Publications (61)
The rings of (2060) Chiron: Evidence of an evolving system
C. L. Pereira, F. Braga-Ribas, B. Sicardy +54
The centaur (2060) Chiron has long been a candidate for hosting material in orbit, based on occultation and photometric and spectroscopic data. Here, we present a multichord stella…
The first observed stellar occultations by the irregular satellite (Saturn IX) Phoebe and improved rotational period
A. R. Gomes-Júnior, M. Assafin, F. Braga-Ribas +24
We report six stellar occultations by (Saturn IX) Phoebe, an irregular satellite of Saturn, obtained between mid-2017 and mid-2019. The 2017 July 06 event is the first stellar occu…
Constraints on Triton atmospheric evolution from occultations: 1989-2022
B. Sicardy, A. Tej, A. R. Gomes-Junior +49
Context - Around the year 2000, Triton's south pole experienced an extreme summer solstice that occurs every about 650 years, when the subsolar latitude reached about 50°. Bracket…
Astrometry of mutual approximations between natural satellites. Application to the Galilean moons
B. Morgado, M. Assafin, R. Vieira-Martins +3
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 t…
The trans-Neptunian object (119951) 2002 KX14 revealed via multiple stellar occultations
J. L. Rizos, J. L. Ortiz, F. L. Rommel +55
(119951) 2002 KX14 is a large classical TNO with limited previous observations and unresolved questions regarding its physical properties. Five stellar occultations by 2002 KX14 we…
Astrometric positions for 18 irregular satellites of giant planets from 23 years of observations
A. R. Gomes-Júnior, M. Assafin, R. Vieira-Martins +12
The irregular satellites of the giant planets are believed to have been captured during the evolution of the solar system. Knowing their physical parameters, such as size, density,…
Differential aperture photometry and digital coronagraphy with PRAIA
M. Assafin
PRAIA - Package for the Reduction of Astronomical Images Automatically - is a suite of photometric and astrometric tasks designed to cope with huge amounts of heterogeneous observa…
The changing material around (2060) Chiron from an occultation on 2022 December 15
J. L. Ortiz, C. L. Pereira, B. Sicardy +30
We could accurately predict the shadow path and successfully observe an occultation of a bright star by Chiron on 2022 December 15. The Kottamia Astronomical Observatory in Egypt d…
The large Trans-Neptunian Object 2002 TC from combined stellar occultation, photometry and astrometry data
J. L. Ortiz, P. Santos-Sanz, B. Sicardy +78
On 28th January 2018, the large Trans-Neptunian Object (TNO) 2002TC302 occulted a m15.3 star with ID 130957813463146112 in the Gaia DR2 stellar catalog. 12 positive occultati…
The non-convex shape of (234) Barbara, the first Barbarian
P. Tanga, B. Carry, F. Colas +37
Asteroid (234) Barbara is the prototype of a category of asteroids that has been shown to be extremely rich in refractory inclusions, the oldest material ever found in the Solar Sy…
Results of two multi-chord stellar occultations by dwarf planet (1) Ceres
A. R. Gomes-Júnior, B. L. Giacchini, F. Braga-Ribas +24
We report the results of two multi-chord stellar occultations by the dwarf planet (1) Ceres that were observed from Brazil on 2010 August 17, and from the USA on 2013 October 25. F…
A ring system detected around the Centaur (10199) Chariklo
F. Braga-Ribas, B. Sicardy, J. L. Ortiz +61
Until now, rings have been detected in the Solar System exclusively around the four giant planets. Here we report the discovery of the first minor-body ring system around the Centa…
Pluto's ephemeris from ground-based stellar occultations (1988-2016)
J. Desmars, E. Meza, B. Sicardy +13
From 1988 to 2016, several stellar occultations have been observed to characterize Pluto's atmosphere and its evolution (Meza et al, 2019). From each stellar occultation, an accura…
The multichord stellar occultation by the centaur Bienor on January 11, 2019
E. Fernández-Valenzuela, N. Morales, M. Vara-Lubiano +42
Within our program of physical characterization of trans-Neptunian objects and centaurs, we predicted a stellar occultation by the centaur (54598) Bienor to occur on January 11, 20…
The two rings of (50000) Quaoar
C. L. Pereira, B. Sicardy, B. E. Morgado +66
Quaoar is a classical Trans-Neptunian Object (TNO) with an area equivalent diameter of 1,100 km and an orbital semi-major axis of 43.3 astronomical units. Based on stellar occultat…
A multi-chord stellar occultation by the large trans-Neptunian object (174567) Varda
D. Souami, F. Braga-Ribas, B. Sicardy +41
We present results from the first recorded stellar occultation by the large trans-Neptunian object (174567) Varda that was observed on September 10, 2018. Varda belongs…
