Constraints on the structure and seasonal variations of Triton's atmosphere from the 5 October 2017 stellar occultation and previous observations

J. Marques Oliveira (1) , B. Sicardy (1) , A. R. Gomes-Júnior (2) , J. L. Ortiz (3) , D. F. Strobel (4) , T. Bertrand (1) , F. Forget (5) , E. Lellouch (1) , J. Desmars (6, 7) , D. Bérard (1) , A. Doressoundiram (1) , J. Lecacheux (1) , R. Leiva (8) , E. Meza (9, 10) , F. Roques (1) , D. Souami (1) , T. Widemann (1) , P. Santos-Sanz (3) , N. Morales (3) , R. Duffard (3) , E. Fernández-Valenzuela (3, 11) , A. J. Castro-Tirado (3) , F. Braga-Ribas (12, 13, 1) , B. E. Morgado (13, 1) , M. Assafin (14) , J. I. B. Camargo (13) , R. Vieira-Martins (13) , G. Benedetti-Rossi (1, 7) , S. Santos-Filho (14) , M. V. Banda-Huarca (13) , F. Quispe-Huaynasi (13) , C. L. Pereira (13) , F. L. Rommel (13) , G. Margoti (12) , A. Dias-Oliveira (15) , F. Colas (7) , J. Berthier (7) , S. Renner (7, 16) , R. Hueso (17) , S. Pérez-Hoyos (17) , A. Sánchez-Lavega (17) , J. F. Rojas (17) , W. Beisker (18, 19) , M. Kretlow (18, 19) , D. Herald , D. Gault , K. -L. Bath , H. -J. Bode , E. Bredner , K. Guhl , T. V. Haymes , E. Hummel , B. Kattentidt , O. Klös , A. Pratt , B. Thome , C. Avdellidou , K. Gazeas , E. Karampotsiou , L. Tzouganatos , E. Kardasis , A. A. Christou , E. M. Xilouris , I. Alikakos , A. Gourzelas , A. Liakos , V. Charmandaris , M. Jelínek , J. Štrobl , A. Eberle , K. Rapp , B. Gährken , B. Klemt , S. Kowollik , R. Bitzer , M. Miller , G. Herzogenrath , D. Frangenberg , L. Brandis , I. Pütz , V. Perdelwitz , G. M. Piehler , P. Riepe , K. von Poschinger , P. Baruffetti , D. Cenadelli , J. -M. Christille , F. Ciabattari , R. Di Luca , D. Alboresi , G. Leto , R. Zanmar Sanchez , P. Bruno , G. Occhipinti , L. Morrone , L. Cupolino , A. Noschese , A. Vecchione , C. Scalia , R. Lo Savio , G. Giardina , S. Kamoun , R. Barbosa , R. Behrend , M. Spano , E. Bouchet , M. Cottier , L. Falco , S. Gallego , L. Tortorelli , S. Sposetti , J. Sussenbach , F. van den Abbeel , P. André , M. Llibre , F. Pailler , J. Ardissone , M. Boutet , J. Sanchez , M. Bretton , A. Cailleau , V. Pic , L. Granier , R. Chauvet , M. Conjat (8) , J. L. Dauvergne , O. Dechambre , P. Delay , M. Delcroix (20) , L. Rousselot (20) , J. Ferreira (8) , P. Machado , P. Tanga (8) , J. -P. Rivet (8) , E. Frappa , M. Irzyk , F. Jabet , M. Kaschinski , Y. Rieugnie , A. N. Klotz (21) , O. Labrevoir , D. Lavandier , D. Walliang , A. Leroy , Sylvain Bouley (22) , S. Lisciandra , J. -F. Coliac , F. Metz , D. Erpelding , P. Nougayrède , T. Midavaine , M. Miniou , S. Moindrot , P. Morel , B. Reginato , E. Reginato (23, 24) , J. Rudelle , B. Tregon (25) , R. Tanguy , J. David , W. Thuillot (7) , D. Hestroffer (7) , G. Vaudescal , D. Baba Aissa , Z. Grigahcene , D. Briggs , S. Broadbent , P. Denyer , N. J. Haigh , N. Quinn , G. Thurston , S. J. Fossey , C. Arena , M. Jennings , J. Talbot , S. Alonso , A. Román Reche , V. Casanova , E. Briggs , R. Iglesias-Marzoa , J. Abril Ibáñez , M. C. Díaz Martín , H. González , J. L. Maestre García , J. Marchant , I. Ordonez-Etxeberria , P. Martorell , J. Salamero , F. Organero , L. Ana , F. Fonseca , V. Peris , O. Brevia , A. Selva , C. Perello , V. Cabedo , R. Gonçalves , M. Ferreira , F. Marques Dias , A. Daassou , K. Barkaoui , Z. Benkhaldoun , M. Guennoun , J. Chouqar , E. Jehin , C. Rinner , J. Lloyd , M. El Moutamid , C. Lamarche , J. T. Pollock , D. B. Caton , V. Kouprianov , B. W. Timerson , G. Blanchard , B. Payet , A. Peyrot , J. -P. Teng-Chuen-Yu , J. Françoise , B. Mondon , T. Payet , C. Boissel , M. Castets , W. B. Hubbard , R. Hill , H. J. Reitsema , O. Mousis (26) , L. Ball , G. Neilsen , S. Hutcheon , K. Lay , P. Anderson , M. Moy , M. Jonsen , I. Pink , B. Downs , R. Walters

