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1. Lower atmosphere and pressure evolution on Pluto from ground-based stellar occultations, 1988–2016

Author

Jean Lecacheux, Michaël Gillon, Jean Manfroid, Josselin Desmars, Robert R. Howell, T. R. Marsh, G. Benedetti-Rossi, J. G. Greenhill, A. Dias-Oliveira, Ilan Manulis, G. Wortmann, K. M. Ivarsen, J.-E. Communal, S. Renner, F. Vachier, L. Tzouganatos, M. Irzyk, P. Machado, M. Harnisch, Lawrence H. Wasserman, J. Broughton, V. Lorenzi, W. H. Allen, W. Beisker, G. Murawsky, A. Magazzu, David Polishook, J. Marques Oliveira, A. R. Gomes-Junior, M. Conti, J. P. Godard, M. Lavayssière, G. Krannich, Lawrence A. Molnar, Federica B. Bianco, S. de Visscher, Leslie A. Young, Maxime Devogele, Marcelo Assafin, Alessandro Marchini, B. Kattentidt, P. Barroy, G. Dangl, A. Eberle, J. B. Haislip, K. M. Hill, Nora Morales, Andrew A. Cole, P. Enskonatus, B. Loader, Emilio Molinari, V. S. Dhillon, O. Klös, M. Ait Moulay Larbi, Bruno Sicardy, Tanguy Bertrand, Richard Querel, K. Walzel, Diane Berard, P. Lindner, J. P. Rivet, Y. Moulane, L. Di Fabrizio, Rene Duffard, D. Vérilhac, G. McKay, Raoul Behrend, Emmanuel Jehin, Fabio Salvaggio, Greg Bolt, Ricardo Gil-Hutton, J. Milner, Martin Jelínek, J. Sérot, D. Vernet, Kosmas Gazeas, F. Signoret, K. L. Bath, A. C. Gilmore, E. Lellouch, D. Herald, A. Selva, D. Lanoiselée, M. Boutet, Ph. Bendjoya, Shai Kaspi, E. Meza, John Talbot, S. P. Littlefair, Alain Maury, Roberto Vieira-Martins, Marc W. Buie, F. Jabet, S. Kerr, A. Román, Thomas Widemann, C. Opitom, R. Zanmar Sanchez, P. B. Graham, E. Frappa, Catherine B. Olkin, H.-J. Bode, H. Eichler, J. De Queiroz, K. Lindner, A. P. LaCluyze, Zouhair Benkhaldoun, D. Gault, Alain Doressoundiram, François Forget, Riccardo Papini, T. Dobosz, B. E. Morgado, J. Rovira, B. Lade, Daniel E. Reichart, O. Faragó, R. Jansen, Luigi Mancini, A. Noschese, Noah Brosch, Felipe Braga-Ribas, A. Daassou, H. Pavlov, A. Carbognani, S. Todd, F. Colas, Y. El Azhari, C. Peterson, V. Tsamis, M. Bretton, J. Hattenbach, F. Ciabattari, Rodrigo Leiva, C. Veillet, A. J. Castro Tirado, Joe Pollock, R. Naves, Pablo Santos-Sanz, D. Hampf, D. Neel, J. L. Ortiz, S. Alonso, L. Abe, P. M. Kilmartin, Julio Camargo, J. M. Ohlert, D. Gloistein, K. Tigani, F. Marchis, M. Dohrmann, Richard G. French, Ronan Cunniffe, T. Janik, Tamás Tordai, E. F. Young, S. Parker, G. Bonnoli, A. Pennell, M. Kretlow, P. Sogorb, Z. Moravec, W. Rothe, C. Perelló, K. Guhl, A. B. Giles, B. Gährken, Françoise Roques, Valentin D. Ivanov, Giuseppe Leto, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Observatório do Valongo/UFRJ [Rio de Janeiro], Universidade Federal do Rio de Janeiro (UFRJ), Centre Hospitalier Universitaire de Nîmes (CHU Nîmes), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Lille-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Ludwig Maximilians University of Munich, Southwest Research Institute [Boulder] (SwRI), Observatorio Nacional [Rio de Janeiro], Universidade Estadual Paulista Júlio de Mesquita Filho = São Paulo State University (UNESP), Observatório Nacional/MCT, Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), Instituto de Astrofísica de Andalucía (IAA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), UZEI PRAGUE CZE, Partenaires IRSTEA, Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), National Institute of Water and Atmospheric Research [Lauder] (NIWA), European Southern Observatory [Santiago] (ESO), European Southern Observatory (ESO), Institut d'Astrophysique et de Géophysique [Liège], Université de Liège, Space Sciences, Technologies and Astrophysics Research Institute (STAR), Department of Physics and Astronomy [Boone], Appalachian State University, University of North Carolina System (UNC)-University of North Carolina System (UNC), Département d'Astrophysique (ex SAP) (DAP), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Universidad Nacional de San Juan (UNSJ), University of Sheffield [Sheffield], Kuriwa Observatory, Astronomical Association of Queensland (AAQ), Euraster, Observatoire de Dax, Cardiff School of European Studies (CSES), Cardiff University, Department of Earth, Planetary and Space Sciences [Los Angeles] (EPSS), University of California [Los Angeles] (UCLA), University of California-University of California, Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Fundació Privada Observatori Esteve Duran, The Wise Observatory and The Raymond & Beverly Sackler School of Physics and Astronomy, Tel Aviv University [Tel Aviv], Wise Observatory and Department of geophysics and planetary sciences, Université Cadi Ayyad [Marrakech] (UCA), Stockport Observatory, Occultation Section [Wellington], Royal Astronomical Society of New Zealand, Laboratoire Hippolyte Fizeau (FIZEAU), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Observatoire de la Côte d'Azur (OCA), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides (CASSIOPEE), Università degli Studi di Perugia (UNIPG), Institut Pascal (IP), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-SIGMA Clermont (SIGMA Clermont)-Centre National de la Recherche Scientifique (CNRS), Polska Akademia Nauk = Polish Academy of Sciences (PAN), Astronomical Union of Sparta [Sparta], Laboratoire de Physique de la Matière Condensée - UR UPJV 2081 (LPMC), Université de Picardie Jules Verne (UPJV), PEIRENE (PEIRENE), Institut Génomique, Environnement, Immunité, Santé, Thérapeutique (GEIST), Université de Limoges (UNILIM)-Université de Limoges (UNILIM), Obervatoire des Baronnies Provençales (OBP), Observatorio Montcabre, Institut Laue-Langevin (ILL), ILL, ITA, USA, GBR, FRA, DEU, ESP, ARG, AUS, AUT, BEL, BRA, CHL, GRC, ISR, MAR, NZL, POL, PRT, CZE, CHE, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Ludwig-Maximilians University [Munich] (LMU), Université de Genève = University of Geneva (UNIGE), Universidad Nacional de San Juan [Argentine] (UNSJ), University of California (UC)-University of California (UC), Université Nice Sophia Antipolis (1965 - 2019) (UNS), Tel Aviv University (TAU), Università degli Studi di Perugia = University of Perugia (UNIPG), Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brasil), Ministerio de Economía y Competitividad (España), European Research Council, European Commission, Ministerio de Ciencia, Innovación y Universidades (España), and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Brasil)