On the influence of radio extended structures on offsets between the optical and VLBI positions of sources in the ICRF2
J. I. B. Camargo, A. H. Andrei, M. Assafin +2
Context: To investigate the differences between positions, as determined by optical (direct imaging) and Very Long Baseline Interferometry (VLBI) techniques, of extragalactic sourc…
The size, shape, density and ring of the dwarf planet Haumea from a stellar occultation
J. L. Ortiz, P. Santos-Sanz, B. Sicardy +90
Among the four known transneptunian dwarf planets, Haumea is an exotic, very elongated, and fast rotating body. In contrast to the other dwarf planets, its size, shape, albedo, and…
Kilometer-precise (UII) Umbriel physical properties from the multichord stellar occultation on 2020 September 21
M. Assafin, S. Santos-Filho, B. E. Morgado +39
We report the results of the stellar occultation by (UII) Umbriel on September 21st, 2020. The shadow crossed the USA and Canada, and 19 positive chords were obtained. A limb param…
Constraints on the structure and seasonal variations of Triton's atmosphere from the 5 October 2017 stellar occultation and previous observations
J. Marques Oliveira, B. Sicardy, A. R. Gomes-Júnior +234
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 from this event, 42 of…
Study of the plutino object (208996) 2003 AZ84 from stellar occultations: size, shape and topographic features
A. Dias-Oliveira, B. Sicardy, J. L. Ortiz +60
We present results derived from four stellar occultations by the plutino object (208996) 2003~AZ, detected at January 8, 2011 (single-chord event), February 3, 2012 (multi-c…
First stellar occultation by the Galilean moon Europa and upcoming events between 2019 and 2021
B. Morgado, G. Benedetti-Rossi, A. R. Gomes-Júnior +21
Context. Bright stellar positions are now known with an uncertainty below 1 mas thanks to Gaia DR2. Between 2019-2020, the Galactic plane will be the background of Jupiter. The den…
Refined physical parameters for Chariklo's body and rings from stellar occultations observed between 2013 and 2020
B. E. Morgado, B. Sicardy, F. Braga-Ribas +78
The Centaur (10199) Chariklo has the first rings system discovered around a small object. It was first observed using stellar occultation in 2013. Stellar occultations allow the de…
The Gaia-FUN-SSO observation campaign of 99942 Apophis: A preliminary test for the network
D. Bancelin, W. Thuillot, A. Ivantsov +8
In order to test the coordination and evaluate the overall performance of the Gaia-FUN-SSO, an observation campaign on the Potentially Hazardous Asteroid (99 942) Apophis was condu…
The 2014-2015 Brazilian Mutual Phenomena campaign for the Jovian satellites and improved results for the 2009 events
B. Morgado, R. Vieira-Martins, M. Assafin +15
Progress in astrometry and orbital modelling of planetary moons in the last decade enabled better determinations of their orbits. These studies need accurate positions spread over…
The astrometric Gaia-FUN-SSO observation campaign of 99 942 Apophis
W. Thuillot, D. Bancelin, A. Ivantsov +71
Astrometric observations performed by the Gaia Follow-Up Network for Solar System Objects (Gaia-FUN-SSO) play a key role in ensuring that moving objects first detected by ESA's Gai…
Stellar occultation observations of (38628) Huya and its satellite: a detailed look into the system
F. L. Rommel, E. Fernández-Valenzuela, B. C. N. Proudfoot +78
The physical and orbital parameters of Trans-Neptunian Objects (TNOs) provide valuable information about the Solar System's formation and evolution. In particular, the characteriza…
The 2017 May 20 stellar occultation by the elongated centaur (95626) 2002 GZ
P. Santos-Sanz, J. L. Ortiz, B. Sicardy +56
We predicted a stellar occultation of the bright star Gaia DR1 4332852996360346368 (UCAC4 385-75921) (m= 14.0 mag) by the centaur 2002 GZ for 2017 May 20$^{\rm th}…
New insights on the binary asteroid 121 Hermione
P. Descamps, F. Marchis, J. Durech +29
We report on the results of a six-month photometric study of the main-belt binary C-type asteroid 121 Hermione, performed during its 2007 opposition. We took advantage of the rare…
The trans-Neptunian object (84922) 2003 VS2 through stellar occultations
Gustavo Benedetti-Rossi, P. Santos-Sanz, J. L. Ortiz +50
We present results from three world-wide campaigns that resulted in the detections of two single-chord and one multi-chord stellar occultations by the Plutino object (84922) 2003~V…
New orbits of irregular satellites designed for the predictions of stellar occultations up to 2020, based on thousands of new observations
A. R. Gomes-Júnior, M. Assafin, L. Beauvalet +5
Gomes-Júnior et al. (2015) published 3613 positions for the 8 largest irregular satellites of Jupiter and 1787 positions for the largest irregular satellite of Saturn, Phoebe. The…
