R. Vieira-Martins
A5027233461- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Planetary Science and Exploration
- Solar and Space Plasma Dynamics
- Astronomical Observations and Instrumentation
- Atmospheric Ozone and Climate
- Isotope Analysis in Ecology
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Geomagnetism and Paleomagnetism Studies
- Geology and Paleoclimatology Research
- Space Exploration and Technology
- Geological and Geochemical Analysis
- Scientific Research and Discoveries
- Space Satellite Systems and Control
- Calibration and Measurement Techniques
- Astrophysics and Cosmic Phenomena
- Numerical methods for differential equations
- History and Developments in Astronomy
- Mathematics and Applications
- Ionosphere and magnetosphere dynamics
- Quantum chaos and dynamical systems
- Pacific and Southeast Asian Studies
- Control and Dynamics of Mobile Robots
Laboratório Interinstitucional de e-Astronomia
2016-2025
Valongo Observatory
2013-2025
National Observatory
2016-2025
Institut de Mécanique Céleste et de Calcul des Éphémérides
2011-2022
Université Paris Sciences et Lettres
2017-2022
Sorbonne Université
2012-2022
Université de Lille
2012-2022
Centre National de la Recherche Scientifique
2012-2022
Observatoire de Paris
2012-2022
Université Paris Cité
2022
ABSTRACT We present results from a multi-chord Pluto stellar occultation observed on 2015 June 29 New Zealand and Australia. This occurred only two weeks before the NASA Horizons flyby of system serves as useful comparison between ground-based space results. find that Pluto's atmosphere is still expanding, with significant pressure increase 5 ± 2% since 2013 factor almost three 1988. trend rules out, today, an atmospheric collapse associated recession Sun. A central flash, rare occurrence,...
Quaoar is a classical Trans-Neptunian Object (TNO) with an area equivalent diameter of 1,100 km and orbital semi-major axis 43.3 astronomical units. Based on stellar occultations observed between 2018 2021, inhomogeneous ring (Q1R, Quaoar's first ring) was detected around this body. Aims. A new occultation by August 9th, 2022 aiming to improve shape models the physical parameters Q1R while searching for additional material Methods. The provided nine effective chords across Quaoar, pinning...
Abstract The physical and orbital parameters of trans-Neptunian objects provide valuable information about the solar system’s formation evolution. In particular, characterization binaries provides insights into mechanisms that may be playing a role at such large distances from Sun. Studies show two distinct populations, (38628) Huya occupies an intermediate position between unequal-sized those with components roughly equal sizes. this work, we predicted observed three stellar occultation...
Comets offer valuable insights into the early Solar System's conditions and processes. Stellar occultations enable detailed study of cometary nuclei typically hidden by their coma. Observing star's light passing through coma helps infer dust's optical depth near nucleus determine dust opacity detection limits. 29P/Schwassmann-Wachmann 1, a Centaur with diameter approximately 60 km, lies in region transitioning from Centaurs to Jupiter-family comets. Our presents first-ever observed...
We present results derived from the first multi-chord stellar occultations by transneptunian object (50000) Quaoar, observed on 2011 May 4 and 2012 February 17, a single-chord occultation October 15. If timing of five chords obtained in were correct, then Quaoar would possess topographic features (crater or mountain) that be too large for body this mass. An alternative model consists applying time shifts to some account possible errors. Satisfactory elliptical fits are possible, yielding an...
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...
Context. The prediction of stellar occultations by trans-Neptunian objects (TNOs) and Centaurs is a difficult challenge that requires accuracy both in the occulted star position object ephemeris. Until now, most used method prediction, involving dozens TNOs/Centaurs, has been to consider constant offset for right ascension declination with respect reference ephemeris, usually latest public version. This determined as difference between recent observations TNO/Centaur can be successfully...
We use data from five stellar occultations observed between 2013 and 2016 to constrain Chariklo's size shape, the ring reflectivity. consider four possible models for Chariklo (sphere, Maclaurin spheroid, tri-axial ellipsoid Jacobi ellipsoid) we a Bayesian approach estimate corresponding parameters. The spherical model has radius $R=129\pm3$ km. equatorial polar radii $a=b=143^{+3}_{-6}$ km $c=96^{+14}_{-4}$ km, respectively, with density $970^{+300}_{-180}$ kg m$^{-3}$. ellipsoidal semiaxes...
