A. Dias-Oliveira
A5014261107- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Planetary Science and Exploration
- Atmospheric Ozone and Climate
- Astronomical Observations and Instrumentation
- Solar and Space Plasma Dynamics
- Isotope Analysis in Ecology
- Astrophysics and Star Formation Studies
- Geology and Paleoclimatology Research
- Scientific Research and Discoveries
- Space Exploration and Technology
- Calibration and Measurement Techniques
- Astronomy and Astrophysical Research
National Observatory
2012-2019
Laboratório Interinstitucional de e-Astronomia
2019
Laboratório Nacional de Computação Científica
2018
Valongo Observatory
2012-2017
Laboratório Nacional de Astrofísica
2016
Laboratoire d’études spatiales et d’instrumentation en astrophysique
2013-2015
Université de Versailles Saint-Quentin-en-Yvelines
2013-2015
Sorbonne Université
2013-2015
Université Paris Cité
2013-2015
Observatoire de Paris
2013-2015
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,...
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...
We present results derived from four stellar occultations by the plutino object (208996) 2003~AZ$_{84}$, detected at January 8, 2011 (single-chord event), February 3, 2012 (multi-chord), December 2, 2013 (single-chord) and November 15, 2014 (multi-chord). Our observations rule out an oblate spheroid solution for 2003~AZ$_{84}$'s shape. Instead, assuming hydrostatic equilibrium, we find that a Jacobi triaxial with semi axes $(470 \pm 20) \times (383 10) (245 8)$~km % axis ratios $b/a= 0.82...
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$380...
We present results derived from the first multi-chord stellar occultation by trans-Neptunian object (229762) 2007 UK$_{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...
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 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...
The irregular satellites of the giant planets are believed to have been captured during evolution solar system. Knowing their physical parameters, such as size, density, and albedo is important for constraining where they came from how were captured. best way obtain these parameters observations in situ by spacecrafts or stellar occultations objects. Both techniques demand that orbits well known. We aimed good astrometric positions improve ephemeris. identified reduced several three...
Context. We study trans-Neptunian objects (TNOs) from stellar occultations.
During the 2014–2015 mutual events season, Institut de Mécanique Céleste et Calcul des Éphémérides (IMCCE), Paris, France, and Sternberg Astronomical Institute (SAI), Moscow, Russia, led an international observation campaign to record ground-based photometric observations of Galilean moon occultations eclipses. We focused on processing complete data base compute new accurate astrometric positions. used our method derive positions from light curves events. developed model eclipses, while...
Typically we can deliver astrometric positions of natural satellites with errors in the 50–150 mas range. Apparent distances from mutual phenomena, have much smaller errors, less than 10 mas. However, this method only be applied during equinox planets. We developed a that provide accurate data for – approximations. The when any two pass close by each other apparent sky plane. fundamental parameter is central instant t0 passage reach minimum. Galilean moons. All observations were made 0.6 m...
Context . From 1988 to 2016, several stellar occultations have been observed characterise Pluto’s atmosphere and its evolution. each occultation, an accurate astrometric position of Pluto at the observation epoch is derived. These positions mainly depend on occulted star precision timing. Aims We present 19 derived from 2016. Using Gaia DR2 for stars, accuracy these estimated 2−10 mas, depending circumstances. positions, we derive updated ephemeris system barycentre using NIMA code. Methods...
The light curves of mutual eclipses and occultations between the natural satellites a planet allow us to obtain high-precision position relative motion from differential photometry, enough detect weak orbital disturbing forces, such as tidal forces. observations are made during equinoxes planet.
The technique of mutual approximations accurately gives the central instant maximum apparent approximation two moving natural satellites in plane sky. This can be used ephemeris fitting to infer relative positions with high precision. Only phenomena – occultations and eclipses achieve better results. However, only occur every six years case Jupiter. Mutual do not have this restriction observed at any time year as long are visible. In work, we present 104 instants determined from observations...
We determine accurate positions of the main satellites Uranus: Miranda, Ariel, Umbriel, Titania, and Oberon. Positions Uranus, as derived from those these satellites, are also determined. The observational period spans 1992 to 2011. All runs were made at Pico dos Dias Observatory, Brazil. used software called Platform for Reduction Astronomical Images Automatically (PRAIA) minimise (digital coronography) influence scattered light Uranus on astrometric measurements satellites. then indirectly...
Context. The photometry of mutual occultations and eclipses natural planetary satellites can be used to infer very accurate astrometric data. This achieved by processing the light curves observed during international campaigns photometric observations these events.