References of "Reggiani, Maddalena"      in Complete repository Arts & humanities   Archaeology   Art & art history   Classical & oriental studies   History   Languages & linguistics   Literature   Performing arts   Philosophy & ethics   Religion & theology   Multidisciplinary, general & others Business & economic sciences   Accounting & auditing   Production, distribution & supply chain management   Finance   General management & organizational theory   Human resources management   Management information systems   Marketing   Strategy & innovation   Quantitative methods in economics & management   General economics & history of economic thought   International economics   Macroeconomics & monetary economics   Microeconomics   Economic systems & public economics   Social economics   Special economic topics (health, labor, transportation…)   Multidisciplinary, general & others Engineering, computing & technology   Aerospace & aeronautics engineering   Architecture   Chemical engineering   Civil engineering   Computer science   Electrical & electronics engineering   Energy   Geological, petroleum & mining engineering   Materials science & engineering   Mechanical engineering   Multidisciplinary, general & others Human health sciences   Alternative medicine   Anesthesia & intensive care   Cardiovascular & respiratory systems   Dentistry & oral medicine   Dermatology   Endocrinology, metabolism & nutrition   Forensic medicine   Gastroenterology & hepatology   General & internal medicine   Geriatrics   Hematology   Immunology & infectious disease   Laboratory medicine & medical technology   Neurology   Oncology   Ophthalmology   Orthopedics, rehabilitation & sports medicine   Otolaryngology   Pediatrics   Pharmacy, pharmacology & toxicology   Psychiatry   Public health, health care sciences & services   Radiology, nuclear medicine & imaging   Reproductive medicine (gynecology, andrology, obstetrics)   Rheumatology   Surgery   Urology & nephrology   Multidisciplinary, general & others Law, criminology & political science   Civil law   Criminal law & procedure   Criminology   Economic & commercial law   European & international law   Judicial law   Metalaw, Roman law, history of law & comparative law   Political science, public administration & international relations   Public law   Social law   Tax law   Multidisciplinary, general & others Life sciences   Agriculture & agronomy   Anatomy (cytology, histology, embryology...) & physiology   Animal production & animal husbandry   Aquatic sciences & oceanology   Biochemistry, biophysics & molecular biology   Biotechnology   Entomology & pest control   Environmental sciences & ecology   Food science   Genetics & genetic processes   Microbiology   Phytobiology (plant sciences, forestry, mycology...)   Veterinary medicine & animal health   Zoology   Multidisciplinary, general & others Physical, chemical, mathematical & earth Sciences   Chemistry   Earth sciences & physical geography   Mathematics   Physics   Space science, astronomy & astrophysics   Multidisciplinary, general & others Social & behavioral sciences, psychology   Animal psychology, ethology & psychobiology   Anthropology   Communication & mass media   Education & instruction   Human geography & demography   Library & information sciences   Neurosciences & behavior   Regional & inter-regional studies   Social work & social policy   Sociology & social sciences   Social, industrial & organizational psychology   Theoretical & cognitive psychology   Treatment & clinical psychology   Multidisciplinary, general & others     Showing results 1 to 20 of 32 1 2     Discovery of a point-like source and a third spiral arm in the transition disk around the Herbig Ae star MWC 758Reggiani, Maddalena ; Christiaens, V.; Absil, Olivier et alin Astronomy and Astrophysics (in press)Transition disks offer the extraordinary opportunity to look for newly born planets and investigate the early stages of planet formation. In this context we observed the Herbig A5 star MWC 758 with the L ... [more ▼]Transition disks offer the extraordinary opportunity to look for newly born planets and investigate the early stages of planet formation. In this context we observed the Herbig A5 star MWC 758 with the L band vector vortex coronagraph installed in the near-infrared camera and spectrograph NIRC2 at the Keck II telescope, with the aim of unveiling the nature of the spiral structure by constraining the presence of planetary companions in the system. Our high-contrast imaging observations show a bright (delta L=7.0+/-0.3 mag) point-like emission, south of MWC 758 at a deprojected separation of about 20 au (r=0.111+/- 0. 