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1. Orbital and dynamical analysis of the system around HR 8799 New astrometric epochs from VLT/SPHERE and LBT/LUCI

Author

A. Zurlo, K. Goździewski, C. Lazzoni, D. Mesa, P. Nogueira, S. Desidera, R. Gratton, F. Marzari, M. Langlois, E. Pinna, G. Chauvin, P. Delorme, J. H. Girard, J. Hagelberg, Th. Henning, M. Janson, E. Rickman, P. Kervella, H. Avenhaus, T. Bhowmik, B. Biller, A. Boccaletti, M. Bonaglia, M. Bonavita, M. Bonnefoy, F. Cantalloube, A. Cheetham, R. Claudi, V. D’Orazi, M. Feldt, R. Galicher, E. Ghose, A.-M. Lagrange, H. le Coroller, R. Ligi, M. Kasper, A.-L. Maire, F. Medard, M. Meyer, S. Peretti, C. Perrot, A. T. Puglisi, F. Rossi, B. Rothberg, T. Schmidt, E. Sissa, A. Vigan, Z. Wahhaj, 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), Centre de Recherche Astrophysique de Lyon (CRAL), 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), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), 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)-Météo-France -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)-Météo-France, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Observatoire de la Côte d'Azur (OCA), and Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), planet-disk interactions, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], planets and satellites: dynamical evolution and stability, FOS: Physical sciences, techniques: image processing, Astronomy and Astrophysics, instrumentation: adaptive optics, dynamical evolution and stability, stars: individual: HR8799, astrometry, techniques: image processing [planets and satellites], Astrophysics - Solar and Stellar Astrophysics, [SDU]Sciences of the Universe [physics], Space and Planetary Science, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics - Earth and Planetary Astrophysics
Abstract

Context. HR 8799 is a young planetary system composed of four planets and a double debris belt. Being the first multi-planetary system discovered with the direct imaging technique, it has been observed extensively since 1998. This wide baseline of astrometric measurements, counting over 50 observations in 20 years, permits a detailed orbital and dynamical analysis of the system. Aims. To explore the orbital parameters of the planets, their dynamical history, and the planet-to-disk interaction, we made follow-up observations of the system during the VLT/SPHERE guaranteed time observation program. We obtained 21 observations, most of them in favorable conditions. In addition, we observed HR 8799 with the instrument LUCI at the Large Binocular Telescope (LBT). Methods. All the observations were reduced with state-of-the-art algorithms implemented to apply the spectral and angular differential imaging method. We re-reduced the SPHERE data obtained during the commissioning of the instrument and in three open-time programs to have homogeneous astrometry. The precise position of the four planets with respect to the host star was calculated by exploiting the fake negative companions method. We obtained an astrometric precision of the order of 6 mas in the worst case and 1 mas in the best case. To improve the orbital fitting, we also took into account all of the astrometric data available in the literature. From the photometric measurements obtained in different wavelengths, we estimated the masses of the planets following the evolutionary models. Results. We obtained updated parameters for the orbits with the assumption of coplanarity, relatively small eccentricities, and periods very close to the 2:1 resonance. We also refined the dynamical mass of each planet and the parallax of the system (24.49 +/- 0.07 mas), which overlap with the recent Gaia eDR3/DR3 estimate. Hydrodynamical simulations suggest that inward migration of the planets caused by the interaction with the disk might be responsible for the planets being locked in resonance. We also conducted detailed N-body simulations indicating possible positions of a putative fifth planet with a mass below the present detection limits of similar or equal to 3 M-Jup., Astronomy & Astrophysics, 666, ISSN:0004-6361, ISSN:1432-0746

Published
2022
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2. SPHERE adaptive optics performance for faint targets

Author

M. I. Jones, J. Milli, I. Blanchard, Z. Wahhaj, R. J. De Rosa, C. Romero, and N. Ihanec

Subjects
Space and Planetary Science, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract

Context: High contrast imaging is a powerful technique to detect and characterize planetary companions at large orbital separations from their parent stars. Aims: We aim at studying the limiting magnitude of the VLT/SPHERE Adaptive Optics system and the corresponding instrument performance for faint targets (G $\ge$ 11.0 mag). Methods: We computed coronagraphic H-band raw contrast at 300 [mas] and FWHM of the non-coronagraphic PSF, for a total of 111 different stars observed between 2016 and 2022 with IRDIS. For this, we processed a large number of individual frames that were obtained under different atmospheric conditions. We then compared the resulting raw contrast and the PSF shape as a function of the visible wave front sensor instant flux which scales with the G-band stellar magnitude. We repeated this analysis for the top 10\% and 30\% best turbulence conditions in Cerro Paranal. Results: We found a strong decrease in the coronagraphic achievable contrast for star fainter than G $\sim$ 12.5 mag, even under the best atmospheric conditions. In this regime, the AO correction is dominated by the read-out noise of the WFS detector. In particular we found roughly a factor ten decrease in the raw contrast ratio between stars with G $\sim$ 12.5 and G $\sim$ 14.0 mag. Similarly, we observe a sharp increase in the FWHM of the non-coronagraphic PSF beyond G $\sim$ 12.5 mag, and a corresponding decrease in the strehl ratio from $\sim$ 50\% to $\sim$ 20\% for the faintest stars. Although these trend are observed for the two turbulence categories, the decrease in the contrast ratio and PSF sharpness is more pronounced for poorer conditions., Comment: Submitted to A&A

Published
2022
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3. Increasing the raw contrast of VLT/SPHERE with the dark hole technique

Author

A. Potier, J. Mazoyer, Z. Wahhaj, P. Baudoz, G. Chauvin, R. Galicher, and G. Ruane

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Space and Planetary Science, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics - Earth and Planetary Astrophysics
Abstract

Context. Direct imaging of exoplanets takes advantage of state-of-the-art adaptive optics (AO) systems, coronagraphy, and post-processing techniques. Coronagraphs attenuate starlight to mitigate the unfavorable flux ratio between an exoplanet and its host star. AO systems provide diffraction-limited images of point sources and minimize optical aberrations that would cause starlight to leak through coronagraphs. Post-processing techniques then estimate and remove residual stellar speckles such as noncommon path aberrations (NCPAs) and diffraction from telescope obscurations. Aims. We aim to demonstrate an efficient method to minimize the speckle intensity due to NCPAs during an observing night on VLT/SPHERE. Methods. We implement an iterative dark-hole (DH) algorithm to remove stellar speckles on-sky before a science observation. It uses a pair-wise probing estimator and a controller based on electric field conjugation. This work presents the first such on-sky minimization of speckles with a DH technique on SPHERE. Results. We show the standard deviation of the normalized intensity in the raw images is reduced by a factor of up to 5 in the corrected region with respect to the current calibration strategy under median conditions for VLT. This level of contrast performance obtained with only 1 min of exposure time reaches median performances on SPHERE that use post-processing methods requiring 1h-long sequences of observations. We also present an alternative calibration method that takes advantage of the starlight coherence and improves the post-processed contrast levels rms by a factor of about 3. Conclusions. This on-sky demonstration represents a decisive milestone for the future design, development, and observing strategy of the next generation of ground-based exoplanet imagers for 10m to 40m telescope., Accepted in Astronomy & Astrophysics

