Nature of the small main belt Asteroid 3169 Ostro |
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Authors: | P Descamps T Michalowski J Berthier J-P Teng-Chuen-Yu B Payet Y Léonie H Berrouachdi F Benard |
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Institution: | a Institut de Mécanique Céleste et de Calcul des Éphémérides, Observatoire de Paris, F-75014 Paris, France b University of California at Berkeley, Department of Astronomy, 601 Campbell Hall, Berkeley, CA 94720, USA c Astronomical Observatory, Adam Mickiewicz University, Sloneczna 36, 60-286 Poznan, Poland d Les Makes Observatory, 18, rue G. Bizet, Les Makes, F-97421 La Rivière, La Réunion, France |
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Abstract: | We present a set of rotational lightcurve measurements of the small main belt Asteroid 3169 Ostro. Our observations reveal an unambiguous, double-peaked rotational lightcurve with a peak-to-peak variation up to 1.2±0.05 mag and a synodic period of 6.509±0.001 h. From the large flux variation and the overall shape of the lightcurves, we suggest that 3169 Ostro could be a tightly bound binary or a contact binary, similar to the Trojan Asteroid 624 Hektor. A shape model of this system is proposed on the assumption that 3169 Ostro is a Roche binary described by a pair of homogeneous elongated bodies, with a size ratio of 0.87, in hydrostatic equilibrium and in circular synchronous motion around each other. The direction of the spin axis is determined modulo 180° by its J2000 ecliptic coordinates λ0=50±10°, β0=±54±5°. The binary interpretation and the pole solution adequately fit the earlier photometric observations made in 1986 and 1988. However, additional supporting lightcurves are highly desirable especially in the next mutual events occurrence of 2008 and 2009 in order to remove the pole ambiguity and to confirm unambiguously the binary nature of 3169 Ostro. |
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Keywords: | Asteroids Asteroids rotation Asteroids composition Eclipses Occultations |
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