004 arcsec) from the central star. We also recover the two spiral arms (south-east and north-west), already imaged by previous studies in polarized light, and discover a third one to the south-west of the star. No additional companions were detected in the system down to 5 Jupiter masses beyond 0.6 arcsec from the star. We propose that the bright L band emission could be caused by the presence of an embedded and accreting protoplanet, although the possibility of it being an asymmetric disk feature cannot be excluded. The spiral structure is probably not related to the protoplanet candidate, unless on an inclined and eccentric orbit, and it could be due to one (or more) yet undetected planetary companions at the edge of or outside the spiral pattern. Future observations and additional simulations will be needed to shed light on the true nature of the point-like source and its link with the spiral arms. [less ▲]Detailed reference viewed: 12 (0 ULiège) The path towards high-contrast imaging with the VLTI: the Hi-5 projectDefrere, Denis ; Absil, Olivier ; Berger, J.-P. et alin Experimental Astronomy: Astrophysical Instrumentation and Methods (in press), 1801The development of high-contrast capabilities has long been recognized as one of the top priorities for the VLTI. As of today, the VLTI routinely achieves contrasts of a few 10$^{-3}$ in the near-infrared ... [more ▼]The development of high-contrast capabilities has long been recognized as one of the top priorities for the VLTI. As of today, the VLTI routinely achieves contrasts of a few 10$^{-3}$ in the near-infrared with PIONIER (H band) and GRAVITY (K band). Nulling interferometers in the northern hemisphere and non-redundant aperture masking experiments have, however, demonstrated that contrasts of at least a few 10$^{-4}$ are within reach using specific beam combination and data acquisition techniques. In this paper, we explore the possibility to reach similar or higher contrasts on the VLTI. After reviewing the state-of-the-art in high-contrast infrared interferometry, we discuss key features that made the success of other high-contrast interferometric instruments (e.g., integrated optics, nulling, closure phase, and statistical data reduction) and address possible avenues to improve the contrast of the VLTI by at least one order of magnitude. In particular, we discuss the possibility to use integrated optics, proven in the near-infrared, in the thermal near-infrared (L and M bands, 3-5 $\mu$m), a sweet spot to image and characterize young extra-solar planetary systems. Finally, we address the science cases of a high-contrast VLTI imaging instrument and focus particularly on exoplanet science (young exoplanets, planet formation, and exozodiacal disks), stellar physics (fundamental parameters and multiplicity), and extragalactic astrophysics (active galactic nuclei and fundamental constants). Synergies and scientific preparation for other potential future instruments such as the Planet Formation Imager are also briefly discussed. [less ▲]Detailed reference viewed: 8 (0 ULiège) Search for young planets in transition disks: investigating the early phases of planet formation with the Keck/NIRC2 vortex coronagraph.Reggiani, Maddalena Conference (2017, December 12)Detailed reference viewed: 16 (3 ULiège) A candidate accreting protoplanet in the transition disk around MWC 758Reggiani, Maddalena Scientific conference (2017, September 19)Detailed reference viewed: 8 (0 ULiège) Direct imaging constraints on planetary companions in the transition disk around MWC 758Reggiani, Maddalena Conference (2017, August 23)Detailed reference viewed: 6 (0 ULiège) M Dwarf Exoplanet Surface Density Distribution: A Log-Normal Fit from 0.07-400 AUMeyer, Michael R.; Amara, Adam; Reggiani, Maddalena et alin Astronomy and Astrophysics (2017), 1707We fit a log-normal function to the M dwarf orbital surface density distribution of gas giant planets, over the mass range 1-10 times that of Jupiter, from 0.07-400 AU. We use a Markov Chain Monte Carlo ... [more ▼]We fit a log-normal function to the M dwarf orbital surface density distribution of gas giant planets, over the mass range 1-10 times that of Jupiter, from 0.07-400 AU. We use a Markov Chain Monte Carlo approach to explore the likelihoods of various parameter values consistent with point estimates of the data given our assumed functional form. This fit is consistent with radial velocity, microlensing, and direct imaging observations, is well-motivated from theoretical and phenomenological viewpoints, and makes predictions of future surveys. We present probability distributions for each parameter as well as a Maximum Likelihood Estimate solution. We suggest this function makes more physical sense than other widely used functions, and explore the implications of our results on the design of future exoplanet surveys. [less ▲]Detailed reference viewed: 19 (4 ULiège) The VLT/NaCo large program to probe the occurrence of exoplanets and brown dwarfs at wide orbits. IV. Gravitational instability