A large topographic feature on the surface of the trans-Neptunian object (307261) 2002 MS₄ measured from stellar occultations^★

¹ National Observatory/MCTI, R. General José Cristino 77, CEP20921-400 Rio de Janeiro, Brazil
e-mail: flaviarommel@on.br
² Interinstitutional e-Astronomy Laboratory – LIneA & INCT do e-Universo, Rio de Janeiro, Brazil
³ Federal University of Technology – Paraná (PPGFA/UTFPR – Curitiba), Av. Sete de Setembro 3165, Curitiba, Paraná, Brazil
⁴ Institute of Astrophysics of Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
⁵ LESIA, Paris Observatory, PSL University, CNRS, Sorbonne University, Univ. Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, 92195 Meudon, France
⁶ Polytechnic Institute of Advanced Sciences-IPSA, 63 boulevard de Brandebourg, 94200 Ivry-sur-Seine, France
⁷ Institute of Celestial Mechanics and Ephemeris Calculation (IMCCE), Paris Observatory, PSL Research University, CNRS, Sorbonne University, UPMC Univ Paris 06, Univ. Lille, 77, Av. Denfert-Rochereau, 75014 Paris, France
⁸ Valongo Observatory, Federal University of Rio de Janeiro (UFRJ), Ladeira Pedro Antônio 43 – Saúde, 20080-090 Rio de Janeiro, Brazil
⁹ Orbital Dynamics and Planetology Group, São Paulo State University (UNESP), Av. Ariberto Pereira da Cunha 333, Guaratinguetá, 12516-410 São Paulo, Brazil
¹⁰ Institute of Physics, Federal University of Uberlândia, Uberlândia, Minas Gerais, Brazil
¹¹ Florida Space Institute, University of Central Florida, 12354 Research Parkway, Partnership 1, Orlando, Florida, USA
¹² Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland, USA
¹³ Department of Astronomy, and of Earth and Planetary Science, 501, Campbell Hall, University of California, Berkeley, CA 94720, USA
¹⁴ naXys, Department of Mathematics, University of Namur, Rue de Bruxelles 61, 5000 Namur, Belgium
¹⁵ Domaine de la Blaque Observatory, Domaine de la Blaque, 83670 Varages, France
¹⁶ San Pedro de Atacama Celestial Explorations (SPACE), Chicache 81, Ayllu de Solor, 1410000 San Pedro de Atacama, Chile
¹⁷ Panamanian Observatory in San Pedro de Atacama (OPSPA), Chile
¹⁸ Anarchist Mt. Observatory, British Columbia V0H1V6, Canada
¹⁹ STAR Institute, University of Liège, Allée du 6 aoûtl 19C, 4000 Liège, Belgium
²⁰ Côte d’Azur University, CNRS, Observatoire de la Côte d’Azur, IRD, Géoazur, 250 rue Albert Einstein, Sophia Antipolis 06560 Valbonne, France
²¹ Côte d’Azur Observatory, Géoazur UMR 7329, 2130 Route de l’Observatoire, 06460 Caussols, France
²² University of Zagreb, Faculty of Electrical Engineering and Computing, Department of Applied Physics, Unska 3, 10000 Zagreb, Croatia
²³ Centro Astrononomico Hispano en Andalucía, Observatorio de Calar Alto, Sierra de los Filabres, 04550 Gérgal, Spain
²⁴ Hvar Observatory, Faculty of Geodesy, University of Zagreb, Kaciceva 26, 10000 Zagreb, Croatia
²⁵ Gemini Observatory/NSF’s NOIRLab, Casilla 603, La Serena, Chile
²⁶ Konkoly Observatory, Research Centre for Astronomy and Earth Sciences (ELKH), Konkoly Thege Miklos út 15–17, 1121 Budapest, Hungary
²⁷ CSFK, MTA Centre of Excellence, Konkoly Thege Miklós út 15–17, 1121 Budapest, Hungary
