Titania's radius and an upper limit on its atmosphere from the September 8, 2001 stellar occultation

Widemann, Thomas; Sicardy, B.; Dusser, R.; Martínez, C. Moreno; Beisker, W.; Bredner, E.; Dunham, David; Maley, P. D.; Lellouch, E.; Arlot, Jean-Eudes; Berthier, J.; Colas, F.; Hubbard, W. B.; Hill, R. E.; Lecacheux, J.; Lecampion, J.-F.; Pau, S.; Rapaport, M.; Roques, F.; Thuillot, W.; Hills, C. R.; Elliott, Andrew; Miles, Richard B.; Platt, Tristán; Cremaschini, Claudio; Dubreuil, Pascal; Cavadore, Cyril; Demeautis, C.; Henriquet, P.; Labrevoir, O.; Rau, Gioia; Coliac, J.-F.; Piraux, Joël; Marlot, C.; Gorry, F.; Sire, C.; Bayle, B.; Simian, E.; Blommers, A.M.; Fulgence, J.; Leyrat, C.; Sauzeaud, C.; Stephanus, B.; Rafaelli, T.; Buil, C.; Delmas, Robert J.; Desnoux, V.; Jasinski, C.; Klotz, A.; Marchais, D.; Rieugnié, M.; Bouderand, G.; Cazard, J.-P.; Lambin, C.; Pujat, P.O.; Schwartz, F.; Burlot, P.; Langlais, P.; Rivaud, S.; Brochard, E.; Dupouy, P.; Lavayssière, M.; Chaptal, O.; Daiffallah, K.; Clarasso-Llauger, C.; Doménech, J. Aloy; Gabaldá-Sánchez, M.; Otazu, Xavier; Fernández, D.; Masana, E.; Ardanuy, A.; Casas, R.; Ros, Javier; Casarramona, F.; Schnabel, C.; Roca, Antoni; Labordena, C.; Canales-Moreno, O.; Ferrer, V.; Rivas, L.; Ortiz, J. L.; Fernández-Arozena, J.; Martín-Rodríguez, L.L.; Cidadão, A.; Coelho, P.; Figuereido, P.; Gonçalves, R.; Marciano, C.; Nunes, Rafael C.; Ré, P.; Saraiva, Carlos; Tonel, F.; Clérigo, J.; Oliveira, Cristina; Reis, C.; Ewen-Smith, B.M.; Ward, Sammie; Ford, Dominic; Gonçalves, J.; Porto, J.; Sobrinho, J. L. G.; Gois, F. Teodoro de; Joaquim, M.; Mendes, J. Afonso da Silva; Ballegoij, Erwin van; Jones, Robert; Callender, H.; Sutherland, William J.; Bumgarner, S.; Imbert, Michel; Mitchell, B. R.; Lockhart, J.; Barrow, W.; Cornwall, D.; Arnal, A.; Eleizalde, G.; Valencia, A.; Ladino, V.; Lizardo, T.; Guillén, C. Cardona; Sánchez, Gu.; Peña, A.; Radaelli, S.; Santiago, J.; Vieira, K.; Mendt, H.; Rosenzweig, P.; Naranjo, O.; Contreras, O.; Díaz, Franklin Chang; Guzman, Edgar; Moreno, F.; Porras, L. Omar; Recalde, E.; Mascaró, M.; Birnbaum, C.; Cósias, R.; Lopez, Eric; Pallo, Edgar; Percz, R.; Pulupa, D.; Simbaña, X.; Yajamín, A.; Rodas, P.; Denzau, H.; Kretlow, M.; Sada, Pedro V.; Hernández, R. Díaz; Hernandez, Audra K.; Wilson, B. G.; Castro, E. de; Winkel, J.M.

doi:10.1016/j.icarus.2008.09.011

Cited by 29 publications

(23 citation statements)

References 31 publications

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“…Stellar occultations can also be included among those techniques since they are also a source of accurate positions (see Person et al 2006;Sicardy et al 2006;Widemann et al 2009;Benedetti-Rossi et al 2014). In the case of Pluto, for instance, one could take advantage of the fact that its photocenter displacement due to the presence of Charon is not of concern for the astrometry from stellar occultations.…”

