Letter to the Editor

Changing material around (2060) Chiron revealed by an occultation on December 15, 2022

¹ Instituto de Astrofísica de Andalucía, Consejo Superior de Investigaciones Científicas, Glorieta de la Astronomía s/n, 18008 Granada, Spain
e-mail: ortiz@iaa.es
² Observatório Nacional/MCTI, R. General José Cristino 77, CEP 20921-400 Rio de Janeiro – RJ, Brazil
³ Laboratório Interinstitucional de e-Astronomia – LIneA, Rio de Janeiro – RJ, Brazil
⁴ LESIA, Observatoire de Paris, Université PSL, Sorbonne Université, Université de Paris, CNRS, 92190 Meudon, France
⁵ Federal University of Technology – Paraná (UTFPR-Curitiba), Rua Sete de Setembro, 3165, CEP 80230-901 Curitiba, PR, Brazil
⁶ National Research Institute of Astronomy and Geophysics (NRIAG), Helwan, 11421 Cairo, Egypt
⁷ The Wise Observatory and the Raymond and Beverly Sackler School of Physics and Astronomy, The Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel
⁸ International Occultation Timing Association – European Section (IOTA/ES), Am Brombeerhag 13, 30459 Hannover, Germany
⁹ Institut Polytechnique des Sciences Avancées IPSA, 63 boulevard de Brandebourg, 94200 Ivry-sur-Seine, France
¹⁰ 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, France
¹¹ Universidade Federal do Rio de Janeiro – Observatório do Valongo, Ladeira Pedro Antônio 43, CEP 20.080-090 Rio de Janeiro – RJ, Brazil
¹² Florida Space Institute, UCF, 12354 Research Parkway, Partnership 1 Building, Room 211, Orlando, FL, USA
¹³ Departments of Astronomy, and of Earth and Planetary Science, 501 Campbell Hall University of California Berkeley, CA 94720, USA
¹⁴ naXys, University of Namur, 8 Rempart de la Vierge, Namur 5000, Belgium
¹⁵ Akdeniz University, Faculty of Sciences, Department of Space Sciences and Technologies, 07058 Antalya, Turkey
¹⁶ TÜBİTAK National Observatory, Akdeniz University Campus, 07058 Antalya, Turkey
¹⁷ Istanbul University, Faculty of Science, Department of Astronomy and Space Sciences, 34116 Beyazıt, Istanbul, Turkey
¹⁸ Instituto de Física Aplicada a las Ciencias y las Tecnologías, Universidad de Alicante, San Vicent del Raspeig, 03080 Alicante, Spain
¹⁹ Institute for Astronomy and Astrophysics, Eberhard Karls University of Tübingen, Tübingen, Germany
²⁰ Orbital Dynamics and Planetology Group, UNESP – São Paulo State University, Guaratinguetá, Brazil

Received: 26 May 2023
Accepted: 21 July 2023

Abstract

We were able to accurately predict the shadow path and successfully observe an occultation of a bright star by Chiron on December 15, 2022. The Kottamia Astronomical Observatory in Egypt did not detect the occultation by the solid body, but we found three extinction features in the light curve that had symmetrical counterparts with respect to the central time of the occultation. One of the features is broad and shallow, whereas the other two features are sharper, with a maximum extinction of ∼25% at the achieved spatial resolution of 19 km per data point. From the Wise Observatory in Israel, we detected the occultation caused by the main body and several extinction features surrounding the body. When all the secondary features are plotted in the sky plane, we find that they can be caused by a broad ∼580 km disk with concentrations at radii of 325 ± 16 km and 423 ± 11 km surrounding Chiron. At least one of these structures appears to be outside the Roche limit. The ecliptic coordinates of the pole of the disk are λ = 151° ±8° and β = 18° ±11°, in agreement with previous results. We also reveal our long-term photometry results, indicating that Chiron had suffered a brightness outburst of at least 0.6 mag between March and September 2021 and that Chiron was still somewhat brighter at the occultation date than at its nominal pre-outburst phase. The outermost extinction features might be consistent with a bound or temporarily bound structure associated with the brightness increase. However, the nature of the brightness outburst is unclear, and it is also unclear whether the dust or ice released in the outburst could be feeding a putative ring structure or whether it is emanating from it.