²⁸ Algiers Observatory, CRAAG, Route de l’Observatoire, Algiers, Algeria
²⁹ Odesa I. I. Mechnikov National University, Astronomical Observatory, Marazliivska 1v, 65014 Odesa, Ukraine
³⁰ Main astronomical observatory of National Academy of Sciences of Ukraine, 27 Akademika Zabolotnoho St., 03143 Kyiv, Ukraine
³¹ Department of Astronomy and Space Sciences, Faculty of Science, Istanbul University, 34116 Istanbul, Turkey
³² Istanbul University Observatory Research and Application Center, 34116 Istanbul, Turkey
³³ Research Centre for Astronomy, Astrophysics and Astrophotonics, Department of Physics and Astronomy, Macquarie University, 2109 Sydney, Australia
³⁴ ARC Centre of Excellence for All-Sky Astrophysics in 3 Dimensions, Stromlo, Australian Capital Territory, Australia
³⁵ Çanakkale Onsekiz Mart University, School of Graduate Studies, Department of Physics, 17100 Çanakkale, Turkey
³⁶ Çanakkale Onsekiz Mart University, Astrophysics Research Center and Ulupinar Observatory, 17100 Çanakkale, Turkey
³⁷ International Occultation Timing Association – European Section (IOTA-ES), Am Brombeerhag 13, 30459 Hannover, Germany
³⁸ Sabadell Astronomical Association, Carrer Prat de la Riba, s/n, 08206 Sabadell, Catalonia, Spain
³⁹ PSTJ astronomy club, CIV 190 Rue Frédéric Mistral, 06560 Valbonne, France
⁴⁰ British Astronomical Association (BAA), 25 Farringdon Street, London EC4A 4AB, UK
⁴¹ AstroCampania Association, Via Servio Tullio n. 101, 80126 Naples, Italy
⁴² Instituto de Física Aplicada a las Ciencias y las Tecnologías, Alicante University, San Vicente del Raspeig, 03080 Alicante, Spain
⁴³ Institut de Ciències del Cosmos (ICCUB), Barcelona University (IEEC-UB), Carrer de Martí i Franquès 1, 08028 Barcelona, Spain
⁴⁴ Ponta Grossa State University, Av. Carlos Cavalcanti 4748, Ponta Grossa, Paraná, Brazil
⁴⁵ Department of Earth, Atmospheric and Planetary Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, USA
⁴⁶ Astrobiology Research Unit, University of Liège, Allée du 6 août 19C, 4000 Liège, Belgium
⁴⁷ Canary Islands Institute of Astrophysics (IAC), Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
⁴⁸ INAF – Catania Astrophysical Observatory, via S. Sofia 78, 95123 Catania, Italy
⁴⁹ Campo Catino Astronomical Observatory, Località Colle Pannunzio, 03016 Guarcino (FR), Italy
⁵⁰ Institute of Astronomy of V.N. Karazin Kharkiv National University, Kharkiv 61022, Sumska str. 35, Ukraine
⁵¹ Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Słoneczna 36, 60-286 Poznan, Poland
⁵² Crni Vrh Observatory, Predgriže 29A, 5274 Crni Vrh nad Idrijo, Slovenia
⁵³ University of Ljubljana, Faculty of Mathematics and Physics, Jadranska 19, 1000 Ljubljana, Slovenia
⁵⁴ Pistoiese Mountain Astronomical Observatory (GAMP), San Marcello Pistoiese, Italy
⁵⁵ Astronomical Association of Eivissa (AAE), Lucio Oculacio 29, 07800 Ibiza, Spain
⁵⁶ Monte Agliale Astronomical Observatory, Via Cune Motrone, 55023 Borgo a Mozzano, Italy
⁵⁷ QOS Observatory, Center for Special Information Reception and Processing and Navigation Field Control, National Space Facilities Control and Test Center, Zalistsi village, 32444 Kamianets-Podilskyi district, Khmelnytskyi region, Ukraine