rarely forms wide, giant planetsVigan, A.; Bonavita, M.; Biller, B. et alin Astronomy and Astrophysics (2017), 603Understanding the formation and evolution of giant planets (≥1 M[SUB]Jup[/SUB]) at wide orbital separation (≥5 AU) is one of the goals of direct imaging. Over the past 15 yr, many surveys have placed ... [more ▼]Understanding the formation and evolution of giant planets (≥1 M[SUB]Jup[/SUB]) at wide orbital separation (≥5 AU) is one of the goals of direct imaging. Over the past 15 yr, many surveys have placed strong constraints on the occurrence rate of wide-orbit giants, mostly based on non-detections, but very few have tried to make a direct link with planet formation theories. In the present work, we combine the results of our previously published VLT/NaCo large program with the results of 12 past imaging surveys to constitute a statistical sample of 199 FGK stars within 100 pc, including three stars with sub-stellar companions. Using Monte Carlo simulations and assuming linear flat distributions for the mass and semi-major axis of planets, we estimate the sub-stellar companion frequency to be within 0.75-5.70% at the 68% confidence level (CL) within 20-300 AU and 0.5-75 M[SUB]Jup[/SUB], which is compatible with previously published results. We also compare our results with the predictions of state-of-the-art population synthesis models based on the gravitational instability (GI) formation scenario with and without scattering. We estimate that in both the scattered and non-scattered populations, we would be able to detect more than 30% of companions in the 1-75 M[SUB]Jup[/SUB] range (95% CL). With the threesub-stellar detections in our sample, we estimate the fraction of stars that host a planetary system formed by GI to be within 1.0-8.6% (95% CL). We also conclude that even though GI is not common, it predicts a mass distribution of wide-orbit massive companions that is much closer to what is observed than what the core accretion scenario predicts. Finally, we associate the present paper with the release of the Direct Imaging Virtual Archive (DIVA), a public database that aims at gathering the results of past, present, and future direct imaging surveys. Based on observations collected at the European Southern Observatory, Chile (ESO Large Program 184.C-0157 and Open Time 089.C-0137A and 090.C-0252A). [less ▲]Detailed reference viewed: 34 (4 ULiège) The W. M. Keck Observatory infrared vortex coronagraph and a first image of HIP79124 BSerabyn, Eugene; Huby, Elsa ; Matthews, Keith et alin Astronomical Journal (The) (2017), 153(1), 43An optical vortex coronagraph has been implemented within the NIRC2 camera on the Keck II telescope and used to carry out on-sky tests and observations. The development of this new L'-band observational ... [more ▼]An optical vortex coronagraph has been implemented within the NIRC2 camera on the Keck II telescope and used to carry out on-sky tests and observations. The development of this new L'-band observational mode is described, and an initial demonstration of the new capability is presented: a resolved image of the low-mass companion to HIP79124, which had previously been detected by means of interferometry. With HIP79124 B at a projected separation of 186.5 mas, both the small inner working angle of the vortex coronagraph and the related imaging improvements were crucial in imaging this close companion directly. Due to higher Strehl ratios and more relaxed contrasts in L' band versus H band, this new coronagraphic capability will enable high-contrast small-angle observations of nearby young exoplanets and disks on a par with those of shorter-wavelength extreme adaptive optics coronagraphs. [less ▲]Detailed reference viewed: 65 (11 ULiège) Characterization of the inner disk around HD 141569 A from Keck/NIRC2 L-band vortex coronagraphyMawet, Dimitri; Choquet, Élodie; Absil, Olivier et alin Astronomical Journal (The) (2017), 153(1), 44HD 141569 A is a pre-main sequence B9.5 Ve star surrounded by a prominent and complex circumstellar disk, likely still in a transition stage from protoplanetary to debris disk phase. Here, we present a ... [more ▼]HD 141569 A is a pre-main sequence B9.5 Ve star surrounded by a prominent and complex circumstellar disk, likely still in a transition stage from protoplanetary to debris disk phase. Here, we present a new image of the third inner disk component of HD 141569 A made in the L' band (3.8 micron) during the commissioning of the vector vortex coronagraph recently installed in the near-infrared imager and spectrograph NIRC2 behind the W.M. Keck Observatory Keck II adaptive optics system. We used reference point spread function subtraction, which reveals the innermost disk component from the inner working distance of $\simeq 23$ AU and up to $\simeq 70$ AU. The spatial scale of our detection roughly