Section: Introductionmentioning

confidence: 99%

Astrometry of the main satellites of Uranus: 18 years of observations

Camargo¹,

Magalhaes²,

Vieira-Martins³

et al. 2015

A&A

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Context. We contribute to developing dynamical models of the motions of Uranus' main satellites. Aims. 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 also determined. The observational period spans from 1992 to 2011. All runs were made at the Pico dos Dias Observatory, Brazil. Methods. We used the software called Platform for Reduction of Astronomical Images Automatically (PRAIA) to perform a digital coronography to minimise the influence of the scattered light of Uranus on the astrometric measurements and to determine accurate positions of the main satellites. The positions of Uranus were then indirectly determined by computing the mean differences between the observed and ephemeris positions of these satellites. A series of numerical filters was applied to filter out spurious data. These filters are mostly based on (a) the comparison between the positions of Oberon with those of the other satellites and on (b) the offsets as given by the differences between the observed and ephemeris positions of all satellites. Results. We have, for the overall offsets of the five satellites, −29 mas (±63 mas) in right ascension and −27 mas (±46 mas) in declination. For the overall difference between the offsets of Oberon and those of the other satellites, we have +3 mas (±30 mas) in right ascension and −2 mas (±28 mas) in declination. Ephemeris positions for the satellites were determined from DE432+ura111. Comparisons using other modern ephemerides for the solar system -INPOP13c -and for the motion of the satellites -NOE-7-2013 -were also made. They confirm that the largest contribution to the offsets we find comes from the motion of the barycenter of the Uranus system around the barycenter of the solar system, as given by the planetary ephemerides. For the period from 1992 to 2011, our final catalogues contain 584 observed positions of Miranda, 1710 of Ariel, 1987 of Umbriel, 2588 of Titania, 2928 of Oberon, and 3516 of Uranus.

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Section: Introductionmentioning

confidence: 99%

Astrometry of the main satellites of Uranus: 18 years of observations

Camargo¹,

Magalhaes²,

Vieira-Martins³

et al. 2015

A&A

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“…We have determined the disappearance (ingress) and reappearance (egress) times of the star behind Charon at Les Makes station, using a model which includes Fresnel's diffraction by a sharp edge, convolution by the instrumental bandwidth and by the stellar profile projected at Charon, and a final convolution accounting for the finite integration time for each data point, see Widemann et al (2009) for more details on the method. For practical purposes, considering the integration time (0.32 s) and shadow velocity (about 24 km s −1 ), the final synthetic occultation light curve shown in Figure 7 is largely dominated by the finite integration time, and little affected by diffraction, finite stellar size, and limb-darkening effects.…”

Section: Charon's Offsetmentioning

confidence: 99%

“…Charon's radius ranges from 604 ± 1.4 to 606 ± 1.5 km depending on authors. However, local topographic features at the level of 2-3 km may affect the local limb radius, see, e.g., the multi-chord occultation by Uranus' main satellite Titania of 2001 September 8 (Widemann et al 2009), for which a radius of 788.4 km-comparable to Charon's-was derived.…”

Section: Charon's Offsetmentioning

confidence: 99%

Constraints on Charon's Orbital Elements From the Double Stellar Occultation of 2008 June 22