1 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics
2 UNESP - Universidade Estadual Paulista Júlio de Mesquita Filho = São Paulo State University
3 IAA - Instituto de Astrofísica de Andalucía
4 JHU - Johns Hopkins University
5 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)
6 IPSA - Institut Polytechnique des Sciences Avancées
7 IMCCE - Institut de Mécanique Céleste et de Calcul des Ephémérides
8 OCA - Observatoire de la Côte d'Azur
9 CONIDA - Comisión Nacional de Investigación y Desarrollo Aeroespacial
10 Observatorio Astronómico de Moquegua
11 FSI - Florida Space Institute [Orlando]
12 UTFPR - Universidade Tecnológica Federal do Paraná [Curitiba, Brasil] = Federal Technological University of Paraná [Curitiba, Brazil] = Université technologique fédérale du Paraná [Curitiba, Brésil]
13 ON - Observatório Nacional [Rio de Janeiro]
14 UFRJ - Universidade Federal do Rio de Janeiro [Brasil] = Federal University of Rio de Janeiro [Brazil] = Université fédérale de Rio de Janeiro [Brésil]
15 Polo Educacional Sesc [Rio de Janeiro]
16 Université de Lille
17 UPV/EHU - Universidad del Pais Vasco / Euskal Herriko Unibertsitatea [Espagne]
18 IOTA - International Occultation Timing Association
19 IAS - Internationale Amateursternwarte [Mittenwalde]
20 SAF - Société Astronomique de France
21 IRAP - Institut de recherche en astrophysique et planétologie
22 GEOPS - Géosciences Paris Saclay
23 UP11 - Université Paris-Sud - Paris 11
24 MICROCOSME - Analyse, ingénierie et contrôle des micro-organismes
25 LOMA - Laboratoire Ondes et Matière d'Aquitaine
26 LAM - Laboratoire d'Astrophysique de Marseille

Context. 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 which yielded a central flash detection.
Aims: We aimed at constraining Triton's atmospheric structure and the seasonal variations of its atmospheric pressure since the Voyager 2 epoch (1989). We also derived the shape of the lower atmosphere from central flash analysis.
Methods: We used Abel inversions and direct ray-tracing code to provide the density, pressure, and temperature profiles in the altitude range ~8 km to ~190 km, corresponding to pressure levels from 9 µbar down to a few nanobars.
Results: (i) A pressure of 1.18 ± 0.03 µbar is found at a reference radius of 1400 km (47 km altitude). (ii) A new analysis of the Voyager 2 radio science occultation shows that this is consistent with an extrapolation of pressure down to the surface pressure obtained in 1989. (iii) A survey of occultations obtained between 1989 and 2017 suggests that an enhancement in surface pressure as reported during the 1990s might be real, but debatable, due to very few high S/N light curves and data accessible for reanalysis. The volatile transport model analysed supports a moderate increase in surface pressure, with a maximum value around 2005-2015 no higher than 23 µbar. The pressures observed in 1995-1997 and 2017 appear mutually inconsistent with the volatile transport model presented here. (iv) The central flash structure does not show evidence of an atmospheric distortion. We find an upper limit of 0.0011 for the apparent oblateness of the atmosphere near the 8 km altitude.

Light curves are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/659/A136

Mots clés: methods: data analysis; methods: observational; planets and satellites: atmospheres; planets and satellites: physical evolution; techniques: photometric; Astrophysics - Earth and Planetary Astrophysics

Domaines: Planète et Univers [physics]; Astrophysique [astro-ph]

J. Marques Oliveira, B. Sicardy, A. R. Gomes-Júnior, J. L. Ortiz, D. F. Strobel, et al.. Constraints on the structure and seasonal variations of Triton's atmosphere from the 5 October 2017 stellar occultation and previous observations. Astronomy and Astrophysics - A&A, 2022, 659, pp.1-43. ⟨10.1051/0004-6361/202141443⟩. ⟨insu-03656916⟩