A study of centaur (54598) Bienor from multiple stellar occultations and rotational light curves^*

¹ Instituto de Astrofísica de Andalucía – Consejo Superior de Investigaciones Científicas (IAA-CSIC), Glorieta de la Astronomía S/N, 18008 Granada, Spain
e-mail: jlrizos@iaa.es
² Florida Space Institute, UCF, 12354 Research Parkway, Partnership 1 building, Room 211, Orlado, USA
³ Federal University of Technology-Paraná (UTFPR/DAFIS), Av. Sete de Setembro, 3165, CEP 80230-901 Curitiba, PR, Brazil
⁴ Laboratório Interinstitucional de e-Astronomia – LIneA – and INCT do e-Universo. Av. Pastor Martin Luther King Jr, 126 Del Castilho, Nova América Offices, Torre 3000/sala 817 CEP: 20765-000, Brazil
⁵ LESIA, UMR8109, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, Meudon 92195, France
⁶ Instituto de Física Aplicada a las Ciencias y las Tecnologías, Universidad de Alicante, San Vicent del Raspeig, 03080 Alicante, Spain
⁷ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, USA
⁸ Institut Polytechnique des Sciences Avancées IPSA, 63 boulevard de Brandebourg, 94200 Ivry-sur-Seine, France
⁹ 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
¹⁰ naXys, Department of Mathematics, University of Namur, Rue de Bruxelles 61, Namur 5000, Belgium
¹¹ Universidade Federal do Rio de Janeiro, Observatório do Valongo, Ladeira Pedro do Antonio 43, Rio de Janeiro, RJ 20.080-90, Brazil
¹² UNESP – São Paulo State University, Grupo de Dinâmica Orbital e Planetologia, Guaratinguetá, SP 12516-410, Brazil
¹³ Observatório Nacional (MCTI), Rua Gal. José Cristino, 77–Bairro Imperial de São Cristóvão, 20921-400 Rio de Janeiro, Brazil
¹⁴ TÜBİTAK National Observatory, Akdeniz University Campus, 07058 Antalya, Turkey
¹⁵ Astronomy Department and Van Vleck Observatory, Wesleyan University, Middletown, CT 06459, USA
¹⁶ Westport Astronomical Society, Westport, CT, USA
¹⁷ Dept of Mathematics and Physics, University of New Haven, West Haven, CT, USA
¹⁸ Salvia Observatory, France
¹⁹ Schreurs O (S.A.L.), Liège, Belgium
²⁰ Société Astronomique de Liège (S.A.L.), Nandrin Observatory, Belgium
²¹ Dourbes, Viroinval, Belgium
²² Tsu Mie, Tsu Mie, Japan
²³ Pressigny, France
²⁴ Uda Nara, Nara, Japan
²⁵ Owase Mie, Nakamuracho, Japan
²⁶ Cottered Observatory, Hertfordshire, England, UK

Received: 22 May 2024
Accepted: 12 July 2024

Abstract

Context. Centaurs, distinguished by their volatile-rich compositions, play a pivotal role in understanding the formation and evolution of the early Solar System, as they represent remnants of the primordial material that populated the outer regions. Stellar occultations offer a means to investigate their physical properties, including shape and rotational state, and the potential presence of satellites and rings.

Aims. This work aims to conduct a detailed study of the centaur (54598) Bienor through stellar occultations and rotational light curves from photometric data collected during recent years.

Methods. We successfully predicted three stellar occultations by Bienor that were observed from Japan, Western Europe, and the USA. In addition, we organized observational campaigns from Spain to obtain rotational light curves. At the same time, we developed software to generate synthetic light curves from three-dimensional shape models, enabling us to validate the outcomes through computer simulations.

Results. We resolved Bienor’s projected ellipse for December 26, 2022; determined a prograde sense of rotation; and confirmed an asymmetric rotational light curve. We also retrieved the axes of its triaxial ellipsoid shape as a = (127 ± 5) km, b = (55 ± 4) km, and c = (45 ± 4) km. Moreover, we refined the rotation period to 9.1736 ± 0.0002 h and determined a geometric albedo of (6.5 ± 0.5)%, which is higher than previously determined by other methods. Finally, by comparing our findings with previous results and simulated rotational light curves, we analyzed whether an irregular or contact-binary shape, an additional element such as a satellite, or significant albedo variations on Bienor’s surface may be present.