Chile [Santiago] (UCHILE)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden, Institut für Astronomie und Astrophysik [Tübingen] (IAAT), Eberhard Karls Universität Tübingen = Eberhard Karls University of Tuebingen, Department of Physics and Astronomy [Rochester], University of Rochester [USA], College of Charleston, ANR-10-LABX-0056,OSUG@2020,Innovative strategies for observing and modelling natural systems(2010), and European Project: 678194,H2020,ERC-2015-STG,FALCONER(2016)

Subjects
planets and satellites: detection, Proper motion, 010504 meteorology & atmospheric sciences, Stellar mass, Brown dwarf, FOS: Physical sciences, Astrophysics, 01 natural sciences, Planet, 0103 physical sciences, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences, Physics, Earth and Planetary Astrophysics (astro-ph.EP), Astronomy and Astrophysics, Mass ratio, stars: early-type, Exoplanet, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Circumbinary planet, Astrophysics - Earth and Planetary Astrophysics, brown dwarfs
Abstract

Wide low-mass substellar companions are known to be very rare among low-mass stars, but appear to become increasingly common with increasing stellar mass. However, B-type stars, which are the most massive stars within ~150 pc of the Sun, have not yet been examined to the same extent as AFGKM-type stars in that regard. In order to address this issue, we launched the ongoing B-star Exoplanet Abundance Study (BEAST) to examine the frequency and properties of planets, brown dwarfs, and disks around B-type stars in the Scorpius-Centaurus (Sco-Cen) association; we also analyzed archival data of B-type stars in Sco-Cen. During this process, we identified a candidate substellar companion to the B9-type spectroscopic binary HIP 79098 AB, which we refer to as HIP 79098 (AB)b. The candidate had been previously reported in the literature, but was classified as a background contaminant on the basis of its peculiar colors. Here we demonstrate that the colors of HIP 79098 (AB)b are consistent with several recently discovered young and low-mass brown dwarfs, including other companions to stars in Sco-Cen. Furthermore, we show unambiguous common proper motion over a 15-year baseline, robustly identifying HIP 79098 (AB)b as a bona fide substellar circumbinary companion at a 345+/-6 AU projected separation to the B9-type stellar pair. With a model-dependent mass of 16-25 Mjup yielding a mass ratio of, 9 pages, 6 figures, accepted for publication in A&A

Published
2019
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5. First resolved observations of a highly asymmetric debris disc around HD 160305 with VLT/SPHERE

Author

Perrot, Clément, primary, Thebault, Philippe, additional, Lagrange, Anne-Marie, additional, Boccaletti, Anthony, additional, Vigan, Arthur, additional, Desidera, Silvano, additional, Augereau, Jean-Charles, additional, Bonnefoy, Mickael, additional, Choquet, Élodie, additional, Kral, Quentin, additional, Loh, Alan, additional, Maire, Anne-Lise, additional, Ménard, François, additional, Messina, Sergio, additional, Olofsson, Johan, additional, Gratton, Raffaele, additional, Biller, Beth, additional, Brandner, Wolfgang, additional, Buenzli, Esther, additional, Chauvin, Gaël, additional, Cheetham, Anthony, additional, Daemgen, Sebastien, additional, Delorme, Philippe, additional, Feldt, Markus, additional, Lagadec, Eric, additional, Langlois, Maud, additional, Lannier, Justine, additional, Mesa, Dino, additional, Mouillet, David, additional, Peretti, Sébastien, additional, Janin-Potiron, Pierre, additional, Salter, Graeme, additional, Sissa, Elena, additional, Roux, Alain, additional, Llored, Marc, additional, Buey, Jean-Tristan, additional, Pavlov, Alexei, additional, Weber, Luc, additional, and Petit, Cyril, additional

Published
2019
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6. Observation of extrasolar planets at various ages