⁵⁸ La Laguna University (ULL), Astrophysics department, Avenida Astrofísico Francisco Sánchez, s/n, Facultad de Ciencias, Sección de Física, 38200 La Laguna, Tenerife, Spain
⁵⁹ Virtual Telescope Project, Via Madonna de Loco 47, 03023 Ceccano, Italy
⁶⁰ G. Pascoli Observatory (MPC K63), Via dei Pieri 1, 55051 Castelvecchio Pascoli, Italy
⁶¹ Red ASTRONAVARRA sarea, 25250 Bellpuig, Catalunha, Spain
⁶² Club Astrospace Thales Alenia Space, 5 Allée des Gabians BP 99, 06156 Cannes, France
⁶³ University of Lille, Lille Observatory, 1 impasse de l’observatoire, 59000 Lille, France
⁶⁴ Tavolaia Observatory (MPC A29), Via Tavolaia, 4, 56020 Santa Maria a Monte, Pisa, Italy
⁶⁵ Romanian Society for Cultural Astronomy - SRPAC, Coriolan Baran st., 300238 Timisoara, Romania
⁶⁶ EPT Observatories, Camino El Pinar, 114, 38780 Tijarafe, Spain
⁶⁷ Penticton Secondary School, 158 Eckhardt Ave East Penticton, British Columbia, Canada
⁶⁸ OACM Observatory, Fuensanta de Martos, pueblo de Jaen, Spain
⁶⁹ Associazione Astrofili Fiorentini (A.A.F.), Via Giulio Caccini 13b, 50141 Firenze, Italy
⁷⁰ Astronomical Society of Southern Africa, Centurion, South Africa
⁷¹ Nastro Verde Astronomical Observatory, Via Nastro Verde 50, Sorrento, Italy
⁷² Cosmos Observatory, Calle Cardenal Pedro Gonzalez, 29604 Marbella, Spain
⁷³ INAF – Trieste Astrophysical Observatory, via G. B. Tiepolo 11, 34143 Trieste, Italy
⁷⁴ Lowell Observatory, 1400 Mars Hill Road, Flagstaff, 86001-4470 Arizona, USA
⁷⁵ ROASTERR, 1 Observatory, Cluj-Napoca, Romania
⁷⁶ PS Observatory (MPC M35), Parjol, Bacau county, Bacau, Romania
⁷⁷ The American Association of Variable Star Observers (AAVSO), 185 Alewife Brook Parkway, Suite 410, Cambridge, MA 02138, USA
⁷⁸ ALMO Observatory via Forlai 14/C, 40010 Sala Bolognese, Bologna, Italy
⁷⁹ UAI (Union of Italian Amateur Astronomers) c/o Osservatorio Astronomico “F. Fuligni” Via Lazio 14, 00040 Rocca di Papa, Roma, Italy
⁸⁰ Telescope Live, 71–75 Shelton Street, Covent Garden, London WC2H 9JQ, UK
⁸¹ Bucharest Astroclub, Bd. Lascar Catargiu 21, 010662 Bucharest, Romania
⁸² Astronomical society of Tunisia (SAT), physics department, faculty of science of Tunis, Campus universitaire, 2092 El Manar, Tunis, Tunisia
⁸³ University of Tunis El Manar, University Campus Farhat Hached, B.P. 94, Rommana, 1068 Tunis, Tunisia
⁸⁴ Ad Astra Sangos Observatory (MPC Z07), Calle Hernán Cortés 4, Alhendín, Granada, Spain
⁸⁵ Sociedad Astronómica Granadina, Avenida de Barcelona 20, 10C, 18006 Granada, Spain
⁸⁶ Stardust Observatory, 3 Alexandru cel Bu, 500260 Brasov, Romania
⁸⁷ Bârlad Astronomical Observatory, Republicii Street 235, 731070 Bârlad, Vaslui County, Romania
⁸⁸ Astronomical Institute of the Romanian Academy, Bucharest, 5 Cuţitul de Argint, 040557 Bucharest, Romania
⁸⁹ Mississippi State University, 295 Lee Blvd Mississippi State, MS 39762 USA
⁹⁰ 113 Kentucky Ave SW, Orange City, Iowa 51041, USA
⁹¹ Syrma-GUA, Paseo de Belén, 9, 47011 Valladolid, Spain
⁹² Department of Space Sciences and Technologies, Akdeniz University, Campus, Antalya 07058, Turkey