Subjects
planets and satellites: physical evolution, 010504 meteorology & atmospheric sciences, Orbital eccentricity, Context (language use), Surface pressure, Atmospheric sciences, 7. Clean energy, 01 natural sciences, planets and satellites: terrestrial planets, Atmosphere, techniques: photometric, Altitude, Settore FIS/05 - Astronomia e Astrofisica, 0103 physical sciences, methods: observational, methods: data analysis, planets and satellites: atmospheres, observational [Methods], data analysis [Methods], 010303 astronomy & astrophysics, physical evolution [Planets and satellites], Optical depth, 0105 earth and related environmental sciences, methods: observational, methods: data analysis, planets and satellites: atmospheres, techniques: photometric, planets and satellites: physical evolution, planets and satellites: terrestrial planets, Astrophysics - Earth and Planetary Astrophysics, photometric [Techniques], Astronomy and Astrophysics, Albedo, Pluto, 13. Climate action, Space and Planetary Science, terrestrial planets [Planets and satellites], atmospheres [Planets and satellites], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Geology, Astrophysics - Earth and Planetary Astrophysics
Abstract

This article is dedicated to the memory of H.-J. Bode, J. G. Greenhill and O. Faragó for their long-standing support and participation to occultation campaigns. The work leading to these results has received funding from the European Research Council under the European Community’s H2020 2014-2020 ERC Grant Agreement n° 669416 “Lucky Star”. E.M. thanks support from Concytec-Fondecyt-PE and GA, FC-UNI for providing support during the 2012 July 18 occultation. B.S. thanks S. Para for partly supporting this research though a donation, J. P. Beaulieu for helping us accessing to the Hobart Observatory facilities and B. Warner, B. L. Gary, C. Erickson, H. Reitsema, L. Albert, P. J. Merritt, T. Hall, W. J. Romanishin, Y. J. Choi for providing data during the 2007 March 18 occultation. M.A. thanks CNPq (Grants 427700/2018-3, 310683/2017-3 and 473002/2013-2) and FAPERJ (Grant E-26/111.488/2013). J.L.O. thanks support from grant AYA2017-89637-R. P.S.S. acknowledges financial support from the European Union’s Horizon 2020 Research and Innovation Programme, under Grant Agreement no 687378, as part of the project “Small Bodies Near and Far” (SBNAF). J.L.O., R.D., P.S.S. and N.M. acknowledge financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709). F.B.R. acknowledges CNPq support process 309578/2017-5. G.B.R. thanks support from the grant CAPES-FAPERJ/PAPDRJ (E26/203.173/2016). J.I.B.C. acknowledges CNPq grant 308150/2016-3. R.V.M. thanks the grants: CNPq-304544/2017-5, 401903/2016-8, and Faperj: PAPDRJ-45/2013 and E-26/203.026/2015. B.M. thanks the CAPES/Cofecub-394/2016-05 grant and CAPES/Brazil – Finance Code 001. B.M. and A.R.G.J. were financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) – Finance Code 001. TRAPPIST-North is a project funded by the University of Liège, in collaboration with Cadi Ayyad University of Marrakech (Morocco). TRAPPIST-South is a project funded by the Belgian Fonds (National) de la Recherche Scientifique (F.R.S.-FNRS) under grant FRFC 2.5.594.09.F, with the participation of the Swiss National Science Foundation (FNS/SNSF). VSD, SPL, TRM and ULTRACAM are all supported by the STFC. K.G. acknowledges help from the team of Archenhold-Observatory, Berlin, and A.R. thanks G. Román (Granada) for help during the observation of the 2016 July 19 occultation. A.J.C.T. acknowledges support from the Spanish Ministry Project AYA2015-71718-R (including EU funds). We thank Caisey Harlingten for the repeated use of his 50 cm telescopes in San Pedro de Atacama, Chile. We thank the Italian Telescopio Nazionale Galileo (TNG), operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. L.M. acknowledges support from the Italian Minister of Instruction, University and Research (MIUR) through FFABR 2017 fund and support from the University of Rome Tor Vergata through “Mission: Sustainability 2016” fund. The Astronomical Observatory of the Autonomous Region of the Aosta Valley (OAVdA) is managed by the Fondazione Clément Fillietroz-ONLUS, which is supported by the Regional Governmentof the Aosta Valley, the Town Municipality of Nus and the “Unité des Communes valdôtaines Mont-Émilius”. The research was partially funded by a 2016 “Research and Education”s grant from Fondazione CRT. We thank D.P. Hinson for his constructive and detailed comments that helped to improve this article., Context. The tenuous nitrogen (N2) atmosphere on Pluto undergoes strong seasonal effects due to high obliquity and orbital eccentricity, and has recently (July 2015) been observed by the New Horizons spacecraft. Aims. The main goals of this study are (i) to construct a well calibrated record of the seasonal evolution of surface pressure on Pluto and (ii) to constrain the structure of the lower atmosphere using a central flash observed in 2015. Methods. Eleven stellar occultations by Pluto observed between 2002 and 2016 are used to retrieve atmospheric profiles (density, pressure, temperature) between altitude levels of ~5 and ~380 km (i.e. pressures from ~ 10 μbar to 10 nbar). Results. (i) Pressure has suffered a monotonic increase from 1988 to 2016, that is compared to a seasonal volatile transport model, from which tight constraints on a combination of albedo and emissivity of N2 ice are derived. (ii) A central flash observed on 2015 June 29 is consistent with New Horizons REX profiles, provided that (a) large diurnal temperature variations (not expected by current models) occur over Sputnik Planitia; and/or (b) hazes with tangential optical depth of ~0.3 are present at 4–7 km altitude levels; and/or (c) the nominal REX density values are overestimated by an implausibly large factor of ~20%; and/or (d) higher terrains block part of the flash in the Charon facing hemisphere., European Research Council under the European Community’s H2020 2014-2020 ERC Grant Agreement n° 669416 “Lucky Star”, Grants 427700/2018-3, 310683/2017-3 and 473002/2013-2) and FAPERJ (Grant E-26/111.488/2013), Grant AYA2017-89637-R. P.S.S. acknowledges financial support from the European Union’s Horizon 2020 Research and Innovation Programme, under Grant Agreement no 687378, as part of the project “Small Bodies Near and Far” (SBNAF), Financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709), Support process 309578/2017-5. G.B.R. thanks support from the grant CAPES-FAPERJ/PAPDRJ (E26/203.173/2016). J.I.B.C. acknowledges CNPq grant 308150/2016-3. R.V.M. thanks the grants: CNPq-304544/2017-5, 401903/2016-8, and Faperj: PAPDRJ-45/2013 and E-26/203.026/2015. B.M. thanks the CAPES/Cofecub-394/2016-05 grant and CAPES/Brazil – Finance Code 001., Grant FRFC 2.5.594.09.F, with the participation of the Swiss National Science Foundation (FNS/SNSF), Support from the Spanish Ministry Project AYA2015-71718-R (including EU funds), Support from the Italian Minister of Instruction, University and Research (MIUR) through FFABR 2017 fund and support from the University of Rome Tor Vergata through “Mission: Sustainability 2016” fund

