Constraints on (2060) Chiron's size, shape, and surrounding material from the November 2018 and September 2019 stellar occultations

Abstract

After the discovery of rings around the largest known Centaur object, (10199) Chariklo, we carried out observation campaigns of stellar occultations produced by the second-largest known Centaur object, (2060) Chiron, to better characterize its physical properties and presence of material on its surroundings. We predicted and successfully observed two stellar occultations by Chiron. These observations were used to constrain its size and shape by fitting elliptical limbs with equivalent surface radii in agreement with radiometric measurements. Constraints on the (2060) Chiron shape are reported for the first time. Assuming an equivalent radius of R${}_{equiv}$ = 105${}_{-7}^{+6}$ km, we obtained a semi-major axis of a = 126 $\pm$ 22 km. Considering Chiron's true rotational light curve amplitude and assuming it has a Jacobi equilibrium shape, we were able to derive a 3D shape with a semi-axis of a = 126 $\pm$ 22 km, b = 109 $\pm$ 19 km, and c = 68 $\pm$ 13 km, implying in a volume-equivalent radius of R${}_{vol}$ = 98 $\pm$ 17 km, implying a density of 1119 $\pm$ 4 kg m${}^{-3}$. We determined the physical properties of the 2011 secondary events around Chiron, which may then be directly compared with those of Chariklo rings, as the same method was used. Data obtained from SAAO in 2018 do not show unambiguous evidence of the proposed rings, mainly due to the large sampling time. Meanwhile, we discarded the possible presence of a permanent ring similar to (10199) Chariklo's C1R in optical depth and extension. Using the first multi-chord stellar occultation by (2060) Chiron and considering it to have a Jacobi equilibrium shape, we derived its 3D shape. New observations of a stellar occultation by (2060) Chiron are needed to further investigate the material's properties around Chiron, such as the occultation predicted for September 10, 2023.

References in corpus (6)

• A ring system detected around the Centaur (10199) Chariklo
• The thermal emission of Centaurs and Trans-Neptunian objects at millimeter wavelengths from ALMA observations
• Refined physical parameters for Chariklo's body and rings from stellar occultations observed between 2013 and 2020
• The structure of Chariklo's rings from stellar occultations
• Results from the 2014 November 15th multi-chord stellar occultation by the TNO (229762) 2007 UK${}_{126}$
• Characterization of material around the centaur (2060) Chiron from a visible and near-infrared stellar occultation in 2011

Cited by in corpus (6)

• Stellar occultations by Trans-Neptunian Objects
• The rings of (2060) Chiron: Evidence of an evolving system
• Material Around the Centaur (2060) Chiron from the 2018 November 28 UT Stellar Occultation
• The Discovery and Evolution of a Possible New Epoch of Cometary Activity by the Centaur (2060) Chiron
• A study of centaur (54598) Bienor from multiple stellar occultations and rotational light curves
• Constraining the size, shape, and albedo of the large Trans-Neptunian Object (28978) Ixion with multi-chord stellar occultations