Author

Sissa, Elena

Subjects
stars: individual: T Cha, stars: individual: HIP65426, FIS/05 Astronomia e astrofisica, protoplanetary disks, protoplanetary disks, planetary systems, methods: data analysis, stars: individual: T Cha, stars: individual: HD100546, stars: individual: Lk Ca 15, stars: individual: GQ Lup,stars: individual: HIP80591, stars: individual: HIP65426, techniques: high angular resolution, techniques: image processing, techniques: spectroscopic, binaries: visual, stars: activity, techniques: radial velocities, stars: individual: GQ Lup, techniques: high angular resolution, techniques: image processing, methods: data analysis, binaries: visual, Settore FIS/05 - Astronomia e Astrofisica, stars: activity, techniques: radial velocities, Astrophysics::Solar and Stellar Astrophysics, stars: individual: HD100546, Astrophysics::Earth and Planetary Astrophysics, planetary systems, Astrophysics::Galaxy Astrophysics, techniques: spectroscopic, stars: individual: Lk Ca 15, stars: individual: HIP80591
Abstract

The search and characterization of extrasolar planets is one of the main topics of current astronomy, with the ultimate goals of understanding the formation and evolution of planetary systems, the general conditions for the formation of life-friendly environments, and possibly detecting signature of extra-solar life. In the last decades the research of extrasolar planets underwent a steep increase of interest and different methods of detection were developed. Each of them has its own merit and lack in studying the extrasolar system architecture and the characteristics of extrasolar planets. Stars and their planetary entourage form and grow together, at least in most cases, tied by the circumstellar disk. A unique theory that can describe all the processes that happen between the protostellar cloud collapse and the final system stabilization is not available at the moment. Indirect methods are very useful to study more evolved systems, where the protoplanetary disk contribution is negligible, in their innermost regions. On the other hand, direct imaging with high-contrast instruments offers the possibility to study the early phases of the planet formation, that are not accessible to other indirect methods of planets detection, and plays a key role in current planet formation theories. This thesis focuses on the capabilities of direct imaging with SPHERE, the new high-contrast imager of VLT, in detecting planets at different stages of their evolution, coupled with radial velocities observations of old systems obtained from SARG, the old TNG echelle spectrograph. Chapter 1 briefly introduces the planet formation and evolution theories with the most important exoplanets research methods. Chapter 2 describes the SPHERE instrument used for the majority of the results presented in this thesis. In Chapter 3 I present the case of four young objects. I exploit the SPHERE visible channel to study Z CMa jets, and the near-IR channel for HD 100546 and T Cha, looking for the presence of planets. At the same time, I was able to study in detail the circumplanetary disk of HD 100546 in a quite wide spectral range: in the dedicated Section I show that the system brightest structures suggest the presence of at least three gaps in the inner regions of the disk, coupled with other structures, such as spiral arms. I detected a diffuse source at the location of the claimed planet HD 100546 b, but the nature of this emission is, however, still unknown. Lastly, LkCa15 was studied both in the visible and in the near-IR of SPHERE. In Chapter 4 I present the study of the accretion signature in a few objects. GQ Lup b accretion was observed both in H_alpha and in Paschen beta, exploiting all three SPHERE subsystems. Two systems that have already cleaned out their surroundings from gas and dust are presented in Chapter 5: HIP 80591 and HD 65426. In the latter, I first found out that one companion candidate had high probability to be bound to the star due to its position and it spectral features. These findings were later confirmed by a deeper analysis and follow up observations that demonstrate HD 65426 b, the companion I studied, is a warm Jupiter-like planet with mass between 6 and 12 M_J. In Chapter 6, I study the chromospheric activity in older binary stars in order to detect a radial velocity signal hidden by the Doppler shift induced by the activity. I found out that Ha-excess, an index based on the Halpha line, is a good indicator of the star activity when the log_RHK' index is not available and can be used also to infer stellar ages in case of stars younger then 1.5 Gyr. Moreover, HD 76073 B shows a high radial velocities scatter that can be explained by the presence of a low-mass companion (Sissa et al. 2016). Finally, in Chapter 7 I give the conclusions and explain future prospects. Appendixes are dedicated to the more technical aspects of my work, that were needed to improve instrument capabilities and data reduction, and to better defining the instrument set-ups needed to achieve different scientific aims.