Published
2022
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5. A triple star in disarray: Multi-epoch observations of T Tauri with VLT-SPHERE and LBT-LUCI

Author

M. Kasper, K. K. R. Santhakumari, T. M. Herbst, R. van Boekel, F. Menard, R. Gratton, R. G. van Holstein, M. Langlois, C. Ginski, A. Boccaletti, M. Benisty, J. de Boer, P. Delorme, S. Desidera, C. Dominik, J. Hagelberg, T. Henning, J. Heidt, R. Köhler, D. Mesa, S. Messina, A. Pavlov, C. Petit, E. Rickman, A. Roux, F. Rigal, A. Vigan, Z. Wahhaj, A. Zurlo, Low Energy Astrophysics (API, FNWI), European Southern Observatory (ESO), INAF - Osservatorio Astronomico di Padova (OAPD), Istituto Nazionale di Astrofisica (INAF), Max Planck Institute for Medical Research [Heidelberg], Max-Planck-Gesellschaft, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), 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), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], 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), 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)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Université de Genève (UNIGE), Max-Planck-Institut für Astronomie (MPIA), Universität Wien, INAF - Osservatorio Astrofisico di Catania (OACT), DOTA, ONERA, Université Paris Saclay [Palaiseau], ONERA-Université Paris-Saclay, 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), European Southern Observatory [Santiago] (ESO), and Universidad Diego Portales [Santiago] (UDP)

Subjects
Physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], 010308 nuclear & particles physics, Star formation, Star wind, Extinction (astronomy), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, High angular resolution astronomy, Stars, Photometry (astronomy), T Tauri star, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, 0103 physical sciences, Outflow, Multiple star, Circumbinary planet, Adaptive optics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Line (formation)
Abstract

T Tauri remains an enigmatic triple star for which neither the evolutionary state of the stars themselves, nor the geometry of the complex outflow system is completely understood. Eight-meter class telescopes equipped with state-of-the-art adaptive optics provide the spatial resolution necessary to trace tangential motion of features over a timescale of a few years, and they help to associate them with the different outflows. We used J-, H-, and K-band high-contrast coronagraphic imaging with VLT-SPHERE recorded between 2016 and 2018 to map reflection nebulosities and obtain high precision near-infrared (NIR) photometry of the triple star. We also present molecular hydrogen emission maps of the 1-0 S(1) line at 2.122 micron obtained with LBT-LUCI during its commissioning period at the end of 2016. The data reveal a number of new features in the system, some of which are seen in reflected light and some are seen in H2 emission; furthermore, they can all be associated with the main outflows. The tangential motion of the features provides compelling evidence that T Tauri Sb drives the southeast-northwest outflow. T Tauri Sb has recently faded probably because of increased extinction as it passes through the southern circumbinary disk. While T Tauri Sb is approaching periastron, T Tauri Sa instead has brightened and is detected in all our J-band imagery for the first time., Comment: 10 pages, 9 figures, accepted for publication in A&A

Published
2020
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6. Unveiling the β Pictoris system, coupling high contrast imaging, interferometric, and radial velocity data

Author

Christian Straubmeier, J. Hagelberg, Anne-Marie Lagrange, A. Grandjean, Frank Eisenhauer, Myriam Benisty, Silvano Desidera, R. Asensio-Torres, Anne-Lise Maire, M. Nowak, Thibaut Paumard, F. Cantalloube, Jens Kammerer, Yann Clénet, P. T. de Zeeuw, Matthew Horrobin, Karine Perraut, Eric Gendron, O. Pfuhl, L. Pueyo, Stefan Gillessen, Stefan Hippler, John Monnier, Raphael Galicher, P. Thebault, Gael Chauvin, C. Babusiaux, J. Wang, Wolfgang Brandner, L. Kreidberg, P. Léna, V. Lapeyrère, J. M. Girard, Sylvestre Lacour, G. Rodríguez-Coira, Guy Perrin, Matthew A. Kenworthy, H. Le Coroller, G. Heissel, F. Galland, V. Christiaens, P. Delorme, V. Coudé du Foresto, E. Choquet, Matthias Samland, Hervé Beust, Miriam Keppler, Odele Straub, Mickael Bonnefoy, Gilles Duvert, Andreas Eckart, Z. Wahhaj, T. Stolker, A. Zurlo, C. Paladini, F. Vincent, G. Otten, M. Janson, O. Flasseur, J.-B. Le Bouquin, A. Mérand, Felix Widmann, G. Rousset, Jinyi Shangguan, N. Meunier, Feng Gao, R. Gratton, A. Vigan, Paul Mollière, Jean-Phillipe Berger, P. Rubini, P. Kervella, T. Henning, António Amorim, T. Schmidt, Julien Woillez, Xavier Haubois, Anthony Boccaletti, Maud Langlois, Q. Kral, P. Garcia, Thomas Ott, L. Rodet, B. Charnay, R. Garcia Lopez, Reinhard Genzel, Sergio Messina, 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), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), 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)-Météo-France -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)-Météo-France, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), 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), Centre de Recherche Astrophysique de Lyon (CRAL), 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), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), European Southern Observatory [Santiago] (ESO), European Southern Observatory (ESO), CENTRA-SIM, IDL-Faculdade de Ciencias da Universidade de Lisboa, Departamento de Astronomía, Universidad de Chile = University of Chile [Santiago] (UCHILE), Max-Planck-Institut für Radioastronomie (MPIFR), Max Planck Institute for Extraterrestrial Physics (MPE), Max-Planck-Gesellschaft, CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire des Combustibles Uranium (LCU), Service d'Analyses, d'Elaboration, d'Expérientations et d'Examens des combustibles (SA3E), Département d'Etudes des Combustibles (DEC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Département d'Etudes des Combustibles (DEC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Physikalisches Institut [Köln], Universität zu Köln = University of Cologne, Max-Planck-Institut für Astronomie (MPIA), University of Freiburg [Freiburg], Space Telescope Science Institute (STSci), German Research Centre for Geosciences - Helmholtz-Centre Potsdam (GFZ), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), the GRAVITY Collaboration, 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), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Centre d'Immunologie de Marseille - Luminy (CIML), Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Observatoire de Paris - Site de Paris (OP), Universität zu Köln, 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), Institut de Recherche pour le Développement (IRD), and Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)

