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Pluto's atmosphere from stellar occultations in 2012 and 2013
Dias-Oliveira, Alex; Sicardy, Bruno; Lellouch, Emmanuel et al.
2015In Bulletin of the American Astronomical Society, 47, p. 200.09
 

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Keywords :
asteroids; occultation; solar system
Abstract :
[en] We present results from two Pluto stellar occultations observed on 18 July 2012 and 04 May 2013, and monitored respectively from five and six sites in South America. Both campaigns involved large telescopes (including the 8.2-m VLT at ESO/Paranal). The high SNR ratios and multi-chord coverage provide amoung the best Pluto atmospheric profiles ever obtained from the ground.We show that a spherically symmetric, clear (no-haze) and pure N2 atmosphere with a unique temperature profile satisfactorily fits the twelve lightcurves provided by the two events. We find, however, a small but significant increase of pressure of 6% (6-sigma level) between the two dates, with values of 2.16 ± 0.2 and 2.30 ± 0.01 μbar at the reference radius 1275 km, respectively.We provide atmospheric constrains between 1190 km and 1450 km from Pluto's center, and we determine the temperature profile with accuracy of a few km in vertical scale. Our model shows a stratosphere with strong positive gradient between 1190 km (at 36 K, 11 μbar) and r =1215 km (6.0 μbar), where a temperature maximum of 110 K is reached. Above it is a mesosphere with negative thermal gradient of -0.2 K/km up to 1,390 km (0.25 μbar), at which point, the mesosphere connects itself to a more isothermal upper branch at 81 K. This profile provides (assuming no troposphere) a Pluto surface radius of 1190 ± 5 km, consistent with preliminary values obtained by New Horizons. Currently measured CO abundances are too low to explain the negative mesospheric thermal gradient. We explore the possibility of an HCN (recently detected by ALMA) cooling. This model, however, requires largely supersaturated HCN. Zonal winds and vertical compositional variations of the atmosphere are also unable to explain the observed mesospheric trend.These events are the last useful ground-based occultations recorded before the 29 June 2015 occultation observed from Australia and New Zealand, and before the NASA's New Horizons flyby of July 2015. This work can serve as a benchmark in the New Horizons context, enabling comparisons between ground-based and space results concerning Pluto's atmospheric structure and temporal evolution.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Dias-Oliveira, Alex;  Observatório Nacional
Sicardy, Bruno;  Observatoire de Paris/LESIA
Lellouch, Emmanuel;  Observatoire de Paris/LESIA
Vieira-Martins, Roberto;  Observatório Nacional
Assafin, Marcelo;  Observatório do Valongo/UFRJ
Ignácio Bueno Camargo, Júlio;  Observatório Nacional
Braga-Ribas, Felipe;  UTFPR
Gomes-Júnior, Altair;  Observatório do Valongo/UFRJ
Bendetti-Rossi, Gustavo;  Observatório Nacional
Colas, François;  Observatoire de Paris/IMCCE
Decock, Alice;  Observatoire de Paris/LESIA
Doressoundiram, Alain;  Observatoire de Paris/LESIA
Dumas, Christophe;  ESO
Emílio, Marcelo;  UEPG
Fabrega Polleri, Joaquin;  Observatório Panemño
Gil-Hutton, Ricardo;  CASLEO-CONICET
Gillon, Michaël  ;  Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa)
Girard, Julien;  ESO
Hau, George;  ESO
Ivanov, Valentin;  ESO
Jehin, Emmanuel  ;  Université de Liège - ULiège
Lecacheux, Jean;  Observatoire de Paris/IMCCE
Leiva, Rodrigo;  PUC
Lopez-Sisterna, Cecília;  Universidade Nacional de San Juan
Mancini, Luigi;  Max Planck Institute for Astronomy
Manfroid, Jean  ;  Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO)
Maury, Alain;  S.P.A.C.E
Meza, Erick;  Observatoire de Paris/LESIA
Morales, Nicolas;  Instituto de Astrofísica de Andalucía
Nagy, Leslie;  S.P.A.C.E
Opitom, Cyrielle ;  Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa)
Ortiz, José Luiz;  Instituto de Astrofísica de Andalucía
Pollock, Joe;  Appalachian State University
Roques, Françoise;  Observatoire de Paris/LESIA
Snodgrass, Colin;  The Open University
François Soulier, Jean;  Association Des 'Etoiles pour Tous
Thirouin, Audrey;  Lowell Observatory
Vanzi, Leonardo;  PUC
Widemann, Thomas;  Observatoire de Paris/LESIA
Reichart, Daniel;  Lowell Observatory
LaCluyze, Aaron;  University of North Carolina
Haislip, Joshua B.;  University of North Carolina
Ivarsen, Kevin;  University of North Carolina
Dominik, Martin;  University of St Andrews
Jørgensen, Uffe;  University of Copenhagen
Skottfelt, Jesper;  University of Copenhagen)
More authors (36 more) Less
Language :
English
Title :
Pluto's atmosphere from stellar occultations in 2012 and 2013
Publication date :
01 November 2015
Event name :
47th DPS Meeting
Event place :
Washington DC, United States
Event date :
8-13 November 2015
Audience :
International
Journal title :
Bulletin of the American Astronomical Society
ISSN :
0002-7537
eISSN :
2330-9458
Publisher :
American Astronomical Society, New York, United States - New York
Volume :
47
Pages :
200.09
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since 12 February 2016

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