Sicardy¹,

Bolt²,

Broughton³

et al. 2011

The Astronomical Journal

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Pluto and its main satellite, Charon, occulted the same star on 2008 June 22. This event was observed from Australia and La Réunion Island, providing the east and north Charon Plutocentric offset in the sky plane (J2000): X = + 12,070.5 ± 4 km (+ 546.2 ± 0.2 mas), Y = + 4,576.3 ± 24 km (+ 207.1 ± 1.1 mas) at 19:20:33.82 UT on Earth, corresponding to JD 2454640.129964 at Pluto. This yields Charon's true longitude L = 153.483 ± 0.• 071 in the satellite orbital plane (counted from the ascending node on J2000 mean equator) and orbital radius r = 19,564 ± 14 km at that time. We compare this position to that predicted by (1) the orbital solution of Tholen & Buie (the "TB97" solution), (2) the PLU017 Charon ephemeris, and (3) the solution of Tholen et al. (the "T08" solution). We conclude that (1) our result rules out solution TB97, (2) our position agrees with PLU017, with differences of ΔL = + 0.073 ± 0.• 071 in longitude, and Δr = + 0.6 ± 14 km in radius, and (3) while the difference with the T08 ephemeris amounts to only ΔL = 0.033 ± 0.• 071 in longitude, it exhibits a significant radial discrepancy of Δr = 61.3 ± 14 km. We discuss this difference in terms of a possible image scale relative error of 3.35 × 10 −3 in the 2002-2003 Hubble Space Telescope images upon which the T08 solution is mostly based. Rescaling the T08 Charon semi-major axis, a = 19, 570.45 km, to the TB97 value, a = 19636 km, all other orbital elements remaining the same ("T08/TB97" solution), we reconcile our position with the re-scaled solution by better than 12 km (or 0.55 mas) for Charon's position in its orbital plane, thus making T08/TB97 our preferred solution.

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“…rock/ice ratio). Another outstanding advantage of stellar occultations is the possibility of detecting very tenuous atmospheres around some of these bodies, down to surface pressure of a few nanobars, as reported for instance by Widemann et al (2009), Sicardy et al (2011), and Braga-Ribas et al (2013. This is four orders of magnitudes lower than Pluto's surface pressure (about 10 μbar).…”

Section: Introductionmentioning

confidence: 97%

Candidate stellar occultations by Centaurs and trans-Neptunian objects up to 2014

Camargo

Vieira-Martins

Assafin

et al. 2013

A&A

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Context. We study trans-Neptunian objects (TNOs) from stellar occultations. Aims. We predict stellar occultations from 2012.5 to the end of 2014 by 5 Centaurs and 34 TNOs. Methods. These predictions were achieved in two ways: first, we built catalogues with precise astrometric positions of the stellar content around the paths on the sky of these targets, as seen by a ground-based observer; second, the observed positions of the targets were determined with the help of these same catalogues so that we could improve their ephemerides and the reliability of the predictions. The reference system is the International Celestial Reference System (ICRS) as realised by the Fourth US Naval Observatory CCD Astrograph Catalog (UCAC4). All the sky paths as well as the selected targets were observed from Oct. 2011 to May 2013 with the ESO/MPG 2.2 m telescope equipped with the Wide Field Imager (WFI). All astrometric results were obtained with the platform for reduction of astronomical images automatically (PRAIA) after correcting the images for overscan, bias, and flatfield. Results. The catalogues with the stellar content around the sky path of each selected target are complete down to magnitude R = 19 and have an average positional accuracy of about 50 milliarcseconds. This same average accuracy also holds for the observed positions of the targets. In the catalogues from the sky paths, stellar proper motions for non-UCAC4 objects were derived from the combination of the current epoch WFI observations with either the 2MASS or the USNO-B1 catalogues. The offsets between the observed and (JPL) ephemeris positions of the targets frequently reach absolute values of some hundreds of milliarcseconds. Conclusions. We present here stellar occultation predictions for the selected 5 Centaurs and 34 TNOs from 2012.5 to the end of 2014. This work is also an extension of two previous prediction works by us, the first one for Pluto, Charon, Nix, and Hydra, and the second for ten other large TNOs. The use of catalogues from the observations of the sky paths in the astrometry of the TNOs and Centaurs enhanced the coherence between their positions and those of the respective occulted candidate stars. New observations of these TNOs and Centaurs are continuously used to redetermine their ephemerides.

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Titania's radius and an upper limit on its atmosphere from the September 8, 2001 stellar occultation

Abstract: International audienc

Cited by 29 publications

References 31 publications

Astrometry of the main satellites of Uranus: 18 years of observations

Astrometry of the main satellites of Uranus: 18 years of observations

Constraints on Charon's Orbital Elements From the Double Stellar Occultation of 2008 June 22

Candidate stellar occultations by Centaurs and trans-Neptunian objects up to 2014

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