Published
2017

8. First resolved observations of a highly asymmetric debris disc around HD 160305 with VLT/SPHERE

Author

Perrot, Clément, Thébault, Philippe, Lagrange, Anne-Marie, Boccaletti, Anthony, Vigan, Arthur, Desidera, Silvano, Ausgereau, Jean-Charles, Bonnefoy, Mickaël, Choquet, Élodie, Kral, Quentin, Loh, Alan, Maire, Anne-Lise, Ménard, François, Messina, Sergio, Olofsson, Johan, Gratton, Raffaele, Biller, Beth A., Brandner, Wolfgang, Buenzli, Esther, Chauvin, Gaël, Cheetham, Anthony, Daemgen, Sebastien, Delorme, Philippe, Feldt, Markus, Langlois, Maud, Lannier, Justine, Mesa, Dino, Mouillet, David, Peretti, Sébastien, Janin-Potiron, Pierre, Salter, Graeme, Sissa, Elena, Roux, Alain, Llored, Marc, Buey, Jean-Tristan, Pavlov, Alexei, Weber, Luc, and Petit, Cyril

Subjects
planet-disk interactions, 13. Climate action, scattering, techniques: high angular resolution, techniques: image processing, Astrophysics::Earth and Planetary Astrophysics, methods: observational, stars: individual: HD160305, Astrophysics::Galaxy Astrophysics
Abstract

Context. Direct imaging of debris discs gives important information about their nature, their global morphology, and allows us to identify specific structures possibly in connection with the presence of gravitational perturbers. It is the most straightforward technique to observe planetary systems as a whole. Aims. We present the first resolved images of the debris disc around the young F-type star HD 160305, detected in scattered light using the VLT/SPHERE instrument in the near infrared. Methods. We used a post-processing method based on angular differential imaging and synthetic images of debris discs produced with a disc modelling code (GRaTer) to constrain the main characteristics of the disc around HD 160305. All of the point sources in the field of the IRDIS camera were analysed with an astrometric tool to determine whether they are bound objects or background stars. Results. We detect a very inclined (~82°) ring-like debris disc located at a stellocentric distance of about 86 au (deprojected width ~27 au). The disc displays a brightness asymmetry between the two sides of the major axis, as can be expected from scattering properties of dust grains. We derive an anisotropic scattering factor g > 0.5. A second right-left asymmetry is also observed with respect to the minor axis. We measure a surface brightness ratio of 0.73 ± 0.18 between the bright and the faint sides. Because of the low signal-to-noise ratio (S/N) of the images we cannot easily discriminate between several possible explanations for this left-right asymmetry, such as perturbations by an unseen planet, the aftermath of the breakup of a massive planetesimal, or the pericenter glow effect due to an eccentric ring. Two epochs of observations allow us to reject the companionship hypothesis for the 15 point sources present in the field., Astronomy & Astrophysics, 626, ISSN:0004-6361, ISSN:1432-0746

9. Three Years of SPHERE: The Latest View of the Morphology and Evolution of Protoplanetary Discs

Author

Garufi, Antonio, Benisty, Myriam, Stolker, Tomas, Avenhaus, Henning, De Boer, Jos, Pohl, Adriana, Quanz, Sascha P., Dominik, Carsten, Ginski, Christian, Thalmann, Christian, Van Boekel, Roy, Boccaletti, Anthony, Henning, Thomas, Janson, Markus, Salter, Graeme, Schmid, Hans Martin, Sissa, Elena, Langlois, Maud, Beuzit, Jean-Luc, Chauvin, Gaël, Mouillet, David, Augereau, Jean-Charles, Bazzon, Andreas, Biller, Beth, Bonnefoy, Mickael, Buenzli, Esther, Cheetham, Anthony, Daemgen, Sebastian, Desidera, Silvano, Engler, Natalia, Feldt, Markus, Girard, Julien, Gratton, Raffaele, Hagelberg, Janis, Keller, Christoph, Keppler, Miriam, Kenworthy, Matthew, Kral, Quentin, Lopez, Bruno, Maire, Anne-Lise, Menard, François, Mesa, Dino, Messina, Sergio, Meyer, Michael R., Milli, Julien, Min, Michiel, Muller, André, Olofsson, Johan, Pawellek, Nicole, Pinte, Christophe, Szulagyi, Judit, Vigan, Arthur, Wahhaj, Zahed, Waters, Rens, and Zurlo, Alice