Pluto's atmosphere from the 29 June 2015 ground-based stellar occultation at the time of the New Horizons flyby
B. Sicardy, J. Talbot, E. Meza +65
We present results from a multi-chord Pluto stellar occultation observed on 29 June 2015 from New Zealand and Australia. This occurred only two weeks before the NASA New Horizons f…
Orbit determination of Transneptunian objects and Centaurs for the prediction of stellar occultations
J. Desmars, J. I. B. Camargo, F. Braga-Ribas +10
The prediction of stellar occultations by Transneptunian objects and Centaurs is a difficult challenge that requires accuracy both in the occulted star position as for the object e…
Astrometry of the main satellites of Uranus: 18 years of observations
J. I. B. Camargo, F. P. Magalhães, R. Vieira-Martins +7
We determine accurate positions of the main satellites of Uranus: Miranda, Ariel, Umbriel, Titania, and Oberon. Positions of Uranus, as derived from those of these satellites, are…
Pluto's atmosphere from stellar occultations in 2012 and 2013
A. Dias-Oliveira, B. Sicardy, E. Lellouch +42
We analyze two multi-chord stellar occultations by Pluto observed on July 18th, 2012 and May 4th, 2013, and monitored respectively from five and six sites. They provide a total of…
Physical Characteristics of Jupiter's Trojan (1437) Diomedes from a Tri-chord Stellar Occultation in 2020 and Dimensionless 3D Model
H. Dutra, M. Assafin, B. Sicardy +15
Jupiter Trojans preserve primitive formation characteristics due to their collisionless stable orbits. Determination of their shapes and size-frequency distribution constrains the…
A large topographic feature on the surface of the trans-Neptunian object (307261) 2002 MS measured from stellar occultations
F. L. Rommel, F. Braga-Ribas, J. L. Ortiz +201
This work aims at constraining the size, shape, and geometric albedo of the dwarf planet candidate 2002 MS4 through the analysis of nine stellar occultation events. Using multichor…
Pluto's lower atmosphere and pressure evolution from ground-based stellar occultations, 1988-2016
E. Meza, B. Sicardy, M. Assafin +167
Context. Pluto's tenuous nitrogen (N2) atmosphere undergoes strong seasonal effects due to high obliquity and orbital eccentricity, and has been recently (July 2015) observed by th…
Astrometry with PRAIA
M. Assafin
PRAIA - Package for the Reduction of Astronomical Images Automatically - is a suite of astrometric and photometric tasks designed to cope with huge amounts of heterogeneous observa…
APPROX -- Mutual approximations between the Galilean moons. The 2016-2018 observational campaign
B. Morgado, R. Vieira-Martins, M. Assafin +23
The technique of mutual approximations accurately gives the central instant at the maximum apparent approximation of two moving natural satellites in the sky plane. This can be use…
Milliarcsecond astrometry for the Galilean moons using stellar occultations
B. E. Morgado, A. R. Gomes-Júnior, F. Braga-Ribas +40
A stellar occultation occurs when a Solar System object passes in front of a star for an observer. This technique allows the determination of sizes and shapes of the occulting body…
Physical properties of the trans-Neptunian object (38628) Huya from a multi-chord stellar occultation
P. Santos-Sanz, J. L. Ortiz, B. Sicardy +85
Within our international program to obtain accurate physical properties of trans-Neptunian objects (TNOs) we predicted a stellar occultation by the TNO (38628) Huya of the star Gai…
Detection and characterisation of binary asteroid candidates through stellar occultations
R. Lallemand, J. Desmars, B. Sicardy +256
Binary asteroids provide key access to fundamental parameters of Solar System remnants and planetary formations. However, the current knowledge of binary asteroids remains strongly…
Constraining the size, shape, and albedo of the large Trans-Neptunian Object (28978) Ixion with multi-chord stellar occultations
Y. Kilic, F. Braga-Ribas, C. L. Pereira +81
Trans-Neptunian objects (TNOs) are among the most primitive remnants of the early Solar System, and constraining their sizes, shapes, albedos, and surface properties is essential f…
Triplicity and Physical Characteristics of Asteroid (216) Kleopatra
Pascal Descamps, F. Marchis, J. Berthier +16
To take full advantage of the September 2008 opposition passage of the M-type asteroid (216) Kleopatra, we have used near-infrared adaptive optics (AO) imaging with the W.M. Keck I…
A study of centaur (54598) Bienor from multiple stellar occultations and rotational light curves
J. L. Rizos, E. Fernández-Valenzuela, J. L. Ortiz +40
Centaurs, distinguished by their volatile-rich compositions, play a pivotal role in understanding the formation and evolution of the early solar system, as they represent remnants…