Subjects
planets and satellites: detection, media_common.quotation_subject, Context (language use), Astrophysics, 01 natural sciences, Planet, radial velocities -planets and satellites, 0103 physical sciences, techniques: radial velocities, Astrophysics::Solar and Stellar Astrophysics, Eccentricity (behavior), 10. No inequality, planets and satellites: fundamental parameters, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, media_common, Orbital elements, Physics, [PHYS]Physics [physics], detectionplanets and satellites, 010308 nuclear & particles physics, high angular resolution -techniques, Giant planet, techniques: high angular resolution, Astronomy and Astrophysics, Astrometry, Planetary system, Radial velocity, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], techniques, fundamental parameters
Abstract

Context. The nearby and young β Pictoris system hosts a well resolved disk, a directly imaged massive giant planet orbiting at ≃9 au, as well as an inner planet orbiting at ≃2.7 au, which was recently detected through radial velocity (RV). As such, it offers several unique opportunities for detailed studies of planetary system formation and early evolution. Aims. We aim to further constrain the orbital and physical properties of β Pictoris b and c using a combination of high contrast imaging, long base-line interferometry, and RV data. We also predict the closest approaches or the transit times of both planets, and we constrain the presence of additional planets in the system. Methods. We obtained six additional epochs of SPHERE data, six additional epochs of GRAVITY data, and five additional epochs of RV data. We combined these various types of data in a single Markov-chain Monte Carlo analysis to constrain the orbital parameters and masses of the two planets simultaneously. The analysis takes into account the gravitational influence of both planets on the star and hence their relative astrometry. Secondly, we used the RV and high contrast imaging data to derive the probabilities of presence of additional planets throughout the disk, and we tested the impact of absolute astrometry. Results. The orbital properties of both planets are constrained with a semi-major axis of 9.8 ± 0.4 au and 2.7 ± 0.02 au for b and c, respectively, and eccentricities of 0.09 ± 0.1 and 0.27 ± 0.07, assuming the HIPPARCOS distance. We note that despite these low fitting error bars, the eccentricity of β Pictoris c might still be over-estimated. If no prior is provided on the mass of β Pictoris b, we obtain a very low value that is inconsistent with what is derived from brightness-mass models. When we set an evolutionary model motivated prior to the mass of β Pictoris b, we find a solution in the 10–11 MJup range. Conversely, β Pictoris c’s mass is well constrained, at 7.8 ± 0.4 MJup, assuming both planets are on coplanar orbits. These values depend on the assumptions on the distance of the β Pictoris system. The absolute astrometry HIPPARCOS-Gaia data are consistent with the solutions presented here at the 2σ level, but these solutions are fully driven by the relative astrometry plus RV data. Finally, we derive unprecedented limits on the presence of additional planets in the disk. We can now exclude the presence of planets that are more massive than about 2.5 MJup closer than 3 au, and more massive than 3.5 MJup between 3 and 7.5 au. Beyond 7.5 au, we exclude the presence of planets that are more massive than 1–2 MJup. Conclusions. Combining relative astrometry and RVs allows one to precisely constrain the orbital parameters of both planets and to give lower limits to potential additional planets throughout the disk. The mass of β Pictoris c is also well constrained, while additional RV data with appropriate observing strategies are required to properly constrain the mass of β Pictoris b.

Published
2020
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7. Calibration of quasi-static aberrations in exoplanet direct-imaging instruments with a Zernike phase-mask sensor

Author

A. Vigan, K. Dohlen, M. N’Diaye, F. Cantalloube, J. H. Girard, J. Milli, J.-F. Sauvage, Z. Wahhaj, G. Zins, J.-L. Beuzit, A. Caillat, A. Costille, J. Le Merrer, D. Mouillet, and S. Tourenq

Subjects
Space and Planetary Science, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract

Coronagraphic imaging of exoplanets using ground-based instruments on large telescopes is intrinsically limited by speckles induced by uncorrected aberrations. These aberrations originate from the imperfect correction of the atmosphere by an extreme adaptive optics system; from static optical defects; or from small opto-mechanical variations due to changes in temperature, pressure, or gravity vector. More than the speckles themselves, the performance of high-contrast imagers is ultimately limited by their temporal stability, since most post-processing techniques rely on difference of images acquired at different points in time. Identifying the origin of the aberrations and the timescales involved is therefore crucial to understanding the fundamental limits of dedicated high-contrast instruments. We previously demonstrated the use of a Zernike wavefront sensor called ZELDA for sensing non-common path aberrations (NCPA) in VLT/SPHERE. We now use ZELDA to investigate the stability of the instrumental aberrations using 5 long sequences of measurements obtained at high cadence on the internal source. Our study reveals two regimes of decorrelation of the NCPA. The first, with a characteristic timescale of a few seconds and an amplitude of a few nanometers, is induced by a fast internal turbulence within the enclosure. The second is a slow quasi-linear decorrelation on the order of a few $10^{-3}$ nm rms/s that acts on timescales from minutes to hours. We use coronagraphic image reconstruction to demonstrate that these two NCPA contributions have a measurable impact on differences of images, and that the fast internal turbulence is a dominating term over to the slow linear decorrelation. We also use dedicated sequences where the derotator and atmospheric dispersion compensators emulate a real observation to demonstrate the importance of performing observations symmetric around the meridian., 14 pages, 15 figures. Accepted for publication in A&A

Published
2022
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9. A search for accreting young companions embedded in circumstellar disks: High-contrast Hα imaging with VLT/SPHERE

Author

Janis Hagelberg, Christophe Pinte, G. van der Plas, Emmanuel Hugot, Markus Janson, Anne-Marie Lagrange, G. Cugno, Alexander J. Bohn, F. Rigal, J. Pragt, Henning Avenhaus, Tomas Stolker, Philippe Feautrier, Pierre Baudoz, C. Mordasini, Yves Magnard, Arthur Vigan, Anne-Lise Maire, G. Chauvin, Anthony Cheetham, Carsten Dominik, A. Zurlo, H. M. Schmid, Michael Meyer, Julien Milli, M. Feldt, Julien Girard, M. Bonnefoy, R. G. Gratton, Silvano Desidera, Esther Buenzli, Ch. Ginski, R. Roelfsema, Francois Menard, Z. Wahhaj, S. Hunziker, Judit Szulágyi, Sascha P. Quanz, R. van Boekel, Maud Langlois, and Low Energy Astrophysics (API, FNWI)