Context. Pluto's tenuous nitrogen (N2) atmosphere undergoes strong seasonal effects due to high obliquity and orbital eccentricity, has been recently (July 2015) observed by the New Horizons spacecraft. Goals are (i) construct a well calibrated record of evolution surface pressure on Pluto (ii) constrain structure lower using central flash in 2015. Method: eleven stellar occultations between 2002 2016 used retrieve atmospheric profiles (density, pressure, temperature) $\sim$5 km $\sim$380...
After the discovery of rings around largest known Centaur object, (10199) Chariklo, we carried out observation campaigns stellar occultations produced by second-largest (2060) Chiron, to better characterize its physical properties and presence material on surroundings. We predicted successfully observed two Chiron. These observations were used constrain size shape fitting elliptical limbs with equivalent surface radii in agreement radiometric measurements. Constraints Chiron are reported for...
We present results derived from the first multi-chord stellar occultation by trans-Neptunian object (229762) 2007 UK$_{126}$, observed on 2014 November 15. The event was Research and Education Collaborative Occultation Network (RECON) project International Timing Association (IOTA) collaborators throughout United States. Use of two different data analysis methods obtain a satisfactory fit to seven chords, yelding an elliptical chords with equatorial radius $R=338_{-10} ^{+15}$ km equivalent...
Trans-Neptunian objects (TNOs) are icy bodies located in the outer solar system that offer key insights into primordial conditions of our planetary system. The stellar occultation technique has proven to be an essential tool for studying these distant and faint objects, enabling precise determinations their size, shape, albedo, while also improving estimates orbital parameters. Among them, (119951) 2002 KX14 is a large classical TNO with limited previous observations unresolved questions...
Abstract We identified known Trans-Neptunian Objects (TNOs) and Centaurs in the complete Dark Energy Survey (DES) year six catalog (DES Y6) through Sky Body Tracker (SkyBoT) tool. classified our dataset of 144 objects into a widely used 4-class taxonomic system TNOs. No such previous classification was available literature for most these objects. From absolute magnitudes average albedos, an estimation diameters all is obtained. Correlations involving colours, orbital parameters, dynamical...
A stellar occultation by Neptune's main satellite, Triton, was observed on 5 October 2017 from Europe, North Africa, and the USA. We derived 90 light curves this event, 42 of which yielded a central flash detection. aimed at constraining Triton's atmospheric structure seasonal variations its pressure since Voyager 2 epoch (1989). also shape lower atmosphere analysis. used Abel inversions direct ray-tracing code to provide density, pressure, temperature profiles in altitude range $\sim$8 km...
Context. In about 2000, the south pole of Triton experienced an extreme summer solstice that occurs every ∼650 years, when subsolar latitude reached 50°S. Bracketing this epoch, a few occultations probed atmosphere in 1989, 1995, 1997, 2008, and 2017. A recent ground-based stellar occultation observed on 6 October 2022 provides new measurement atmospheric pressure Triton. This is presented here. Aims. The goal to constrain volatile transport models (VTMs) atmosphere. basically vapor...
Context. In 2009, the Sun and Earth passed through equatorial plane of Jupiter therefore orbital planes its main satellites. It was equinox on Jupiter. This occurrence made mutual occultations eclipses between satellites possible. Experience has shown that observations such events provide accurate astrometric data able to bring new information dynamics Galilean Observations are under form photometric measurements, but need be organization a worldwide observation campaign maximizing number...
Pluto and its main satellite, Charon, occulted the same star on 2008 June 22. This event was observed from Australia La Réunion Island, providing east north Charon Plutocentric offset in sky plane (J2000): X= + 12,070.5 ± 4 km (+ 546.2 0.2 mas), Y= 4,576.3 24 207.1 1.1 mas) at 19:20:33.82 UT Earth, corresponding to JD 2454640.129964 Pluto. yields Charon's true longitude L= 153.483 0071 satellite orbital (counted ascending node J2000 mean equator) radius r= 19,564 14 that time. We compare...