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New determination of the size and bulk density of the binary Asteroid 22 Kalliope from observations of mutual eclipses |
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| Authors: | P Descamps F Marchis J Pollock F Vachier M Kaasalainen MH Wong EM Cooper P Wiggins M Polinska A Devyatkin D Gorshanov |
| Institution: | a Institut de Mécanique Céleste et de Calcul des Éphémérides, Observatoire de Paris, UMR8028 CNRS, 77 av. Denfert-Rochereau, 75014 Paris, France b University of California at Berkeley, Department of Astronomy, 601 Campbell Hall, Berkeley, CA 94720, USA c Appalachian State University, Department of Physics and Astronomy, 231 CAP Building, Boone, NC 28608, USA d Department of Mathematics and Statistics, Gustaf Hallstromin Katu 2b, P.O. Box 68, FIN-00014 University of Helsinki, Finland e DLR Institute of Planetary Research, Rutherfordstrasse 2, 12489 Berlin, Germany f Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019, USA g Wiggins Observatory, 472 Country Club, Tooele, UT 84074-9665, USA h Astronomical Observatory, Adam Mickiewicz University, Sloneczna 36, 60-286 Poznan, Poland i Observatoire de la Farigourette, 13012 Marseille, France j Central Astronomical Observatory, Pulkovskoe Chaussee 65/1, 196140 St.-Petersburg, Russia k SETI Institute, 515 N. Whisman Road, Mountain View, CA 94043, USA |
| Abstract: | In 2007, the M-type binary Asteroid 22 Kalliope reached one of its annual equinoxes. As a consequence, the orbit plane of its small moon, Linus, was aligned closely to the Sun's line of sight, giving rise to a mutual eclipse season. A dedicated international campaign of photometric observations, based on amateur-professional collaboration, was organized and coordinated by the IMCCE in order to catch several of these events. The set of the compiled observations is released in this work. We developed a relevant model of these events, including a topographic shape model of Kalliope refined in the present work, the orbit solution of Linus as well as the photometric effect of the shadow of one component falling on the other. By fitting this model to the only two full recorded events, we derived a new estimation of the equivalent diameter of Kalliope of 166.2±2.8 km, 8% smaller than its IRAS diameter. As to the diameter of Linus, considered as purely spherical, it is estimated to 28±2 km. This substantial “shortening” of Kalliope, gives a bulk density of 3.35±0.33 g/cm3, significantly higher than past determinations but more consistent with its taxonomic type. Some constraints can be inferred on the composition. |
| Keywords: | Asteroids rotation Asteroids surfaces Satellites of asteroids Eclipses Photometry |
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