Subjects
Physics, 010308 nuclear & particles physics, Astronomy and Astrophysics, Astrophysics, high angular resolution, Planets and satellites: detection, formation, Planet-disk interactions, Planetary systems [Techniques], 01 natural sciences, Circumstellar disk, Accretion (astrophysics), Photometry (optics), Stars, Space and Planetary Science, Planet, 0103 physical sciences, H-alpha, Continuum (set theory), Protoplanet, 010303 astronomy & astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

Aims: We want to detect and quantify observables related to accretion processes occurring locally in circumstellar disks, which could be attributed to young forming planets. We focus on objects known to host protoplanet candidates and/or disk structures thought to be the result of interactions with planets. Methods: We analyzed observations of 6 young stars (age $3.5-10$ Myr) and their surrounding environments with the SPHERE/ZIMPOL instrument on the VLT in the H$\alpha$ filter (656 nm) and a nearby continuum filter (644.9 nm). Results: We re-detect the known accreting M-star companion HD142527 B with the highest published signal to noise to date in both H$\alpha$ and the continuum. We derive new astrometry ($r = 62.8^{+2.1}_{-2.7}$ mas and $\text{PA} = (98.7\,\pm1.8)^\circ$) and photometry ($\Delta$N_Ha=$6.3^{+0.2}_{-0.3}$ mag, $\Delta$B_Ha=$6.7\pm0.2$ mag and $\Delta$Cnt_Ha=$7.3^{+0.3}_{-0.2}$ mag) for the companion in agreement with previous studies, and estimate its mass accretion rate ($\dot{M}\approx1-2\,\times10^{-10}\,M_\odot\text{ yr}^{-1}$). A faint point-like source around HD135344 B (SAO206462) is also investigated, but a second deeper observation is required to reveal its nature. No other companions are detected. In the framework of our assumptions we estimate detection limits at the locations of companion candidates around HD100546, HD169142 and MWC758 and calculate that processes involving H$\alpha$ fluxes larger than $\sim8\times10^{-14}-10^{-15}\,\text{erg/s/cm}^2$ ($\dot{M}>10^{-10}-10^{-12}\,M_\odot\text{ yr}^{-1}$) can be excluded. Furthermore, flux upper limits of $\sim10^{-14}-10^{-15}\,\text{erg/s/cm}^2$ ($\dot{M}, Comment: Accepted for publication in A&A (20 pages, 18 figures)

Published
2019

11. Spectral and atmospheric characterization of 51 Eridani b using VLT/SPHERE

Author

M. Samland, P. Mollière, M. Bonnefoy, A.-L. Maire, F. Cantalloube, A. C. Cheetham, D. Mesa, R. Gratton, B. A. Biller, Z. Wahhaj, J. Bouwman, W. Brandner, D. Melnick, J. Carson, M. Janson, T. Henning, D. Homeier, C. Mordasini, M. Langlois, S. P. Quanz, R. van Boekel, A. Zurlo, J. E. Schlieder, H. Avenhaus, J.-L. Beuzit, A. Boccaletti, M. Bonavita, G. Chauvin, R. Claudi, M. Cudel, S. Desidera, M. Feldt, T. Fusco, R. Galicher, T. G. Kopytova, A.-M. Lagrange, H. Le Coroller, P. Martinez, O. Moeller-Nilsson, D. Mouillet, L. M. Mugnier, C. Perrot, A. Sevin, E. Sissa, A. Vigan, L. Weber, Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, International Max Planck Research School for Astronomy and Cosmic Physics (University of Heidelberg), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-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 Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-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 Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), DOTA, ONERA, Université Paris Saclay [Châtillon], ONERA-Université Paris-Saclay, Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), INAF - Osservatorio Astronomico di Padova (OAPD), Istituto Nazionale di Astrofisica (INAF), Institute for Astronomy [Edinburgh] (IfA), University of Edinburgh, European Southern Observatory [Santiago] (ESO), European Southern Observatory (ESO), College of Charleston, Stockholm University, Universität Heidelberg [Heidelberg], University of Bern, 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-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), 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), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology in Zürich [Zürich] (ETH Zürich), Universidad de Santiago de Chile [Santiago] (USACH), Universidad Diego Portales [Santiago] (UDP), NASA Ames Research Center (ARC), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Arizona State University [Tempe] (ASU), Ural Federal University [Ekaterinburg] (UrFU), Observatoire de la Côte d'Azur (OCA), Centre National de la Recherche Scientifique (CNRS), 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]), DOTA, ONERA, Université Paris Saclay (COmUE) [Châtillon], ONERA-Université Paris Saclay (COmUE), Université de Genève = University of Geneva (UNIGE), Universität Heidelberg [Heidelberg] = Heidelberg University, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), 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), Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), 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)-Météo-France -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)-Météo-France, ONERA, ISDC, Geneva Observatory, University of Geneva, INAF-Osservatorio Astronomico di Padova, Institute for Astronomy, Blackford Hill, European Southern Observatory, Department of Physics and Astronomy, College of Charleston, Department of Astronomy, Stockholm University, AlbaNova University Center, 106 91, Stockholm, Sweden, Zentrum für Astronomie der Universität Heidelberg (ZAH), University of Bern (UBERN), Institute for Astronomy, Department of Physics, ETH Zürich, Departamento de Astronomía, Universidad de Chile, and NASA Ames Research Center (NASA Ames)

Subjects
Solar System, IMAGE PROCESSING, 010504 meteorology & atmospheric sciences, HIGH ANGULAR RESOLUTIONS [TECHNIQUES], Metallicity, Brown dwarf, ATMOSPHERES [PLANETS AND SATELLITES], FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, IMAGE PROCESSING [TECHNIQUES], 01 natural sciences, Photometry (optics), SPECTROSCOPIC ANALYSIS, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, DATA ANALYSIS [METHODS], 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, HIGH ANGULAR RESOLUTION [TECHNIQUES], Earth and Planetary Astrophysics (astro-ph.EP), Physics, ADAPTIVE OPTICS, [PHYS]Physics [physics], INDIVIDUAL [STARS], Atmospheric models, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], OPTICAL DATA PROCESSING, Astronomy and Astrophysics, GRAVITATION, Surface gravity, Exoplanet, 13. Climate action, Space and Planetary Science, astro-ph.EP, INDIVIDUAL: 51 ERIDANI [STARS], Astrophysics::Earth and Planetary Astrophysics, SATELLITES, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], STARS, PLANETS, PROBABILITY DISTRIBUTIONS, Astrophysics - Earth and Planetary Astrophysics
Abstract

