The large trans-Neptunian object 2002 TC₃₀₂ from combined stellar occultation, photometry, and astrometry data^★

¹ Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
e-mail: ortiz@iaa.es
² LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, 92195 Meudon, France
³ Laboratório Interinstitucional de e-Astronomia - LIneA, Rua Gal. José Cristino 77, Rio de Janeiro 20921-400, Brazil
⁴ Federal University of Technology-Paraná (UTFPR / DAFIS), Curitiba, Brazil
⁵ Observatório Nacional/MCTIC, Rio de Janeiro, Brazil
⁶ Florida Space Institute, University of Central Florida, 12354 Research Parkway, Partnership 1, Orlando, FL, USA
⁷ Dipartimento di Fisica e Astronomia, ’G. Galilei’, Universita degli Studi di Padova, Padova, Italy
⁸ INAF – Osservatorio Astronomico di Padova, Padova, Italy
⁹ Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France
¹⁰ INAF – Osservatorio di Astrofisica e Scienza dello Spazio, Bologna, Italy
¹¹ Schiaparelli Astronomical Observatory, Varese, Italy
¹² Astronomical Observatory San Marcello Pistoiese CARA Project, Italy
¹³ Crni Vrh Observatory, Crni Vrh nad Idrijo, Slovenia
¹⁴ Faculty of Mathematics and Physics, University of Ljubljana, Slovenia
¹⁵ Osservatorio Astronomico di Monte Agliale, Lucca, Italy
¹⁶ 55 impasse de la Marjolaine, 83560 Vinon sur Verdon, France
¹⁷ Observatorio Astronomico Iota-Scorpii, La Spezia, Italy
¹⁸ 1075 avenue Saint Philippe, 06410 Biot, France
¹⁹ Observatoire de la Côte d’Azur, France
²⁰ Gnosca Observatory, In Fun I Vign 7, 6525, Gnosca, Switzerland
²¹ Osservatorio Astronomico di Tavolaia, Pisa, Italy
²² Institut Polytechnique des Sciences Avancées IPSA, 63 boulevard de Brandebourg, 94200 Ivry-sur-Seine, France
²³ 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
²⁴ Observatório do Valongo/UFRJ, Rio de Janeiro, Brazil
²⁵ International Occultation Timing Association - European Section (IOTA-ES), Germany
²⁶ Observatoire de Geneve, Sauverny, Switzerland
²⁷ Max Planck Institut für extraterrestrische Physik (MPE), Garching, Germany
²⁸ UNESP - São Paulo State University, Grupo de Dinâmica Orbital e Planetologia, Guaratinguetá 12516-410, Brazil
²⁹ German Aerospace Center (DLR), Institute of Planetary Research, Berlin, Germany
³⁰ DFISTS, Universidad de Alicante, Alicante, Spain
³¹ IUFACyT, Unversidad de Alicante, Alicante, Spain
³² University of Zagreb, Faculty of Electrical Engineering and Computing, Unska 3, 10000 Zagreb, Croatia
³³ Physics Division, E.O. Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, 94720 USA
³⁴ Astronomical Observatory of the Autonomous Region of the Aosta Valley (OAVdA), Lignan 39, 11020 Nus, Italy
³⁵ Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Konkoly-Thege Miklós út 15-17, 1121 Budapest, Hungary
³⁶ ELTE Eötvös Loránd University, Institute of Physics, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary
³⁷ Astronomical Institute, Slovak Academy of Sciences, Tatranská Lomnica, Slovakia
³⁸ MTA-ELTE Exoplanet Research Group, 9700 Szombathely, Szent Imre h. u. 112, Hungary
³⁹ ELTE Gothard Astrophysical Observatory, 9700 Szombathely, Szent Imre h. u. 112, Hungary
⁴⁰ Institute for Astronomy, Astrophysics, Space Applications & Remote Sensing, National Observatory of Athens, Athens, Greece
⁴¹ University of Crete, Department of Physics, Heraklion, Greece
⁴² Eötvös Loránd University, Faculty of Science, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary
⁴³ Astronomical Observatory Institute, Faculty of Physics, A. Mickiewicz University, Poznan, Poland
⁴⁴ Nunki Observatory, Greece
⁴⁵ Ellinogermaniki Agogi Observatory, Greece
⁴⁶ Observatorio Astronómico, Universidad de Valencia, Valencia, Spain
⁴⁷ Centro de Estudios de Física del Cosmos de Aragón, Teruel, Spain
⁴⁸ Dpto. de Astrofísica, Universidad de La Laguna, Tenerife, Spain
⁴⁹ Agrupació Astronómica de Sabadell, Barcelona, Spain
⁵⁰ Astrocampania, Osservatorio Salvatore di Giacomo, Agerola (NA), Italy
⁵¹ via Radicosa 44, 80051 Agerola, Italy

Received: 29 March 2020
Accepted: 13 May 2020

Abstract

Context. Deriving physical properties of trans-Neptunian objects is important for the understanding of our Solar System. This requires observational efforts and the development of techniques suitable for these studies.

Aims. Our aim is to characterize the large trans-Neptunian object (TNO) 2002 TC₃₀₂.

Methods. Stellar occultations offer unique opportunities to determine key physical properties of TNOs. On 28 January 2018, 2002 TC₃₀₂ occulted a m_v ~ 15.3 star with designation 593-005847 in the UCAC4 stellar catalog, corresponding to Gaia source 130957813463146112. Twelve positive occultation chords were obtained from Italy, France, Slovenia, and Switzerland. Also, four negative detections were obtained near the north and south limbs. This represents the best observed stellar occultation by a TNO other than Pluto in terms of the number of chords published thus far. From the 12 chords, an accurate elliptical fit to the instantaneous projection of the body can be obtained that is compatible with the near misses.

Results. The resulting ellipse has major and minor axes of 543 ± 18 km and 460 ± 11 km, respectively, with a position angle of 3 ± 1 degrees for the minor axis. This information, combined with rotational light curves obtained with the 1.5 m telescope at Sierra Nevada Observatory and the 1.23 m telescope at Calar Alto observatory, allows us to derive possible three-dimensional shapes and density estimations for the body based on hydrostatic equilibrium assumptions. The effective diameter in equivalent area is around 84 km smaller than the radiometrically derived diameter using thermal data from Herschel and Spitzer Space Telescopes. This might indicate the existence of an unresolved satellite of up to ~300 km in diameter, which is required to account for all the thermal flux, although the occultation and thermal diameters are compatible within their error bars given the considerable uncertainty of the thermal results. The existence of a potential satellite also appears to be consistent with other ground-based data presented here. From the effective occultation diameter combined with absolute magnitude measurements we derive a geometric albedo of 0.147 ± 0.005, which would be somewhat smaller if 2002 TC₃₀₂ has a satellite. The best occultation light curves do not show any signs of ring features or any signatures of a global atmosphere.