Published
2019

2. Size and Shape of Chariklo from Multi-epoch Stellar Occultations

Author

R. Vieira-Martins, Amanda A. Sickafoose, H. Breytenbach, K.-L. Bath, Rene Duffard, Bruno Sicardy, Pierre Kervella, C. De Witt, B. Lade, S. Kerr, D. Bérard, A. Cool, L. Maquet, P. Schoenau, Jose L. Ortiz, G. Benedetti-Rossi, Felipe Braga-Ribas, François Colas, H.-J. Bode, Marcelo Assafin, D. Herald, Nicolás Morales, B. E. Morgado, Josselin Desmars, Julio Camargo, E. Meza, A. R. Gomes-Júnior, Emmanuel Lellouch, J.-L. Dauvergne, Rodrigo Leiva, Colin Snodgrass, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de Lille-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Sonnensystemforschung (MPS), Max-Planck-Gesellschaft, Instituto de Astrofísica de Andalucía (IAA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Observatorio Nacional [Rio de Janeiro], Observatório Nacional/MCT, Observatório do Valongo/UFRJ [Rio de Janeiro], Universidade Federal do Rio de Janeiro (UFRJ), L2EP - Équipe Réseaux, Laboratoire d’Électrotechnique et d’Électronique de Puissance - ULR 2697 (L2EP), Centrale Lille-Haute Etude d'Ingénieurs-Université de Lille-Arts et Métiers Sciences et Technologies, HESAM Université (HESAM)-HESAM Université (HESAM)-Centrale Lille-Haute Etude d'Ingénieurs-Université de Lille-Arts et Métiers Sciences et Technologies, HESAM Université (HESAM)-HESAM Université (HESAM), Springbok, Stockport Observatory, Astronomical Association of Queensland (AAQ), Canberra Astronomical Society, Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), PSL Research University (PSL)-PSL Research University (PSL)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Consejo Superior de Investigaciones Científicas [Spain] (CSIC), Universidade Federal do Rio de Janeiro [Rio de Janeiro] (UFRJ), Laboratoire d’Électrotechnique et d’Électronique de Puissance - EA 2697 (L2EP), Ecole Centrale de Lille-École Nationale Supérieure d'Arts et Métiers (ENSAM), Arts et Métiers Sciences et Technologies, HESAM Université (HESAM)-HESAM Université (HESAM)-Arts et Métiers Sciences et Technologies, HESAM Université (HESAM)-HESAM Université (HESAM)-Haute Etude d'Ingénieurs-Université de Lille-Ecole Centrale de Lille-École Nationale Supérieure d'Arts et Métiers (ENSAM), and HESAM Université (HESAM)-HESAM Université (HESAM)-Haute Etude d'Ingénieurs-Université de Lille