⁹³ TÜBİTAK National Observatory, Akdeniz University Campus, Antalya 07058, Turkey
⁹⁴ Euraster, 8 rue du tonnelier, 46100 Faycelles, France
⁹⁵ IRAP, Midi-Pyrenees Observatory, CNRS, University of Toulouse, BP 4346, 31028 Toulouse Cedex 04, France
⁹⁶ Dax Observatory, rue Pascal Lafitte, 40100 Dax, France
⁹⁷ El Leoncito Astronomical Complex, National Council for Scientific and Technical Research, San Juan, Argentina
⁹⁸ National University of La Plata, Facultad de Ciencias Astronómicas y Geofísicas, Paseo del Bosque s/n, B1900FWA La Plata, Argentina
⁹⁹ National University of La Plata, Instituto de Astrofísica de La Plata (CCT La Plata – CONICET/UNLP), B1900FWA La Plata, Argentina
¹⁰⁰ University Observatory, Ludwig-Maximilians, Munich University, Scheiner Str. 1, 81679 Munich, Germany
¹⁰¹ Astronomical Institute, Slovak Academy of Sciences, 05960 Tatranská Lomnica, Slovakia
¹⁰² G. V. Schiaparelli Astronomical Observatory, Campo dei Fiori, Varese, Italy
¹⁰³ Hieronymusstr. 15b, 81241 Munich, Germany
¹⁰⁴ National Astrophiscs Institute, Padova Astronomical Observatory, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
¹⁰⁵ Aix Marseille University, CNRS, CNES, LAM, Marseille 13007, France
¹⁰⁶ Astronomical Institute of the Czech Academy of Sciences, Fricova 1, 25165 Ondrejov, Czech Republic
¹⁰⁷ Adiyaman University, Department of Physics, 02040 Adiyaman, Turkey
¹⁰⁸ Astrophysics Application and Research Center, Adiyaman University, Adiyaman 02040, Turkey
¹⁰⁹ Ataturk University, Department of Astronomy and Space Science, Yakutiye, 25240 Erzurum, Turkey
¹¹⁰ Max-Planck-Institut für extraterrestrische Physik, Giessenbach-strasse, 85748 Garching, Germany
¹¹¹ Sybilla Technologies, Torunska 59, 85-023 Bydgoszcz, Poland
¹¹² Mt. Suhora Observatory, Pedagogical University of Cracow, Podchorazych 2, 30-086 Cracow, Poland
¹¹³ Polytechnic Institute of Tomar, Ci2–Smart Cities Research Center and Unidade Departamental de Matemática e Física (UDMF), 2300 Tomar, Portugal
¹¹⁴ Aristotle University of Thessaloniki (AUTh), University Campus, 54124 Thessaloniki, Greece
¹¹⁵ Centro Ciência Viva de Constância-Parque de Astronomia, Alto de Santa Bárbara, Via Galileu Galilei 817, 2250-100 Constância, Portugal
¹¹⁶ Bülach Observatory (MPC 167), Schul- und Volkssternwarte Bülach, Postfach 540, 8180 Bülach, Switzerland
¹¹⁷ Stellar Occultation Timing Association Switzerland (SOTAS), Swiss Astronomical Society, Schweizerische Astronomische Gesellschaft SAG-SAS, Fachgruppe Sternbedeckungen/SOTAS, 8200 Schaffhausen, Switzerland
¹¹⁸ Türksat Observatory – Türksat Company Headquarters Campus, Yaglipinar Mahallesi Türksat (Küme Evler) İdari Bina Apt. No:1, Gölbaşi, Ankara, Turkey
¹¹⁹ Çukurova University, Department of Astronomy and Astrophysics, Çukurova Üniversitesi Rektörlüğü, 01330 Sariçam/Adana, Turkey
¹²⁰ Adana Yuregir Science Center and Mesopotamia Astronomy Association, Adana, Turkey
¹²¹ Teplice Observatory, North-Bohemian Observatory and Planetarium in Teplice, Koperníkova 3062, 41501 Teplice, Czech Republic
¹²² EUR ING, Hviezdoslavova 1971, 022 01 Cadca, Slovakia
¹²³ GiaGa Observatory, 20005 Pogliano Milanese, Milan, Italy
