A5021566760- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- History and Developments in Astronomy
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Space exploration and regulation
- Isotope Analysis in Ecology
- Astrophysics and Star Formation Studies
- Historical Astronomy and Related Studies
- Planetary Science and Exploration
- Atmospheric Ozone and Climate
- Solar and Space Plasma Dynamics
- Calibration and Measurement Techniques
- Gamma-ray bursts and supernovae
- Adaptive optics and wavefront sensing
- Historical and Architectural Studies
- Astrophysical Phenomena and Observations
- Nuclear Physics and Applications
- Spacecraft and Cryogenic Technologies
- Geophysics and Gravity Measurements
- Space Exploration and Technology
- Global Healthcare and Medical Tourism
- Healthcare Systems and Practices
- Spectroscopy and Laser Applications
- Infrared Target Detection Methodologies
University of Liège
2015-2024
Centre de Recherche en Astronomie Astrophysique et Géophysique
2020
Laboratoire d’Études en Géophysique et Océanographie Spatiales
2003-2017
Max Planck Society
2015
Fund for Scientific Research
1992-2011
European Southern Observatory
2003-2005
University of Maryland, College Park
2005
Pomona College
2005
Netherlands Institute for Radio Astronomy
2005
University of Hawaiʻi at Mānoa
2005
We present a catalogue of 8205 known or suspected Ap, HgMn and Am stars. This paper is major update our first edition the catalog Ap stars includes revised identifications, additional information obtained from literature.
We present new measurements of the mean magnetic field modulus a sample Ap stars with spectral lines resolved into magnetically split components. report discovery 16 having this property. This brings total number such known to 42. have performed more than 750 40 these 42 stars, between May 1988 and August 1995. The best them an estimated accuracy . availability large allows us discuss for first time distribution intensities. A most intriguing result is apparent existence sharp cutoff at low...
TRAPPIST-1 is an ultracool dwarf star transited by seven Earth-sized planets, for which thorough characterization of atmospheric properties, surface conditions encompassing habitability and internal compositions possible with current next generation telescopes. Accurate modeling the essential to achieve this goal. We aim obtain updated stellar parameters TRAPPIST- 1 based on new measurements evolutionary models, compared those used in discovery studies. present a measurement parallax...
High-resolution spectra of the CN B 2 ∑ + – X (0,0) band at 390 nanometers yield isotopic ratios for comets C/1995 O1 (Hale-Bopp) and C/2000 WM1 (LINEAR) as follows: 165 ± 40 115 20 12 C/ 13 C, 140 35 30 14 N/ 15 N. Our N measurements are lower than terrestrial = 272 ratio Hale-Bopp from HCN, presumed parent species CN. This anomaly suggests existence other parent(s) CN, with an even ratio. Organic compounds like those found in interplanetary dust particles good candidates.
Our aim is to determine the isotopic ratios {$^{12}$C/$^{13}$C}{} and {$^{14}$N/$^{15}$N}{} in a variety of comets link these measurements formation evolution solar system. The are measured {for} CN radical by means high-resolution optical spectra R branch B-X (0,0) violet band. {23 from different dynamical classes} have been observed, sometimes at various heliocentric {and nucleocentric} distances, order estimate possible variations parent molecules. remarkably constant (average values of,...
Determination of the nitrogen isotopic ratios in different bodies solar system provides important information regarding system's origin. We unambiguously identified emission lines comets due to 15NH2 radical produced by photodissociation 15NH3. Analysis our data has permitted us measure 14N/15N ratio for a molecule carrying amine (–NH) functional group. This ratio, within error, appears similar that measured HCN and CN radical, lower than protosolar value, suggesting N2 NH3 result from...
Ultraviolet spectra of RR Tel taken with the International Explorer satellite are reported. These cover range 1150–3200 Å at both high and low dispersion through large small apertures. A exposure times yields a dynamic 1000 in line intensities. list 431 lines is presented giving measured wavelength, intensity full width half maximum. Over three-quarters identified. There correlation linewidth ionization energy. Lines identified include common species from once to four ionized. seen generally...
We present here a new robotic telescope called TRAPPIST1 (TRAnsiting Planets and PlanetesImals Small Telescope). Equipped with high-quality CCD camera mounted on 0.6 meter light weight optical tube, TRAPPIST has been installed in April 2010 at the ESO La Silla Observatory (Chile), is now beginning its scientific program. The science goal of study planetary systems through two approaches: detection exoplanets, comets. describe objectives project, hardware, we some first results obtained...
We analyze two multi-chord stellar occultations by Pluto observed on July 18th, 2012 and May 4th, 2013, monitored respectively from five six sites. They provide a total of fifteen light-curves, twelve them being used for simultaneous fit that uses unique temperature profile, assuming clear (no-haze) pure N_2 atmosphere, but allowing possible pressure variation between the dates. find solution fits satisfactorily (i.e. within noise level) all providing atmospheric constraints ~1,190 km...