51 Eridani b is an exoplanet around a young (20 Myr) nearby (29.4 pc) F0-type star, recently discovered by direct imaging. Being only 0.5" away from its host star it is well suited for spectroscopic analysis using integral field spectrographs. We aim to refine the atmospheric properties of this and to further constrain the architecture of the system by searching for additional companions. Using the SPHERE instrument at the VLT we extend the spectral coverage of the planet to the complete Y- to H-band range and provide photometry in the K12-bands (2.11, 2.25 micron). The object is compared to other cool and peculiar dwarfs. Furthermore, the posterior probability distributions of cloudy and clear atmospheric models are explored using MCMC. We verified our methods by determining atmospheric parameters for the two benchmark brown dwarfs Gl 570D and HD 3651B. For probing the innermost region for additional companions, archival VLT-NACO (L') SAM data is used. We present the first spectrophotometric measurements in the Y- and K-bands for the planet and revise its J-band flux to values 40% fainter than previous measurements. Cloudy models with uniform cloud coverage provide a good match to the data. We derive the temperature, radius, surface gravity, metallicity and cloud sedimentation parameter f_sed. We find that the atmosphere is highly super-solar (Fe/H~1.0) with an extended, thick cloud cover of small particles. The model radius and surface gravity suggest planetary masses of about 9 M_jup. The evolutionary model only provides a lower mass limit of >2 M_jup (for pure hot-start). The cold-start model cannot explain the planet's luminosity. The SPHERE and NACO/SAM detection limits probe the 51 Eri system at Solar System scales and exclude brown-dwarf companions more massive than 20 M_jup beyond separations of ~2.5 au and giant planets more massive than 2 M_jup beyond 9 au., 29 pages, 31 figures, accepted for publication in A&A

Published
2017
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12. First Scattered-light Images of the Gas-rich Debris Disk around 49 Ceti

Author

C. H. Chen, A. Boccaletti, Abhijith Rajan, C. del Burgo, Dimitri Mawet, J. C. Augereau, Anne-Marie Lagrange, Christophe Pinte, Julien Milli, Steve Ertel, Elena Gofas-Salas, S. Wolff, J. B. Hagan, Aki Roberge, Dean C. Hines, Mamadou N'Diaye, Rémi Soummer, M. D. Perrin, Z. Wahhaj, David A. Golimowski, Olivier Absil, W. R. F. Dent, Elodie Choquet, Julien Girard, P. Hibon, Glenn Schneider, Mark Booth, David Mouillet, Mark C. Wyatt, Luca Matrà, Laurent Pueyo, Grant M. Kennedy, John H. Debes, C. A. Gomez Gonzalez, Jet Propulsion Laboratory (JPL), California Institute of Technology (CALTECH)-NASA, European Southern Observatory [Santiago] (ESO), European Southern Observatory (ESO), Space Telescope Science Institute (STSci), Exoplanets and Stellar Astrophysics Lab, NASA Goddard Space Flight Center (GSFC), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-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 Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-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 Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Astrophysikalisches Institut und Universitätssternwarte, Pontificia Universidad Católica de Chile (UC), Space Sciences, Technologies and Astrophysics Research Institute (STAR), Université de Liège, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE), Atacama Large Millimeter/submillimeter Array (ALMA), Steward Observatory, University of Arizona, DOTA, ONERA, Université Paris Saclay [Palaiseau], ONERA-Université Paris-Saclay, Institute of Astronomy [Cambridge], University of Cambridge [UK] (CAM), Caltech Department of Astronomy [Pasadena], California Institute of Technology (CALTECH), Université Côte d'Azur (UCA), Arizona State University [Tempe] (ASU), Johns Hopkins University (JHU), NASA-California Institute of Technology (CALTECH), GSFC Exoplanets and Stellar Astrophysics Laboratory, 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]), 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), DOTA, ONERA, Université Paris Saclay (COmUE) [Palaiseau], ONERA-Université Paris Saclay (COmUE), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA), Université Paris Saclay (COmUE)-ONERA, Kennedy, Grant [0000-0001-6831-7547], Matr<U+FFFD>, Luca [0000-0003-4705-3188], Wyatt, Mark [0000-0001-9064-5598], and Apollo - University of Cambridge Repository

Subjects
010504 meteorology & atmospheric sciences, FOS: Physical sciences, CIRCUMSTELLAR MATTER, Astrophysics, 01 natural sciences, 0103 physical sciences, TECHNIQUES: IMAGE PROCESSING, Angular resolution, Absorption (electromagnetic radiation), 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Earth and Planetary Astrophysics (astro-ph.EP), Physics, [PHYS]Physics [physics], Debris disk, Infrared excess, Very Large Telescope, Scattering, Astronomy and Astrophysics, stars: individual (49 Ceti), Debris, [PHYS.PHYS.PHYS-SPACE-PH]Physics [physics]/Physics [physics]/Space Physics [physics.space-ph], 13. Climate action, Space and Planetary Science, [SPI.OPTI]Engineering Sciences [physics]/Optics / Photonic, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], STAR : INDIVUDAL (49 CETI), Main sequence, Astrophysics - Earth and Planetary Astrophysics
Abstract

We present the first scattered-light images of the debris disk around 49 ceti, a ~40 Myr A1 main sequence star at 59 pc, famous for hosting two massive dust belts as well as large quantities of atomic and molecular gas. The outer disk is revealed in reprocessed archival Hubble Space Telescope NICMOS F110W images, as well as new coronagraphic H band images from the Very Large Telescope SPHERE instrument. The disk extends from 1.1" (65 AU) to 4.6" (250 AU), and is seen at an inclination of 73degr, which refines previous measurements at lower angular resolution. We also report no companion detection larger than 3 M_Jup at projected separations beyond 20 AU from the star (0.34"). Comparison between the F110W and H-band images is consistent with a grey color of 49 ceti's dust, indicating grains larger than >2microns. Our photometric measurements indicate a scattering efficiency / infrared excess ratio of 0.2-0.4, relatively low compared to other characterized debris disks. We find that 49 ceti presents morphological and scattering properties very similar to the gas-rich HD 131835 system. From our constraint on the disk inclination we find that the atomic gas previously detected in absorption must extend to the inner disk, and that the latter must be depleted of CO gas. Building on previous studies, we propose a schematic view of the system describing the dust and gas structure around 49 ceti and hypothetic scenarios for the gas nature and origin., Accepted for publication in ApJL. 7 pages, 4 figures

Published
2017
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13. First light of the VLT planet finder SPHERE I. Detection and characterization of the substellar companion GJ 758 B