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Physics, Rotation period, [PHYS]Physics [physics], 010504 meteorology & atmospheric sciences, FOS: Physical sciences, Astronomy and Astrophysics, Radius, Astrophysics, Light curve, 01 natural sciences, Ellipsoid, Photometry (optics), Spherical model, Mean motion, 13. Climate action, Space and Planetary Science, Geometric albedo, 0103 physical sciences, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Astrophysics - Earth and Planetary Astrophysics, 0105 earth and related environmental sciences
Abstract

We use data from five stellar occultations observed between 2013 and 2016 to constrain Chariklo's size and shape, and the ring reflectivity. We consider four possible models for Chariklo (sphere, Maclaurin spheroid, tri-axial ellipsoid and Jacobi ellipsoid) and we use a Bayesian approach to estimate the corresponding parameters. The spherical model has a radius $R=129\pm3$ km. The Maclaurin model has equatorial and polar radii $a=b=143^{+3}_{-6}$ km and $c=96^{+14}_{-4}$ km, respectively, with density $970^{+300}_{-180}$ kg m$^{-3}$. The ellipsoidal model has semiaxes $a=148^{+6}_{-4}$ km, $b=132^{+6}_{-5}$ km and $c=102^{+10}_{-8}$ km. Finally, the Jacobi model has semiaxes $a$=157$\pm$4 km, $b$=139$\pm$ 4 km and $c$=86$\pm$1 km, and density $796^{+2}_{-4}$ kg m$^{-3}$ . Depending on the model, we obtain topographic features of 6-11 km, typical of Saturn icy satellites with similar size and density. We constrain Chariklo's geometric albedo between 3.1\% (sphere) and 4.9\% (ellipsoid), while the ring $I/F$ reflectivity is less constrained between 0.6\% (Jacobi) and 8.9\% (sphere). The ellipsoid model explains both the optical light curve and the long-term photometry variation of the system, giving a plausible value for the geometric albedo of the ring particles of $10-15\%$. The derived Chariklo's mass of 6-8$\times10^{18}$ kg places the rings close to the 3:1 resonance between the ring mean motion and Chariklo's rotation period., Comment: Accepted for publication in AJ