¹²⁴ Filzi School, Passaggio Maria Damian 20, 39055 Laives, Italy
¹²⁵ Amateur Astronomical Observatory of Seysses, 700 chemin du Fourtané, 31600 Seysses, France
¹²⁶ The Pleiades Latrape Observatory, Grand Rue, 31310 Latrape, France
¹²⁷ Herne Observatory, Am Böckenbusch 2a, 44652 Herne, Germany
¹²⁸ Board of Polish Amateur Astronomers Society, Krakow, Poland
¹²⁹ Polish Astronomical Society, Warsaw, Poland
¹³⁰ ul. Krokusowa 6, 16-001 Ksiezyno, Poland
¹³¹ French Astronomical Society (SAF), 3 rue Beethoven, 75016 Paris, France
¹³² KYSUCE Observatory (MPC G02), Kysucke Nove Mesto, Slovakia
¹³³ Czech Astronomical Society, Fričova 298, 251 65 Ondřejov, Czech Republic
¹³⁴ Observatory in Rokycany and Pilsen, Voldušská 721, 33701 Rokycany, Czech Republic
¹³⁵ ADAGIO Association, Belesta Observatory (MPC A05), 550 route des étoiles, 31540 Bélesta en Lauragais, Toulouse, France
¹³⁶ El Gato Gris Astronomical Observatory (MPC I19), Tanti, 5013 Córdoba City, Argentina
¹³⁷ Grupo de Observadores de Rotaciones de Asteroides (GORA), 5013 Córdoba City, Argentina
¹³⁸ Proyecto de Observación Colaborativa y Regional de Ocultaciones Asteroidales (POCROA), 5013 Córdoba City, Argentina
¹³⁹ El Catalejo Observatory (MPC I48), 6300 Santa Rosa, La Pampa, Argentina
¹⁴⁰ Planetary Science Institute, 1700 East Fort Lowell Road, Suite 106, Tucson, AZ 85719, USA
¹⁴¹ Applied Physics, Bilbao School of Engineering, University of País Vasco, UPV/EHU, Bilbao, Spain
¹⁴² University of Oregon, Department of Physics, 120 Willamette Hall, 1371 E 13th Avenue Eugene, OR, USA
¹⁴³ Purdue University Northwest, Department of Chemistry and Physics, 2200 169th, St Hammond, IN 46323, USA
¹⁴⁴ Vasile Urseanu Observatory (MPC A92), 21 Lascar Catargiu, 010662 Bucharest, Romania
¹⁴⁵ Eskişehir Technical University, Observatory on Yunusemre Campus Science Faculty, Physics Department, 26470 Tepebaşl Eskişehir, Turkey
¹⁴⁶ Section of Astrophysics, Astronomy and Mechanics, Department of Physics, National and Kapodistrian University of Athens, 15784 Zografos, Athens, Greece
¹⁴⁷ Institut für Astronomie und Astrophysik, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
¹⁴⁸ Ondokuz Mayis University Observatory, Kurupelit Campus, 55139 Atakum, Samsun, Turkey
¹⁴⁹ Institute of Space Sciences (CSIC-IEEC), Campus UAB, Carrer de Can Magrans s/n, 08193 Cerdanyola del Vallès, Catalonia, Spain
¹⁵⁰ Sparta Astronomy Association, 22 Amyklon str., 152 31 Halandri, Greece
¹⁵¹ NOAK Observatory (MPC L02), Ioannina, Stavraki Delfon 2, 45500 Greece
¹⁵² Department of Physics, University of Ioannina, Ioannina 45110, Greece
¹⁵³ g-ral Gheorghe Magheru Blvd, no.7, sc.1, ap. 4, Sector 1, Bucharest 010322, Romania
¹⁵⁴ Los Cabezones Observatory (MPC X12), Santa Rosa, La Pampa, Argentina
¹⁵⁵ University of Idaho, Department of Physics, Stop 440903, Moscow, ID 83843, USA
¹⁵⁶ Department of Space Studies, University of North Dakota, 4149 University Avenue Stop 9008, Grand Forks, ND 58202-9008, USA
¹⁵⁷ Chagrin Valley Astronomical Society, 15701 Huntley Rd, Huntsburg, OH 44046, USA
¹⁵⁸ Astronomy Department, University of Chile, Camino del Observatorio 1515, Casilla 36-D, Las Condes, Santiago, Chile