Author

A. Vigan, M. Bonnefoy, C. Ginski, H. Beust, R. Galicher, M. Janson, J.-L. Baudino, E. Buenzli, J. Hagelberg, V. D’Orazi, S. Desidera, A.-L. Maire, R. Gratton, J.-F. Sauvage, G. Chauvin, C. Thalmann, L. Malo, G. Salter, A. Zurlo, J. Antichi, A. Baruffolo, P. Baudoz, P. Blanchard, A. Boccaletti, J.-L. Beuzit, M. Carle, R. Claudi, A. Costille, A. Delboulbé, K. Dohlen, C. Dominik, M. Feldt, T. Fusco, L. Gluck, J. Girard, E. Giro, C. Gry, T. Henning, N. Hubin, E. Hugot, M. Jaquet, M. Kasper, A.-M. Lagrange, M. Langlois, D. Le Mignant, M. Llored, F. Madec, P. Martinez, D. Mawet, D. Mesa, J. Milli, D. Mouillet, T. Moulin, C. Moutou, A. Origné, A. Pavlov, D. Perret, C. Petit, J. Pragt, P. Puget, P. Rabou, S. Rochat, R. Roelfsema, B. Salasnich, H.-M. Schmid, A. Sevin, R. Siebenmorgen, A. Smette, E. Stadler, M. Suarez, M. Turatto, S. Udry, F. Vakili, Z. Wahhaj, L. Weber, F. Wildi, 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), European Southern Observatory [Santiago] (ESO), European Southern Observatory (ESO), 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]), Leiden Observatory [Leiden], Universiteit Leiden, 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), Stockholm University, Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Institute for Astronomy [Honolulu], University of Hawai‘i [Mānoa] (UHM), Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève = University of Geneva (UNIGE), INAF - Osservatorio Astronomico di Padova (OAPD), Istituto Nazionale di Astrofisica (INAF), Macquarie University, Monash University [Melbourne], DOTA, ONERA, Université Paris Saclay (COmUE) [Châtillon], ONERA-Université Paris Saclay (COmUE), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), CFHT, Universidad Diego Portales [Santiago] (UDP), Universidad de Santiago de Chile [Santiago] (USACH), INAF - Osservatorio Astrofisico di Arcetri (OAA), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Centre de Physique des Particules de Marseille (CPPM), Aix Marseille Université (AMU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche Astrophysique de Lyon (CRAL), 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), Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Observatoire de la Côte d'Azur (OCA), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), California Institute of Technology (CALTECH), De la Molécule aux Nanos-objets : Réactivité, Interactions et Spectroscopies (MONARIS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), NOVA Optical Infrared Instrumentation Group, Institut d'Astrophysique et de Géophysique [Liège], Université de Liège, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), European Synchrotron Radiation Facility (ESRF), Centre de Recherche en Acquisition et Traitement de l'Image pour la Santé (CREATIS), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Jean Monnet - Saint-Étienne (UJM)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Low Energy Astrophysics (API, FNWI), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-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 Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-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 Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden [Leiden], Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Université de Genève (UNIGE), DOTA, ONERA, Université Paris Saclay [Châtillon], ONERA-Université Paris-Saclay, Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology in Zürich [Zürich] (ETH Zürich), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Aix Marseille Université (AMU), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), UMR 5805 Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Université Jean Monnet [Saint-Étienne] (UJM)-Hospices Civils de Lyon (HCL)-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Santé et de la Recherche Médicale (INSERM), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Institut de Chimie du CNRS (INC)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), and Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Physics, Proper motion, 010308 nuclear & particles physics, Monte Carlo method, Brown dwarf, FOS: Physical sciences, Astronomy and Astrophysics, Markov chain Monte Carlo, Astrophysics, Astrometry, First light, 01 natural sciences, Photometry (optics), symbols.namesake, 13. Climate action, Space and Planetary Science, Planet, 0103 physical sciences, symbols, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

GJ758 B is a brown dwarf companion to a nearby (15.76 pc) solar-type, metal-rich (M/H = +0.2 dex) main-sequence star (G9V) that was discovered with Subaru/HiCIAO in 2009. From previous studies, it has drawn attention as being the coldest (~600K) companion ever directly imaged around a neighboring star. We present new high-contrast data obtained during the commissioning of the SPHERE instrument at the VLT. The data was obtained in Y-, J-, H-, and Ks-bands with the dual-band imaging (DBI) mode of IRDIS, providing a broad coverage of the full near-infrared (near-IR) range at higher contrast and better spectral sampling than previously reported. In this new set of high-quality data, we report the re-detection of the companion, as well as the first detection of a new candidate closer-in to the star. We use the new 8 photometric points for an extended comparison of GJ758 B with empirical objects and 4 families of atmospheric models. From comparison to empirical object, we estimate a T8 spectral type, but none of the comparison object can accurately represent the observed near-IR fluxes of GJ758 B. From comparison to atmospheric models, we attribute a Teff = 600K $\pm$ 100K, but we find that no atmospheric model can adequately fit all the fluxes of GJ758 B. The photometry of the new candidate companion is broadly consistent with L-type objects, but a second epoch with improved photometry is necessary to clarify its status. The new astrometry of GJ758 B shows a significant proper motion since the last epoch. We use this result to improve the determination of the orbital characteristics using two fitting approaches, Least-Square Monte Carlo and Markov Chain Monte Carlo. Finally, we analyze the sensitivity of our data to additional closer-in companions and reject the possibility of other massive brown dwarf companions down to 4-5 AU. [abridged], 20 pages, 15 figures. Accepted for publication in A&A

Published
2016
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14. TheSpitzerc2d Survey of Large, Nearby, Interstellar Clouds. I. Chamaeleon II Observed with MIPS

Author

D. L. Padgett, Phil Myers, Tyler L. Bourke, Shih-Ping Lai, Anandi Salinas, A. I. Sargent, William Spiesman, Z. Wahhaj, Frank Bertoldi, David W. Koerner, Jens Kauffmann, G. A. Blake, K. E. Young, J. M. Alcalá, Lori Allen, T. Y. Brooke, E. F. van Dishoeck, Paul M. Harvey, Peter Teuben, Nicholas Chapman, Lee G. Mundy, K. R. Stapelfeldt, and Neal J. Evans

Subjects
Physics, Astrophysics (astro-ph), Interstellar cloud, FOS: Physical sciences, Astronomy and Astrophysics, Photometer, Astrophysics, law.invention, Telescope, Spitzer Space Telescope, Space and Planetary Science, law, Chamaeleon, Millimeter, Data reduction
Abstract

We present maps of over 1.5 square degrees in Chamaeleon (Cha) II at 24, 70, and 160 micron observed with the Spitzer Space Telescope Multiband Imaging Photometer for Spitzer (MIPS) and a 1.2 square degree millimeter map from SIMBA on the Swedish-ESO Submillimetre Telescope (SEST). The c2d Spitzer Legacy Team's data reduction pipeline is described in detail. Over 1500 24 micron sources and 41 70 micron sources were detected by MIPS with fluxes greater than 10-sigma. More than 40 potential YSOs are identified with a MIPS and 2MASS color-color diagram and by their spectral indices, including two previously unknown sources with 24 micron excesses. Our new SIMBA millimeter map of Cha II shows that only a small fraction of the gas is in compact structures with high column densities. The extended emission seen by MIPS is compared with previous CO observations. Some selected interesting sources, including two detected at 1 mm, associated with Cha II are discussed in detail and their SEDs presented. The classification of these sources using MIPS data is found to be consistent with previous studies., Comment: 44 pages, 12 figures (1 color), to be published in ApJ