Published
2017

3. Pluto's Atmosphere from the 2015 June 29 Ground-Based Stellar Occultation at the Time of the New Horizons Flyby

Author

Marcelo Assafin, J. Bradshaw, J. Milner, Jean Lecacheux, B. Loader, D. Giles, G. Benedetti-Rossi, P. A. Yock, S. Todd, P. B. Graham, P. Nosworthy, Ronan Cunniffe, D. Jenke, Dan M. Watson, M. Forbes, Felipe Braga-Ribas, D. Dunham, G. L. White, R. Horvat, P. F. Skilton, Jack D. Drummond, P. Purcell, A. Dias-Oliveira, M. Harnisch, J. L. Ortiz, Pierre Kervella, K. M. Hill, A. Pennell, R. Glassey, R. Groom, J. Broughton, J. Newman, W. Beisker, W. H. Allen, Hadrien A. R. Devillepoix, Rene Duffard, J. P. Beaulieu, M. Streamer, E. Meza, S. Kerr, R. Jansen, Bruno Sicardy, Andrew A. Cole, Diane Berard, L. Davis, A. J. Castro-Tirado, G. McKay, R. Idaczyk, D. Hooper, M. A. Barry, Martin Jelínek, A. B. Giles, Roberto Vieira-Martins, Julio Camargo, L. Field, G. Hudson, S. Parker, D. Gault, Richard Querel, H. Watanabe, M. Unwin, Josselin Desmars, A. Ramos-Gomes-Jr., B. Lade, H. Pavlov, E. Lellouch, D. Herald, John Talbot, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Occultation Section [Wellington], Royal Astronomical Society of New Zealand, Observatorio Nacional [Rio de Janeiro], Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Centre National de la Recherche Scientifique (CNRS)-Université de Lille-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Shanghai Astronomical Observatory [Shanghai] (SHAO), Chinese Academy of Sciences [Beijing] (CAS), Heriot-Watt University [Edinburgh] (HWU), Observatório do Valongo/UFRJ [Rio de Janeiro], Universidade Federal do Rio de Janeiro (UFRJ), International Occultation Timing Association European Section (IOTA ES), International Occultation Timing Association European Section, Instituto de Astrofísica de Andalucía (IAA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Instituto de Astrofsica de Andalucia, National Institute of Water and Atmospheric Research [Wellington] (NIWA), Institut d'Astrophysique de Paris (IAP), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Groningen Bioinformatics Centre, GBB, University of Groningen [Groningen], Ageing Group, Centre for Public Health, Queen's University [Belfast] (QUB), Health Center Research Institute, McGill University = Université McGill [Montréal, Canada], Reedy Creek, Center for Science Communication, University of Otago [Dunedin, Nouvelle-Zélande], Laboratoire d'Ingénierie des Matériaux de Bretagne (LIMATB), Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Université de Brest (UBO), Astronomical Society of Western Australia (ASWA), Stockport Observatory, Niels Bohr Institute [Copenhagen] (NBI), Faculty of Science [Copenhagen], University of Copenhagen = Københavns Universitet (KU)-University of Copenhagen = Københavns Universitet (KU), Observatoire de Paris - Site de Meudon (OBSPM), Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Kuriwa Observatory, Canberra Astronomical Society, Department of Electrical and Computer Engineering [Alberta], University of Alberta, Observatório Nacional/MCT, Universidade Federal do Rio de Janeiro [Rio de Janeiro] (UFRJ), International Occultation Timing Association (IOTA), Consejo Superior de Investigaciones Científicas [Spain] (CSIC), National Institute of Water and Atmospheric Research [Lauder] (NIWA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Royal Observatory (UKATC), Stanford University [Stanford], Department of Physics and Atmospheric Science [Halifax], Dalhousie University [Halifax], STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), University of Copenhagen = Københavns Universitet (UCPH)-University of Copenhagen = Københavns Universitet (UCPH), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Stanford University, Institut de Mécanique Céleste et de Calcul des Ephémérides ( IMCCE ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université de Lille-Centre National de la Recherche Scientifique ( CNRS ), Shanghai Astronomical Observatory [Shanghai] ( SHAO ), Chinese Academy of Sciences [Beijing] ( CAS ), Heriot-Watt University [Edinburgh] ( HWU ), Laboratoire d'études spatiales et d'instrumentation en astrophysique ( LESIA ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), Universidade Federal do Rio de Janeiro [Rio de Janeiro] ( UFRJ ), International Occultation Timing Association European Section ( IOTA ES ), Instituto de Astrofísica de Andalucía ( IAA ), Consejo Superior de Investigaciones Científicas [Spain] ( CSIC ), National Institute of Water and Atmospheric Research (NIWA), Lauder, New Zealand, Institut d'Astrophysique de Paris ( IAP ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), The Queen's University of Belfast, McGill University, University of Otago, Laboratoire d'Ingénierie des Matériaux de Bretagne ( LIMATB ), Université de Bretagne Sud ( UBS ) -Université de Brest ( UBO ) -Institut Brestois du Numérique et des Mathématiques ( IBNM ), Université de Brest ( UBO ) -Université de Brest ( UBO ), Astronomical Society of Western Australia, and Niels Bohr Institute ( NBI )

