Physical and dynamical properties of the main belt triple asteroid 87 SylviaReportar como inadecuado

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1 IMCCE - Institut de Mécanique Céleste et de Calcul des Ephémérides 2 SETI Institute 3 Astronomical Institute Prague

Abstract : We present the analysis of high angular resolution observations of the triple Asteroid 87 Sylvia collected with three 8-10 m class telescopes Keck, VLT, Gemini North and the Hubble Space Telescope. The moons- mutual orbits were derived individually using a purely Keplerian model. We computed the position of Romulus, the outer moon of the system, at the epoch of a recent stellar occultation which was successfully observed at less than 15 km from our predicted position, within the uncertainty of our model. The occultation data revealed that the Moon, with a surface-area equivalent diameter Ds=23.1±0.7km, is strongly elongated axes ratio of 2.7±0.32.7±0.3, significantly more than single asteroids of similar size in the main-belt. We concluded that its shape is probably affected by the tides from the primary. A new shape model of the primary was calculated combining adaptive-optics observations with this occultation and 40 archived light-curves recorded since 1978. The difference between the J2=0.024-0.009+0.016 derived from the 3-D shape model assuming an homogeneous distribution of mass for the volume equivalent diameter Dv=273±10km primary and the null J2 implied by the Keplerian orbits suggests a non-homogeneous mass distribution in the asteroid-s interior.

Keywords : Asteroids Satellites of asteroids Adaptive optics Photometry Orbit determination Occultations

Autor: Jérôme Berthier - Frédéric Vachier - Franck Marchis - Josef Durech - Benoit Carry -



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