¹⁵⁹ Centro de Excelencia en Astrofísica y Tecnologías Afines (CATA), Chile
¹⁶⁰ Millenium Institute of Astrophysics (MAS), Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile
¹⁶¹ Institute of Space Science, 409 Atomistilor Street Magurele, 077125 Ilfov, Romania
¹⁶² Squirrel Valley Observatory (MPC W34), 3870 River Rd., Columbus, NC 28722, USA
¹⁶³ Department of Physics and Astronomy, University of North Carolina Asheville, 1 University Heights, Asheville, NC 28804, USA

Received: 12 May 2023
Accepted: 1 August 2023

Abstract

Context. The physical characterization of trans-Neptunian objects is essential for improving our understanding of the formation and evolution of our Solar System. Stellar occultation is a ground-based technique that can be successfully used to determine some of the TNOs’ fundamental physical properties with high precision, such as size and shape.

Aims. This work is aimed at constraining the size, shape, and geometric albedo of the dwarf planet candidate (307261) 2002 MS₄ through the analysis of nine stellar occultation events. Using multichord detection, we also study the object’s topography by analyzing the obtained limb and residuals between the observed chords and the best-fit ellipse.

Metods. We predicted and organized the observational campaigns of nine stellar occultations by 2002 MS₄ between 2019 and 2022, resulting in two single-chord events, four double-chord detections, and three events with between 3 and 61 positive chords. We derived the occultation light curves using differential aperture photometry, from which the star ingress and egress instants were calculated. Using 13 selected chords from the 8 August 2020 event, we determined the global elliptical limb of 2002 MS₄. The best-fit ellipse, combined with the object’s rotational information from the literature, sets constraints on the object’s size, shape, and albedo. Additionally, we developed a new method to characterize the topography features on the object’s limb.

Results. The global limb has a semi-major axis of a′ = 412 ± 10 km, a semi-minor axis of b′= 385 ± 17 km, and the position angle of the minor axis is 121° ± 16°. From this instantaneous limb, we obtained 2002 MS₄’s geometric albedo of p_V = 0.1 ± 0.025, using H_V = 3.63 ± 0.05 mag and a projected area-equivalent diameter of 796 ± 24 km. Significant deviations from the fitted ellipse in the northernmost limb were detected from multiple sites, highlighting three distinct topographic features: one 11 km depth depression, followed by a 25₋₅⁺⁴ km height elevation next to a crater-like depression, with an extension of 322 ± 39 km and 45.1 ± 1.5 km deep.

Conclusions. Our results indicate the presence of an object that is ≈138 km smaller in diameter than that derived from thermal data, possibly indicating the presence of a thus-far unknown satellite. However, within the error bars, the geometric albedo in the V-band is in agreement with the results published in the literature, even with the radiometric-derived albedo. This stellar occultation has allowed for the first multichord measurement of a large topography in a TNO.