Physical properties of Centaur (60558) 174P/Echeclus from stellar occultations
C. L. Pereira, F. Braga-Ribas, B. Sicardy +42
The Centaur (60558) Echeclus was discovered on March 03, 2000, orbiting between the orbits of Jupiter and Uranus. After exhibiting frequent outbursts, it also received a comet desi…
Pluto's Atmosphere Does Not Collapse
C. B. Olkin, L. A. Young, D. Borncamp +21
Combining stellar occultation observations probing Pluto's atmosphere from 1988 to 2013 and models of energy balance between Pluto's surface and atmosphere, we conclude that Pluto'…
Stellar occultations enable milliarcsecond astrometry for Trans-Neptunian objects and Centaurs
F. L. Rommel, F. Braga-Ribas, J. Desmars +66
Trans-Neptunian objects (TNOs) and Centaurs are remnants of our planetary system formation, and their physical properties have invaluable information for evolutionary theories. Ste…
Constraints on (2060) Chiron's size, shape, and surrounding material from the November 2018 and September 2019 stellar occultations
Felipe Braga-Ribas, C. L. Pereira, B. Sicardy +24
After the discovery of rings around the largest known Centaur object, (10199) Chariklo, we carried out observation campaigns of stellar occultations produced by the second-largest…
Centaur 29P/Schwassmann-Wachmann 1 and its near-nucleus environment from a stellar occultation
C. L. Pereira, F. Braga-Ribas, B. Sicardy +9
Comets offer valuable insights into the early Solar System's conditions and processes. Stellar occultations enables detailed study of cometary nuclei typically hidden by their coma…
The multichord stellar occultation on 2019 October 22 by the trans-Neptunian object (84922) 2003 VS
M. Vara-Lubiano, G. Benedetti-Rossi, P. Santos-Sanz +60
We predicted, observed, and analyzed the multichord stellar occultation of the Second Gaia Data Release (Gaia DR2) source 3449076721168026624 (m = 14.1 mag) by the plutino obje…
Physical properties of trans-Neptunian object (143707) 2003 UY117 derived from stellar occultation and photometric observations
M. Kretlow, J. L. Ortiz, J. Desmars +49
Trans-Neptunian objects (TNOs) are considered to be among the most primitive objects in our Solar System. Knowledge of their primary physical properties is essential for understand…
A high geometric albedo and small size of the Haumea cluster member (24835) 1995 SM55 from a stellar occultation and photometric observations
J. L. Ortiz, N. Morales, B. Sicardy +98
Trans-Neptunian objects (TNOs) are among the most ancient bodies of the solar system. Understanding their physical properties is key to constraining their origin and the evolution…
Update of membership and mean proper motion of open clusters from UCAC5 catalog
W. S. Dias, H. Monteiro, M. Assafin
We present mean proper motions and membership probabilities of individual stars for optically visible open clusters, which have been determined using data from the UCAC5 catalog. T…
Multiple Asteroid Systems: Dimensions and Thermal Properties from Spitzer Space Telescope and Ground-Based Observations
F. Marchis, J. E. Enriquez, J. P. Emery +13
Photometric lightcurves were also obtained for 14 of them during the Spitzer observations to provide the context of the observations and reliable estimates of their absolute magnit…
The 2021 mutual phenomena involving the Galilean satellites of Jupiter and the inner satellite Thebe
L. M. Catani, M. Assafin, B. E. Morgado +7
Astrometric studies and orbital modeling of planetary moons have contributed significantly to advancing our understanding of their orbital dynamics. These studies require precise p…
SPARC4: A Simultaneous Polarimeter and Rapid Camera in 4 Bands
C. V. Rodrigues, F. J. Jablonski, K. Taylor +13
We present the basic concept of a new astronomical instrument: SPARC4 - Simultaneous Polarimeter and Rapid Camera in 4 bands. SPARC4 combines in one instrument: (i) photometric and…
The structure of Chariklo's rings from stellar occultations
D. Bérard, B. Sicardy, J. I. B. Camargo +79
Two narrow and dense rings (called C1R and C2R) were discovered around the Centaur object (10199) Chariklo during a stellar occultation observed on 2013 June 3. Following this disc…
Candidate stellar occultations by large trans-neptunian objects up to 2015
M. Assafin, J. I. B. Camargo, R. Vieira Martins +4
We study large trans-neptunian objects (TNOs) using stellar occultations. We derive precise astrometric predictions for stellar occultations by Eris, Haumea, Ixion, Makemake, Orcus…
The Large Quasar Reference Frame (LQRF) - an optical representation of the ICRS
A. H. Andrei, J. Souchay, N. Zacharias +9
The large number and all-sky distribution of quasars from different surveys, along with their presence in large, deep astrometric catalogs,enables the building of an optical materi…