Subjects
010308 nuclear & particles physics, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, 01 natural sciences, Astrophysics::Galaxy Astrophysics
Abstract

Spatially resolving the immediate surroundings of young stars is a key challenge for the planet formation community. SPHERE on the VLT represents an important step forward by increasing the opportunities offered by optical or near-infrared imaging instruments to image protoplanetary discs. The Guaranteed Time Observation Disc team has concentrated much of its efforts on polarimetric differential imaging, a technique that enables the efficient removal of stellar light and thus facilitates the detection of light scattered by the disc within a few au from the central star. These images reveal intriguing complex disc structures and diverse morphological features that are possibly caused by ongoing planet formation in the disc. An overview of the recent advances enabled by SPHERE is presented., Published in The Messenger vol. 169, pp. 32-37, September 2017.

10. First scattered light detection of a nearly edge-on transition disk around the T Tauri star RY Lupi

Author

Langlois, Maud, Pohl, Adriana, Lagrange, Anne-Marie, Maire, Anne-Lise, Mesa, Dino, Boccaletti, Anthony, Gratton, Raffaele G., Denneulin, Laurence, Klahr, Hubert, Vigan, Arthur, Benisty, Myriam, Dominik, Carsten, Bonnefoy, Mickaël, Ménard, François, Avenhaus, Henning, Cheetham, Anthony, Van Boekel, Roy, De Boer, Jos, Chauvin, Gaël, Desidera, Silvano, Feldt, Markus, Galicher, Raphaël, Ginski, Christian, Girard, Julien H., Henning, Thomas, Janson, Markus, Kopytova, Taisiya G., Kral, Quentin, Ligi, Roxanne, Messina, Sergio, Peretti, Sébastien, Pinte, Christophe, Sissa, Elena, Stolker, Tomas, Zurlo, Alice, Magnard, Yves, Blanchard, Philippe, Buey, Tristan, Suárez Valles, Marcos, Cascone, Enrico, Möller-Nilsson, Ole, Weber, Luc, Petit, Cyril, and Pragt, Johan H.

Subjects
planet-disk interactions, techniques: polarimetric, 13. Climate action, protoplanetary disks, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, methods: observational, Astrophysics::Galaxy Astrophysics, methods: numerical
Abstract

Context. Transition disks are considered sites of ongoing planet formation, and their dust and gas distributions could be signposts of embedded planets. The transition disk around the T Tauri star RY Lup has an inner dust cavity and displays a strong silicate emission feature. Aims. Using high-resolution imaging we study the disk geometry, including non-axisymmetric features, and its surface dust grain, to gain a better understanding of the disk evolutionary process. Moreover, we search for companion candidates, possibly connected to the disk. Methods. We obtained high-contrast and high angular resolution data in the near-infrared with the VLT/SPHERE extreme adaptive optics instrument whose goal is to study the planet formation by detecting and characterizing these planets and their formation environments through direct imaging. We performed polarimetric imaging of the RY Lup disk with IRDIS (at 1.6 μm), and obtained intensity images with the IRDIS dual-band imaging camera simultaneously with the IFS spectro-imager (0.9–1.3 μm). Results. We resolved for the first time the scattered light from the nearly edge-on circumstellar disk around RY Lup, at projected separations in the 100 au range. The shape of the disk and its sharp features are clearly detectable at wavelengths ranging from 0.9 to 1.6 μm. We show that the observed morphology can be interpreted as spiral arms in the disk. This interpretation is supported by in-depth numerical simulations. We also demonstrate that these features can be produced by one planet interacting with the disk. We also detect several point sources which are classified as probable background objects., Astronomy & Astrophysics, 614, ISSN:0004-6361, ISSN:1432-0746

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