Published
2005
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15. The Gemini NICI Planet-Finding Campaign

Author

Z. Wahhaj, Beth Biller, Evgenya L. Shkolnik, É. Artigau, Markus Hartung, Michael C. Liu, Eric L. Nielsen, D. Toomey, Laird M. Close, Mark Chun, Christ Ftaclas, and Thomas L. Hayward

Subjects
Physics, Astrophysics::Instrumentation and Methods for Astrophysics, Brown dwarf, Astronomy, Direct imaging, Astrophysics::Cosmology and Extragalactic Astrophysics, Planetary system, Exoplanet, Astrobiology, law.invention, Telescope, Stars, Planet, law, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

Direct imaging is one of the most compelling methods for studying the properties and origins of extrasolar planets. The Near‐Infrared Coronagraphic Imager (NICI) is the new high‐contrast AO imager for the Gemini‐South 8.1‐meter telescope, tailored to direct detection of extrasolar planets through dual‐channel methane‐band coronagraphic imaging. Our team has been selected to carry out an extensive (500 hour) observing program beginning in Winter 2008 to detect and characterize extrasolar planets. We briefly describe the science goals, the Campaign design, NICI on‐sky performance, and a complementary preparatory search for young nearby low‐mass target stars. The Planet‐Finding Campaign is expected to be the largest and most sensitive imaging survey to date for massive (∼1 MJup) planets around other stars.

Published
2009
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16. First light of the VLT planet finder SPHERE. IV. Physical and chemical properties of the planets around HR8799

Author

M. Bonnefoy, A. Zurlo, J. L. Baudino, P. Lucas, D. Mesa, A.-L. Maire, A. Vigan, R. Galicher, D. Homeier, F. Marocco, R. Gratton, G. Chauvin, F. Allard, S. Desidera, M. Kasper, C. Moutou, A.-M. Lagrange, J. Antichi, A. Baruffolo, J. Baudrand, J.-L. Beuzit, A. Boccaletti, F. Cantalloube, M. Carbillet, J. Charton, R. U. Claudi, A. Costille, K. Dohlen, C. Dominik, D. Fantinel, P. Feautrier, M. Feldt, T. Fusco, P. Gigan, J. H. Girard, L. Gluck, C. Gry, T. Henning, M. Janson, M. Langlois, F. Madec, Y. Magnard, D. Maurel, D. Mawet, M. R. Meyer, J. Milli, O. Moeller-Nilsson, D. Mouillet, A. Pavlov, D. Perret, P. Pujet, S. P. Quanz, S. Rochat, G. Rousset, A. Roux, B. Salasnich, G. Salter, J.-F. Sauvage, H. M. Schmid, A. Sevin, C. Soenke, E. Stadler, M. Turatto, S. Udry, F. Vakili, Z. Wahhaj, F. Wildi, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-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 Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-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 Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Universidad Diego Portales [Santiago] (UDP), Millenium Nucleus Protoplanetary Disks in ALMA Early Science, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Centre for Astrophysics Research [Hatfield], University of Hertfordshire [Hatfield] (UH), INAF - Osservatorio Astronomico di Padova (OAPD), Istituto Nazionale di Astrofisica (INAF), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, 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), European Southern Observatory [Santiago] (ESO), European Southern Observatory (ESO), Zentrum für Astronomie der Universität Heidelberg (ZAH), 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-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), ONERA - The French Aerospace Lab [Châtillon], ONERA, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), AlbaNova University Center (ALBANOVA), Stockholm University, California Institute of Technology (CALTECH), Institute of Astronomy [ETH Zürich], Department of Physics [ETH Zürich] (D-PHYS), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology in Zürich [Zürich] (ETH Zürich)-Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology in Zürich [Zürich] (ETH Zürich), Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), 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]), 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), Universität Heidelberg [Heidelberg] = Heidelberg University, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), ONERA-Université Paris Saclay (COmUE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)- Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Université de Genève = University of Geneva (UNIGE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Low Energy Astrophysics (API, FNWI)

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), 010504 meteorology & atmospheric sciences, Atmospheric models, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Metallicity, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, First light, Astrophysics::Cosmology and Extragalactic Astrophysics, Stellar classification, 01 natural sciences, Spectral line, Photometry (astronomy), 13. Climate action, Space and Planetary Science, Planet, 0103 physical sciences, Cloud height, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Astrophysics - Earth and Planetary Astrophysics
Abstract

The system of four planets around HR8799 offers a unique opportunity to probe the physics and chemistry at play in the atmospheres of self-luminous young (~30 Myr) planets. We recently obtained new photometry of the four planets and low-resolution (R~30) spectra of HR8799 d and e with the SPHERE instrument (paper III). In this paper (paper IV), we compare the available spectra and photometry of the planets to known objects and atmospheric models (BT-SETTL14, Cloud-AE60, Exo-REM) to characterize the atmospheric properties of the planets. We find that HR8799d and e properties are well reproduced by those of L6-L8 dusty dwarfs discovered in the field, among which some are candidate members of young nearby associations. No known object reproduces well the properties of planets b and c. Nevertheless, we find that the spectra and WISE photometry of peculiar and/or young early-T dwarfs reddened by submicron grains made of corundum, iron, enstatite, or forsterite successfully reproduce the SED of these two planets. Our analysis confirms that only the Exo-REM models with thick clouds fit (within 2{\sigma}) the whole set of spectrophotometric datapoints available for HR8799 d and e for Teff = 1200 K, log g in the range 3.0-4.5, and M/H=+0.5. The models still fail to reproduce the SED of HR8799c and b. The determination of the metallicity, log g, and cloud thickness are degenerate. We conclude that an enhanced content in dust and decreased CIA of H2 is certainly responsible for the deviation of the properties of the planet with respect to field dwarfs. The analysis suggests in addition that HR8799c and b have later spectral types than the two other planets, and therefore could both have lower masses., Comment: 15 pages, 7 figures, 7 tables, accepted in Astronomy and Astrophysics

Published
2016
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17. Probing the final stages of protoplanetary disk evolution with ALMA

Author

A. Hardy, C. Caceres, M. R. Schreiber, L. Cieza, R. D. Alexander, H. Canovas, J. P. Williams, Z. Wahhaj, and F. Menard

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Physics, Infrared excess, 010308 nuclear & particles physics, Co detection, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Protoplanetary disk, 01 natural sciences, Photoevaporation, Debris, T Tauri star, Stars, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, 0103 physical sciences, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Order of magnitude, Astrophysics - Earth and Planetary Astrophysics
Abstract