Subjects
[PHYS]Physics [physics], New horizons, 010504 meteorology & atmospheric sciences, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astronomy, Astronomy and Astrophysics, Surface pressure, Block (meteorology), 01 natural sciences, Atmosphere, Pluto, Temperature gradient, Flash (photography), Amplitude, 13. Climate action, Space and Planetary Science, 0103 physical sciences, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Geology, [ SDU.ASTR ] Sciences of the Universe [physics]/Astrophysics [astro-ph], ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract

International audience; We present results from a multi-chord Pluto stellar occultation observed on 2015 June 29 from New Zealand and Australia. This occurred only two weeks before the NASA New Horizons flyby of the Pluto system and serves as a useful comparison between ground-based and space results. We find that Pluto's atmosphere is still expanding, with a significant pressure increase of 5 ± 2% since 2013 and a factor of almost three since 1988. This trend rules out, as of today, an atmospheric collapse associated with Pluto's recession from the Sun. A central flash, a rare occurrence, was observed from several sites in New Zealand. The flash shape and amplitude are compatible with a spherical and transparent atmospheric layer of roughly 3 km in thickness whose base lies at about 4 km above Pluto's surface, and where an average thermal gradient of about 5 K km−1 prevails. We discuss the possibility that small departures between the observed and modeled flash are caused by local topographic features (mountains) along Pluto's limb that block the stellar light. Finally, using two possible temperature profiles, and extrapolating our pressure profile from our deepest accessible level down to the surface, we obtain a possible range of 11.9–13.7 μbar for the surface pressure.

Published
2016

4. CONSTRAINTS ON CHARON'S ORBITAL ELEMENTS FROM THE DOUBLE STELLAR OCCULTATION OF 2008 JUNE 22

Author

T. Dobosz, J. G. Greenhill, Marcelo Assafin, Bruno Sicardy, D. Buckley, W. Beisker, Greg Bolt, F. Benard, V. Batista, J.-P. Teng-Chuen-Yu, François Colas, Alain Doressoundiram, C. Gruhn, J. Broughton, J. Lecacheux, S. Mathers, Julio Camargo, Roberto Vieira-Martins, D. Gault, A. Peyrot, A. H. Andrei, J. Biggs, C. De Witt, B. Lade, S. Dieters, Dave Herald, Felipe Braga-Ribas, D. N. da Silva Neto, R. Groom, Y. Boissel, E. Frappa, Thomas Widemann, S. Kerr, F. Roques, Raoul Behrend, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), Craigie, Reedy Creek, Bankstown, International Occulting and Timing Association (IOTA), International Occulting and Timing Association, Astronomical Association of Queensland (AAQ), Association astronomique de la Réunion (AAR), Association astronomique de la Réunion, Euraster, International Occultation Timing Association European Section (IOTA ES), International Occultation Timing Association European Section, South African Astronomical Observatory (SAAO), Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Centre National de la Recherche Scientifique (CNRS)-Université de Lille-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Springbok, International Amateur Sternwarte (IAS), International Amateur Sternwarte, Institut d'Astrophysique de Paris (IAP), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Perth Observatory, School of Mathematics and Physics, University of Tasmania [Hobart, Australia] (UTAS), Astronomical Society of Western Australia (ASWA), Canberra Astronomical Society, Stockport Observatory, Southern Cross Observatory, Observatório do Valongo/UFRJ [Rio de Janeiro], Universidade Federal do Rio de Janeiro (UFRJ), Observatório Nacional/MCT, Universidade Estadual da Zona Oeste (UEZO), Universidade Estadual da Zona Oeste, Geneva Observatory, University of Geneva [Switzerland], Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Université de Genève = University of Geneva (UNIGE)

Subjects
Physics, Orbital elements, Orbital plane, 010504 meteorology & atmospheric sciences, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Orbital node, Equator, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astronomy, Astronomy and Astrophysics, Astrophysics, Ephemeris, 01 natural sciences, Pluto, True longitude, Kuiper belt objects : individual : Pluto Charon, planets and satellites : fundamental parameters, Space and Planetary Science, occultations, 0103 physical sciences, astrometry, Longitude, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract

The original publication is available at http://iopscience.iop.org/1538-3881/; International audience; 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 ± 0fdg071 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 ± 0fdg071 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 ± 0fdg071 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 × 10-3in 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.

Published
2011

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