Two narrow and dense rings (called C1R C2R) were discovered around the Centaur object (10199) Chariklo during a stellar occultation observed on 2013 June 3. Following this discovery, we planned observations of several occultations by Chariklo's system in order to better characterize physical properties ring main body. Here, use 12 successful occulations between 2014 2016. They provide profiles (physical width, opacity, edge structure) constraints radii pole position. Our new are currently...
We present Herschel observations of water isotopologues in the atmosphere Jupiter-family comet 45P/Honda-Mrkos-Pajdusakova. No HDO emission is detected, with a 3 sigma upper limit 2.0 10-4 for D/H ratio. This value consistent earlier measurement 103P/Hartley 2. The canonical measured pre-Herschel sample Oort-cloud comets can be excluded at 4.5 level. presented here further confirm that diversity ratios exists population and emphasize need additional measurements future ground-based...
We present a detailed, extensive investigation of the photometric and spectroscopic behaviour WR 30a. This star is definitely binary system with period around 4.6 d. propose value . The identification components as WO4+O5((f)) indicates massive evolved system; O5 component main-sequence or, more likely, giant star. radial velocities O yield circular orbit an amplitude mass function 0.013 spectrum 30a exhibits strong profile variations broad emission lines that are phase-locked orbital...
Aims.The properties of the early-type stars in core Westerlund 2 cluster are examined order to establish a link between and very massive Wolf-Rayet binary WR 20a as well H ii complex RCW 49.
The 16OH/18OH and OD/OH isotope ratios are measured in the Oort-Cloud comet C/2002 T7 (LINEAR) through ground-based observations of OH ultraviolet bands at 3063 Å (0, 0) 3121 (1, 1) obtained with Very Large Telescope (VLT) feeding Ultraviolet-Visual Echelle Spectrograph (UVES). From ratio, we find 16O/18O = , equal within uncertainties to terrestrial value ratio other comets, although marginally smaller. We also estimate from which derive water. This is compatible water D/H evaluated comets...
The isotopic ratios are diagnostics for the physico-chemical conditions governing molecular formation. In comets, 14N/15N have been measured from HCN in three comets and CN more than 20 comets. Those enriched 15N compared to Sun by a factor of ∼3, small diversity do not depend on dynamical type origin this high 15N-fractionation is still debate because probably comes only HCN, but also other materials (such as polymers or organic dusts) coma. Consequently, an interpretation cometary quite...
We report on observations of comet 9P/Tempel 1 carried out before, during, and after the NASA Deep Impact event (UT July 4), with optical spectrometers UVES HIRES mounted telescopes Kueyen ESO VLT (Chile) Keck I Mauna Kea (Hawaii), respectively. A total observing time about 60 hr, distributed over 15 nights around impact date, allowed us (1) to find a periodic variation 1.709 ± 0.009 days in CN NH flux, explained by presence two major active regions; (2) derive lifetime ≳5 × 104 s (at 1.5...
The ortho-to-para abundance ratio (OPR) of cometary molecules is considered to be one the primordial characteristics ices. We present OPRs ammonia (NH3) in 15 comets based on optical high-dispersion spectroscopic observations NH2, which a photodissociation product gaseous coma. were mainly carried out with VLT/UVES. OPR estimated from NH2 (0, 9, 0) vibronic band. absorption lines by telluric atmosphere are corrected and C2 emission blended removed our analysis. show cluster between 1.1 1.2...
Hyperactive comets are a small group of whose activity higher than expected. They seem to emit more water they should based on the size their nucleus and comet 46P/Wirtanen is one them. Investigating its composition evolution could provide clues about origins formation region in Solar nebulae. Given exceptional close approach 2018 46P Earth, we aim study as function heliocentric distances before after perihelion. We used both TRAPPIST telescopes monitor for almost year with broad-band...
Context. CO is an abundant species in comets, creating + ion with emission lines that can be observed the optical spectral range. A good modeling of its fluorescence spectrum important for a better measurement abundance. Such species, if enough, also used to measure 12 C/ 13 C isotopic ratio. Aims. This study uses opportunity high content comet C/2016 R2 (PanSTARRS), which created bright range, build and test new model this ratio chemical first time ground-based observations. Methods. Thanks...
We observed comet C/1995 O1 (Hale-Bopp) at 4.6–2.9 AU pre-perihelion and 2.8–12.8 post-perihelion with optical long-slit spectroscopy. Emission bands of CN, C3, C2 NH2 have been covered. C3 was detected up to 7.0 AU, CN could be followed 9.8 post-perihelion. Spatial column density profiles the radicals used derive effective parent Haser scale lengths for heliocentric distances beyond 3 AU. Production rates were derived based on these lengths. The observations are in agreement HCN as major...
Context. Westerlund 2 is a young and massive, obscured stellar cluster of our Galaxy. It harbors the most massive star with well-determined parameters, WR20a (82 + 83 ), dozen very early O-type stars (O3–7), wealth PMS stars. Although clear significance, this has not been well-studied.