The 2017 May 20${}^{\mathrm{th}}$ stellar occultation by the elongated centaur (95626) 2002 GZ${}_{32}$

Abstract

We predicted a stellar occultation of the bright star Gaia DR1 4332852996360346368 (UCAC4 385-75921) (m${}_{\mathrm{V}}$= 14.0 mag) by the centaur 2002 GZ${}_{32}$ for 2017 May 20${}^{\mathrm{th}}$. Our latest shadow path prediction was favourable to a large region in Europe. Observations were arranged in a broad region inside the nominal shadow path. Series of images were obtained with 29 telescopes throughout Europe and from six of them (five in Spain and one in Greece) we detected the occultation. This is the fourth centaur, besides Chariklo, Chiron and Bienor, for which a multi-chord stellar occultation is reported. By means of an elliptical fit to the occultation chords we obtained the limb of 2002 GZ${}_{32}$ during the occultation, resulting in an ellipse with axes of 305 $\pm$ 17 km $\times$ 146 $\pm$ 8 km. From this limb, thanks to a rotational light curve obtained shortly after the occultation, we derived the geometric albedo of 2002 GZ${}_{32}$ ($p_{\mathrm{V}}$ = 0.043 $\pm$ 0.007) and a 3-D ellipsoidal shape with axes 366 km $\times$ 306 km $\times$ 120 km. This shape is not fully consistent with a homogeneous body in hydrostatic equilibrium for the known rotation period of 2002 GZ${}_{32}$. The size (albedo) obtained from the occultation is respectively smaller (greater) than that derived from the radiometric technique but compatible within error bars. No rings or debris around 2002 GZ${}_{32}$ were detected from the occultation, but narrow and thin rings cannot be discarded.

Accepted for publication in MNRAS (8-Dec.-2020), 15 pages, 9 figures

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Cited by in corpus (7)

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• Light curves of transneptunian objects from the K2 mission of the Kepler Space Telescope
• Astrometry with PRAIA
• 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
• Size and shape of the trans-Neptunian object (470316) 2007 OC10: Comparison with thermal data