corresponds to the optical and near-infrared scattered light, thermal Q, N and 8.6 micron PAH emission reported earlier. We also see an outward progression in dust location from the L'-band to the H-band (VLT/SPHERE image) to the visible (HST/STIS image), likely indicative of dust blowout. The warm disk component is nested deep inside the two outer belts imaged by HST NICMOS in 1999 (respectively at 406 and 245 AU). We fit our new L'-band image and spectral energy distribution of HD 141569 A with the radiative transfer code MCFOST. Our best-fit models favor pure olivine grains, and are consistent with the composition of the outer belts. While our image shows a putative very-faint point-like clump or source embedded in the inner disk, we did not detect any true companion within the gap between the inner disk and the first outer ring, at a sensitivity of a few Jupiter masses. [less ▲]Detailed reference viewed: 61 (11 ULiège) Commissioning and first light results of an L'-band vortex coronagraph with the Keck II adaptive optics NIRC2 science instrumentFemenía Castellá, Bruno; Serabyn, Eugene; Mawet, Dimitri et alin Marchetti, E.; Close, L.; Véran, J.-P. (Eds.) Adaptive Optics Systems V (2016, July 26)On March 2015 an L'-band vortex coronagraph based on an Annular Groove Phase Mask made up of a diamond sub-wavelength grating was installed on NIRC2 as a demonstration project. This vortex coronagraph ... [more ▼]On March 2015 an L'-band vortex coronagraph based on an Annular Groove Phase Mask made up of a diamond sub-wavelength grating was installed on NIRC2 as a demonstration project. This vortex coronagraph operates in the L' band not only in order to take advantage from the favorable star/planet contrast ratio when observing beyond the K band, but also to exploit the fact that the Keck II Adaptive Optics (AO) system delivers nearly extreme adaptive optics image quality (Strehl ratios values near 90%) at 3.7μm. We describe the hardware installation of the vortex phase mask during a routine NIRC2 service mission. The success of the project depends on extensive software development which has allowed the achievement of exquisite real-time pointing control as well as further contrast improvements by using speckle nulling to mitigate the effect of static speckles. First light of the new coronagraphic mode was on June 2015 with already very good initial results. Subsequent commissioning nights were interlaced with science nights by members of the VORTEX team with their respective scientific programs. The new capability and excellent results so far have motivated the VORTEX team and the Keck Science Steering Committee (KSSC) to offer the new mode in shared risk mode for 2016B. [less ▲]Detailed reference viewed: 28 (3 ULiège) Three years of harvest with the vector vortex coronagraph in the thermal infraredAbsil, Olivier ; Mawet, D.; Karlsson, M. et alin Evans, C.; Simard, L.; Takami, H. (Eds.) Ground-based and Airborne Instrumentation for Astronomy VI (2016, June 26)For several years, we have been developing vortex phase masks based on sub-wavelength gratings, known as Annular Groove Phase Masks. Etched onto diamond substrates, these AGPMs are currently designed to ... [more ▼]For several years, we have been developing vortex phase masks based on sub-wavelength gratings, known as Annular Groove Phase Masks. Etched onto diamond substrates, these AGPMs are currently designed to be used in the thermal infrared (ranging from 3 to 13 μm). Our AGPMs were first installed on VLT/NACO and VLT/VISIR in 2012, followed by LBT/LMIRCam in 2013 and Keck/NIRC2 in 2015. In this paper, we review the development, commissioning, on-sky performance, and early scientific results of these new coronagraphic modes and report on the lessons learned. We conclude with perspectives for future developments and applications. [less ▲]Detailed reference viewed: 48 (23 ULiège) The VLT/NaCo large program to probe the occurrence of exoplanets and brown dwarfs at wide orbits . III. The frequency of brown dwarfs and giant planets as companions to solar-type starsReggiani, Maddalena ; Meyer, M. R.; Chauvin, G. et alin Astronomy and Astrophysics (2016), 586Context. In recent years there have been many attempts to characterize the occurrence and distribution of stellar, brown dwarf (BD), and planetary-mass companions to solar-type stars with the aim of ... [more ▼]Context. In recent years there have been many attempts to characterize the occurrence and distribution of stellar, brown dwarf (BD), and planetary-mass companions to solar-type stars with the aim of constraining formation mechanisms. From radial velocity observations a dearth of companions with masses between 10-40 M[SUB]Jupiter[/SUB] has been noticed at close separations, suggesting the possibility of a distinct formation mechanism for objects above and below this range.