36th DPS Meeting, 8-12 November 2004
Session 46 Asteroid Physical Properties II
Oral, Friday, November 12, 2004, 1:30-3:00pm, Clark

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[46.09] Unusual Lightcurves in the Vesta Family of Asteroids

W. H. Ryan, E. V. Ryan (New Mexico Tech), C. T. Martinez (University of New Mexico)

A photometric survey of the Vesta family of asteroids was undertaken by the authors (beginning in 1999) in an effort to better understand the outcomes of large-scale collisions in the solar system. Although most of the objects studied have displayed the usual doubly periodic curves associated with tri-axial ellipsoids, a few have revealed more unusual features. Observations from 2002, 2003, and 2004 of 3782 Celle displayed anomalous attenuations superimposed on a doubly periodic lightcurve. This result for Celle has been interpreted (Ryan et al. 2003) to represent an asynchronous binary system where the primary is rotating with a 3.87 hour period and the secondary is orbiting with a 36.6 hour period. 3703 Volkonskaya has also displayed a similar lightcurve signature in data obtained in 2000 and 2003 with anomalous attenuations occurring with a periodicity of ~24 hours superimposed on a doubly periodic 3.24 hour structure. However, insufficient data exists to determine whether this 24-hour periodicity is an alias or not. In 2000, 3155 Lee displayed a lightcurve period of 8.31 hours, but with 4 maxima and minima per cycle. Since these variations are grouped in pairs with significantly different amplitudes, it is tempting to also interpret this as a doubly periodic lightcurve with superimposed anomalous attenuations due to the presence of a small satellite. However, since the orbital period would be synchronous with the primary's rotational period, it would be difficult to distinguish this effect from one due to surface features. Since the Vesta family is believed to have been created via a cratering event, analysis of these of unusual objects has important implications for understanding possible ejecta reaccumulation and satellite formation in subcatastrophic collisions.

This work is supported by the NASA Planetary Astronomy Program and the generous observing time made available by the Vatican Observatory Research Group and NOAO.

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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.