The evolution of a circumstellar disk from its gas-rich protoplanetary stage to its gas-poor debris stage is not understood well. It is apparent that disk clearing progresses from the inside-out on a short time scale and models of photoevaporation are frequently used to explain this. However, the photoevaporation rates predicted by models differ by up to two orders of magnitude, resulting in uncertain time scales for the final stages of disk clearing. Photoevaporation theories predict that the final stages of disk-clearing progress in objects that have ceased accretion but still posses considerable material at radii far from the star. Weak-line T Tauri stars (WTTS) with infrared excess are likely in this configuration. We aim to provide observational constraints on theories of disk-clearing by measuring the dust masses and CO content of a sample of young (1.8-26.3 Myr) WTTS. We used ALMA Band 6 to obtain continuum and 12 CO(2-1) line fluxes for a sample of 24 WTTS stars with known infrared excess. We detect continuum emission in only four of 24 WTTS, and no 12 CO(2-1) emission in any. For those WTTS where no continuum was detected, their ages and derived upper limits suggest they are debris disks, which makes them some of the youngest debris disks known. Of those where continuum was detected, three are possible photoevaporating disks, although the lack of CO detection suggests a severely reduced gas-to-dust ratio. The low fraction of continuum detections implies that, once accretion onto the star stops, the clearing of the majority of dust progresses very rapidly. Most WTTS with infrared excess are likely not in transition but are instead young debris disks, whose dust is either primordial and has survived disk-clearing, or is of second-generation origin., submitted to A&A

Published
2015
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18. The Inner Rings of Beta Pictoris

Author

A. I. Sargent, Dana E. Backman, Michael E. Ressler, M. W. Werner, David W. Koerner, and Z. Wahhaj

Subjects
Physics, Long axis, Astrophysics (astro-ph), FOS: Physical sciences, Astronomy and Astrophysics, Radius, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Planetary system, Space and Planetary Science, Beta Pictoris, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics, Dust emission
Abstract

We present Keck images of the dust disk around Beta Pictoris at 17.9 microns that reveal new structure in its morphology. Within 1" (19 AU) of the star, the long axis of the dust emission is rotated by more than 10 degrees with respect to that of the overall disk. This angular offset is more pronounced than the warp detected at 3.5" by HST, and in the opposite direction. By contrast, the long axis of the emission contours at ~ 1.5" from the star is aligned with the HST warp. Emission peaks between 1.5" and 4" from the star hint at the presence of rings similar to those observed in the outer disk at ~ 25" with HST/STIS. A deconvolved image strongly suggests that the newly detected features arise from a system of four non-coplanar rings. Bayesian estimates based on the primary image lead to ring radii of 14+/-1 AU, 28+/-3 AU, 52+/-2 AU and 82+/-2 AU, with orbital inclinations that alternate in orientation relative to the overall disk and decrease in magnitude with increasing radius. We believe these new results make a strong case for the existence of a nascent planetary system around Beta Pic., 5 pages, 2 figures, PDF format. Published in ApJL, December 20,2002

Published
2002

21. Child marriage, climate vulnerability and natural disasters in coastal Bangladesh.

Author

Asadullah MN, Islam KMM, and Wahhaj Z

Subjects
Bangladesh, Child, Climate Change, Female, Floods, Humans, Marriage, Natural Disasters
Abstract

This study examined the nature and correlates of child marriage in eight villages in climate-affected coastal Bangladesh using a mixed-methods approach: focus group discussions and in-depth qualitative interviews of female victims of child marriage as well as quantitative data collected using structured interviews of households. More than two-thirds of the qualitative survey respondents had encountered at least one event of natural disaster before marriage. Quantitative data confirmed significantly higher exposure to flood and river erosion among the coastal population. The quantitative data also suggested a positive association between shocks related to climate events and the incidence of child marriage, while the qualitative data indicated multiple themes related to the causes of child marriage, such as economic vulnerability, coping with risk and patriarchal norms. Yet the qualitative study respondents did not directly refer to natural disasters and climate changes when narrating their marital histories. The qualitative and quantitative evidence does not suggest that dowry-related factors are leading to early marriage. Rather, child marriage appears to be a coping strategy adopted by households in response to their increased vulnerability to natural disasters.

Published
2021
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22. Fast-moving features in the debris disk around AU Microscopii.

Author

Boccaletti A, Thalmann C, Lagrange AM, Janson M, Augereau JC, Schneider G, Milli J, Grady C, Debes J, Langlois M, Mouillet D, Henning T, Dominik C, Maire AL, Beuzit JL, Carson J, Dohlen K, Engler N, Feldt M, Fusco T, Ginski C, Girard JH, Hines D, Kasper M, Mawet D, Ménard F, Meyer MR, Moutou C, Olofsson J, Rodigas T, Sauvage JF, Schlieder J, Schmid HM, Turatto M, Udry S, Vakili F, Vigan A, Wahhaj Z, and Wisniewski J

Abstract

In the 1980s, excess infrared emission was discovered around main-sequence stars; subsequent direct-imaging observations revealed orbiting disks of cold dust to be the source. These 'debris disks' were thought to be by-products of planet formation because they often exhibited morphological and brightness asymmetries that may result from gravitational perturbation by planets. This was proved to be true for the β Pictoris system, in which the known planet generates an observable warp in the disk. The nearby, young, unusually active late-type star AU Microscopii hosts a well-studied edge-on debris disk; earlier observations in the visible and near-infrared found asymmetric localized structures in the form of intensity variations along the midplane of the disk beyond a distance of 20 astronomical units. Here we report high-contrast imaging that reveals a series of five large-scale features in the southeast side of the disk, at projected separations of 10-60 astronomical units, persisting over intervals of 1-4 years. All these features appear to move away from the star at projected speeds of 4-10 kilometres per second, suggesting highly eccentric or unbound trajectories if they are associated with physical entities. The origin, localization, morphology and rapid evolution of these features are difficult to reconcile with current theories.

Published
2015
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23. Legal reform in the presence of a living custom: an economic approach.

Author

Aldashev G, Platteau JP, and Wahhaj Z

Abstract

Empowerment of disadvantaged groups of population is a key issue in development. One major difficulty in implementing progressive legal reforms arises from the persistent and contrary influence of custom. In this paper, we present a simple theoretical framework that analyzes how customary rules evolve under the impact of a change in formal law. This evolution is ultimately caused by a modification of relative costs and benefits of exiting the community by members of the disadvantaged groups as a result of change in the law. We also describe how the welfare of these groups is affected and provide illustrative evidence.

Published
2011
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