Stellar occultations enable milliarcsecond astrometry for Trans-Neptunian objects and Centaurs

¹ Observatório Nacional/MCTIC, R. General José Cristino 77, Bairro Imperial de São Cristóvão, Rio de Janeiro (RJ), Brazil
e-mail: flaviarommel@on.br
² Federal University of Technology - Paraná (UTFPR / DAFIS), Rua Sete de Setembro, 3165, Curitiba (PR), Brazil
³ Laboratório Interinstitucional de e-Astronomia - LIneA & INCT do e-Universo, Rua Gal. José Cristino 77, Bairro Imperial de São Cristóvão, Rio de Janeiro (RJ), Brazil
⁴ Institut Polytechnique des Sciences Avancées IPSA, 63 boulevard de Brandebourg, 94200 Ivry-sur-Seine, France
⁵ Institut de Mécanique Céleste et de Calcul des Éphémérides, IMCCE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ Paris 06, Univ. Lille, 77, Av. Denfert-Rochereau, 75014 Paris, France
⁶ Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
⁷ LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, 92195 Meudon, France
⁸ Observatório do Valongo/UFRJ, Ladeira Pedro Antônio 43, Rio de Janeiro (RJ), Brazil
⁹ Florida Space Institute, University of Central Florida, 12354 Research Parkway, Partnership 1, Orlando, FL, USA
¹⁰ UNESP - São Paulo State University, Grupo de Dinâmica Orbital e Planetologia, CEP 12516-410, Guaratinguetá, SP, Brazil
¹¹ International Occultation Timing Association (IOTA), P.O. Box 423, Greenbelt, MD 20768, USA
¹² Trans-Tasman Occultation Alliance (TTOA), Wellington PO Box 3181, New Zealand
¹³ Canberra Astronomical Society, Canberra, ACT, Australia
¹⁴ Samford Valley Observatory (Q79), Queensland, Australia
¹⁵ Coral Towers Observatory, Cairns, QLD 4870, Australia
¹⁶ Centre of Studies and Activities for Space (CISAS) ’G. Colombo’, University of Padova, Via Venezia 15, 35131, Italy
¹⁷ INAF-Astronomical Observatory of Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
¹⁸ Jewel Box Observatory, 69 Falcon St, Bayview Heights QLD 4868, Australia
¹⁹ SONEAR Observatory, Oliveira (MG), Brazil
²⁰ Department of Physics and Astronomy ’G. Galilei’, University of Padova, Via F. Marzolo 8, 35131, Padova, Italy
²¹ Mount John University Observatory, University of Canterbury, PO Box 56, Lake Tekapo 7945, New Zealand
²² Astronomical Institute, Academy of Sciences of the Czech Republic, Fričova 298, 251 65 Ondřejov, Czech Republic
²³ Astronomical Association of Queensland, 5 Curtis Street, Pimpama QLD 4209, Australia
²⁴ Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France
²⁵ SOTAS – Stellar Occultation Timing Association Switzerland, Swiss Astronomical Society, Switzerland
²⁶ Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Konkoly-Thege Miklós út 15-17, 1121 Budapest, Hungary
²⁷ Eötvös Loránd University, Department of Astronomy, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary
²⁸ ELTE Eötvös Loránd University, Institute of Physics, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary
²⁹ Centro de Amigos de la Astronomia Reconquista – CAAR, Reconquista, Argentina
³⁰ Japan Occultation Information Network (JOIN), Japan
³¹ Reedy Creek Observatory, Gold Coast, Queensland, Australia
³² STAR Institute, Université de Liège, Allée du 6 août, 19C, 4000 Liège, Belgium
³³ Astronomical Institute, Slovak Academy of Sciences, 059 60 Tatranská Lomnica, Slovakia
³⁴ Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Poznan, Poland
³⁵ San Pedro de Atacama Celestial Explorations – SPACE, Chile
³⁶ University of Ljubljana, Faculty of Mathematics and Physics, Jadranska 19, 1000 Ljubljana, Slovenia
³⁷ Panamanian Observatory in San Pedro de Atacama - OPSPA
³⁸ Department of Physics, Sharif University of Technology, PO Box 11155-9161 Tehran, Iran
³⁹ Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ, UK
⁴⁰ Club d’astronomie Luberon Sud Astro, La Bastide des Jourdans, France
⁴¹ Centro de Astronomía (CITEVA), Universidad de Antofagasta, Avenida U. de Antofagasta, 02800 Antofagasta, Chile

Received: 28 July 2020
Accepted: 14 October 2020

Abstract

Context. Trans-Neptunian objects (TNOs) and Centaurs are remnants of our planetary system formation, and their physical properties have invaluable information for evolutionary theories. Stellar occultation is a ground-based method for studying these distant small bodies and has presented exciting results. These observations can provide precise profiles of the involved body, allowing an accurate determination of its size and shape.

Aims. The goal is to show that even single-chord detections of TNOs allow us to measure their milliarcsecond astrometric positions in the reference frame of the Gaia second data release (DR2). Accurate ephemerides can then be generated, allowing predictions of stellar occultations with much higher reliability.

Methods. We analyzed data from various stellar occultation detections to obtain astrometric positions of the involved bodies. The events published before the Gaia era were updated so that the Gaia DR2 stellar catalog is the reference, thus providing accurate positions. Events with detection from one or two different sites (single or double chord) were analyzed to determine the event duration. Previously determined sizes were used to calculate the position of the object center and its corresponding error with respectto the detected chord and the International Celestial Reference System propagated Gaia DR2 star position.

Results. We derive 37 precise astrometric positions for 19 TNOs and four Centaurs. Twenty-one of these events are presented here for the first time. Although about 68% of our results are based on single-chord detection, most have intrinsic precision at the submilliarcsecond level. Lower limits on the diameter of bodies such as Sedna, 2002 KX₁₄, and Echeclus, and also shape constraints on 2002 VE₉₅, 2003 FF₁₂₈, and 2005 TV₁₈₉ are presented as valuable byproducts.

Conclusions. Using the Gaia DR2 catalog, we show that even a single detection of a stellar occultation allows improving the object ephemeris significantly, which in turn enables predicting a future stellar occultation with high accuracy. Observational campaigns can be efficiently organized with this help, and may provide a full physical characterization of the involved object, or even the study of topographic features such as satellites or rings.